Talk:Bipolar junction transistor

Polarity of germanium transistors
Were most germanium transistors, PNP transistors? Were NPN germanium transistors uncommon? 24.26.128.185 (talk) 22:07, 25 April 2008 (UTC)

Answer: generally speaking, Yes, and Yes.

"..when a positive voltage is applied to the base–emitter junction.."
If the positive voltage is less than 0.6V for a silicon BJT, the junction does not have enough voltage to forward bias it, and no current will flow. The sentence should read "when a current flows between the base and emitter.." or "..if enough positive voltage is applied to the base-emitter junction to cause a current to flow..". One has to remember that the BJT is a current operated device. July 25, 2012 by Watson - my yahoo email account is acmefixer. Acmefixer (talk) 14:59, 25 July 2012 (UTC)

No, it's a voltage controlled device, it's only incidental that the leakage current is proportional to the Emitter-Collector current. 24.121.250.13 (talk) 15:35, 30 September 2012 (UTC)

external reference bjt_models.pdf gone
The link www.brookdale.cc.nj.us/fac/engtech/aandersen/engi242/bjt_models.pdf should be updated to a new location or removed. —Preceding unsigned comment added by 130.225.243.80 (talk) 20:31, 10 August 2008 (UTC)
 * The correct (new) URL appears to be http://ux.brookdalecc.edu/fac/engtech/andy/engi242/bjt_models.pdf. --TedPavlic | (talk) 20:46, 11 September 2008 (UTC)

Ambiguity and repetition
The sentence "This gain is usually 100 or more, but most robust designs only depend on it being very large" is ambiguous. It just doesn't make much sense and should be reorganized.

Section 5.1.1 Ebers–Moll model is redundant with Section 1.2 Transistor 'alpha' and 'beta'. The same concepts and the same equations are presented. One of the two sections should be merged into the other one. I would myself merge 1.2 into 5.1.1.

ICE77 (talk) 05:49, 19 April 2009 (UTC)


 * Yeah, not great. I worked on it some.  I notice the Ebers–Moll section had this emitter efficiency thing disconnected from anything else since this edit back in 2006; I took it out; but there remains an undefined symbol in the base current density formula that might be related; find a source and work on it? Dicklyon (talk) 06:34, 19 April 2009 (UTC)

The sentence "This gain is usually 100 ..." is repeated twice. You fixed the first occurrence but not the second.

I don't know what you are referring to with "emitter efficiency thing disconnected" and "undefined symbol in the base current density formula". Be more explicit so I can see what you are talking about.

ICE77 (talk) 00:36, 4 May 2009 (UTC)


 * I had removed this bit: "Emitter Efficiency, $$\eta = \frac{J_n(\text{base})}{J_{\text{E}}}$$, is the ratio of current injected into the base to the current in the emitter; the two differ due to backward injection from the base into the emitter and to recombination. See carrier generation and recombination." as it didn't connect to anything, as far as I could tell.


 * There's still a $$n_{bo}$$ in the formula, and I don't know what it is; the section doesn't say; I haven't tried consulting sources yet. Maybe this n was supposed to be the eta thing that I had removed?  Dicklyon (talk) 05:39, 4 May 2009 (UTC)

$$\eta$$ is just a ratio of currents. $$n_{bo}$$ most likely refers to the concentration of electrons (n) in the base (b) of an NPN transistor at equililbrium (o) since electrons are minority carriers in the base of an NPN transistor and they are responsible for current in the device.

ICE77 (talk) 23:46, 5 May 2009 (UTC)


 * Plausible guesses, but neither was connected to anything else in the section, so what we really need is a source; so far I don't see these symbols or anything like them in sources. nbo does look like a carrier density, since it multiplies q. Dicklyon (talk) 04:19, 6 May 2009 (UTC)

Concentration of electrons or holes and electron charge can coexist within a current equation. I have taken notes from a semiconductor book where $$q$$ and $$n$$ or $$q$$ and $$p$$ are multiplied to obtain a current. $$q$$ is just a constant. An example of an equation where this is true is the equation for resistivity.

ICE77 (talk) 23:45, 6 May 2009 (UTC)

A simple model of the transistor consisting of an LED and a photodiode
the following section was deleted on may 20, only one day after it went up: "A simple model with many of the properties of a transistor, especially a phototransistor, is a forward biased LED (emitter–base junction) and a reverse biased photodiode (base–collector junction) sharing an anode (base) in a single package so that 99% (1-1/βF) of the photons emitted by the LED are absorbed by the photodiode. Each electron-hole recombination in the LED produces one photon and each photon absorbed by the photodiode produces one electron-hole pair therefore each electron injected into the base would result in 100 (βF) electrons at the collector". I will leave this copy here so others can discuss whether it should or should not be included in the article. just-emery (talk) 16:25, 20 May 2009 (UTC)


 * This is a complicated passage, and it would take me a lot of time to figure out if this is a useful model or not. Things that require serious thoughts by people experienced in the field to figure out should not be made up by Wikipedia editors; they should come from reliable published sources. --Jc3s5h (talk) 16:35, 20 May 2009 (UTC)
 * It is trivial. If you think its complicated then you are in no position to be judging it. I do not claim that it has all of the properties of a transistor but it obviously does amplify the current. Any high school freshman can see that. just-emery (talk) 16:40, 20 May 2009 (UTC)


 * Go read Verifiability. Since you have no source for this, I will resist the inclusion of this passage. Remember, you may think you are an expert, you may even be an expert, but Wikipedia readers have no way to know who you are. --Jc3s5h (talk) 17:12, 20 May 2009 (UTC)


 * You are trying to confuse the issue. The issue is why on earth this trivial model, which obviously works and makes it easy for beginners to understand (which is what wikipedia is supposed to be about) the operation of the transistor, should be excluded from the article. just-emery (talk) 06:22, 22 May 2009 (UTC)


 * 10,000 electrons injected into the base results in 10,000 electrons appearing at the collector and 10,000 photons created by the led. 9900 of the photons are absorbed by the photodiode which creates 9900 more electrons which travel to the LED and create 9900 more photons and then the electrons move on to the colloctor. 9801 photons are then absorbed by the photodiode. and so on. in the end 100*10,000 electrons reach the collector. 100 times more than was initially injected. 100 fold amplification. just-emery (talk) 06:22, 22 May 2009 (UTC)


 * It's unclear to me how this example aids in the understanding of a bipolar transistor. That is, would a novice who could grok this example easily be able to transition to the more accurate descriptions of diffusion and drift currents? After all, this sort of feedback process cannot be described so explicitly in a BJT (try giving such a feedback explanation WITHOUT using photons). In a BJT, a field is used to turn off the natural dipole that is created by bipolar diffusion; without the dipole, the diffusion can continue and the BJT acts like a current source (where the voltage it displaces is ohmic loss across the base–collector depletion region that narrows and widens as necessary). That's not only the conventional way of understanding bipolar operation, but it is not that technical. We should stick to conventional explanations that can be found in trusted sources (e.g., textbooks). If you think your photon model is a compelling way of explaining BJTs, you should try to find it in an existing textbook and reference it. If you can't find it, you should submit your novel example to a textbook writer. When your example comes out in print, then some other Wikipedia editor will be able to use it and reference it. &mdash;TedPavlic (talk) 13:00, 22 May 2009 (UTC)


 * The purpose of a model is simplicity, not accuracy. just-emery (talk) 15:15, 26 May 2009 (UTC)


 * Your model lacks both simplicity and accuracy, and that's what makes it misleading. You are building fictitious behaviors on top of existing sophisticated devices, namely photodiodes and p–n junctions. You cannot be so cavalier as an encyclopedia editor because readers of the encyclopedia count on you to reflect information that can be verified by a large consensus of experts in the field. There is a great risk that someone may misread your highly inaccurate description as a statement of fact. In the end, the essence of your description is that a transistor provides amplification. There is no reason to posit some mechanism for that amplification if it is not the actual mechanism being used. &mdash;TedPavlic (talk) 17:15, 26 May 2009 (UTC)

Minority carrier device
The BJT is a minority carrier device because most of the charge cariers passing through the control region, the base, are minority carriers with respect to the base. However, it is wrong to say it is a minority carrier device on account of the base current, becase "base current" is taken to mean the current in or out of the base terminal. The base terminal current is not what gets the job done (in the active region); the job gets done by the collector and/or emitter current. Therefore the classification of the device is based on the collector or emitter current. --Jc3s5h (talk) 00:15, 29 June 2009 (UTC)
 * I see. So "base current" to you refers to the current coming out of the base rather than the large concentration of minority carrier current going up from the base into the collector. Well, you're the boss. Revised. &mdash;TedPavlic (talk) 15:58, 29 June 2009 (UTC)


 * That's true; base current is defined as the current into the base terminal. The collector current can perhaps be called the base–collector current, which is what you probably meant to refer to.  Dicklyon (talk) 07:06, 30 June 2009 (UTC)

I probably learned that "minority carrier device" factoid decades ago in my devices class, but has it proved to be useful since then in any of my work with BJTs? I would say definitely not. Acmefixer (talk) 15:07, 25 July 2012 (UTC)

Active-mode PNP transistors in circuits figure incorrect
There is a miror error on the figure associated with the section entitled, "Active-mode PNP transistors in circuits". The arrow indicating the directional flow of the base current "Ib" should point away from the transistor, not toward it. —Preceding unsigned comment added by 199.181.136.59 (talk) 15:49, 1 July 2009 (UTC)

The $6 Man
As one who can barely understand the technobabble on the page, ;D can somebo clarify: is the point-contact design mentioned the same as (or equivalent to) what I've seen described as a "cuprous-contact rectifier"? If not, how do they differ? ("In English, McGee.")  TREKphiler   hit me ♠  09:37, 20 November 2009 (UTC)

Germanium Transistor Section
Hi, I would ask that the Germanium Transistor section be changed from:

The germanium transistor was more common in the 1950s and 1960s, and while it exhibits a lower "cut off" voltage, typically around 0.2 V, making it more suitable for some applications, it also has a greater tendency to exhibit thermal runaway.

to:

The germanium transistor was more common in the 1950s and 1960s, and while it exhibits a lower "turn on" voltage (Vbe), typically around 0.2 V, making it more sensitive, it also has a greater tendency to exhibit thermal runaway. —Preceding unsigned comment added by 64.16.215.100 (talk) 21:26, 28 May 2010 (UTC)

A forward biased germanium PN junction is about 0.4V, compared to 0.7V for silicon. I think that Vce is also lower for a saturated transistor, but haven't though about this recently. Both can sometimes be an advantage. Gah4 (talk) 03:30, 17 June 2019 (UTC)

Ebers-Moll model for a PNP transistor
In the equivalent circuit diagram for the Ebers-Moll model of a PNP transistor, aren't the two diodes shown facing the wrong direction? Shouldn't the cathode of the diode (with the bar) be on the base (n-region) of the transistor? 76.120.125.115 (talk) 04:35, 18 August 2010 (UTC)
 * Yes, I used an old version of the PNG. Sorry about that, fixed Inductiveload (talk) 12:39, 22 August 2010 (UTC)

Ebers-Moll model for NPN transistor
In the Ebers–Moll Model for an NPN transistor I think that αR IED should be αR ICD. Further αF ICD should be αF IED. —Preceding unsigned comment added by 78.33.14.67 (talk) 08:53, 29 October 2010 (UTC)
 * Based on my recollection and page 328 of Ben Streetman's Solid State Electronic Devices (1972) I agree with 78.33.14.67. Jc3s5h (talk) 12:40, 29 October 2010 (UTC)

"The unapproximated Ebers–Moll equations used to describe the three currents in any operating region are given below. These equations are based on the transport model for a bipolar junction transistor"

I am checking this model according this lecture, which appears to be ok for me: https://inderjitsingh87.weebly.com/uploads/2/1/1/4/21144104/the__ebers-moll_bjt_model.pdf

But i fail to reach the same result in the unapproximated case. In fact i think the included equations should explicitly include both ISC and ISE reverse saturation currents, instead a generic IS term.

Can somebody verify i am wrong or right, in order to introduce the proper change in the equations?

Hyprwfrcp (talk) 02:39, 23 April 2018 (UTC)


 * I haven't worked with these equations for a long time, but I find the following definition for IS in Ian Getreu's "Modeling the Bipolar Transisitor" (Beaverton OR: Textronix, 1976) page 14:


 * ...The number of parameters is reduced by one when the reciprocity principle is applied. The principle is defined by:
 * $$\alpha_F I_{ES} = \alpha_r I_{CS} \equiv I_S $$


 * Does that resolve your issue? Jc3s5h (talk) 12:44, 23 April 2018 (UTC)

complexity
The article is accurate however it is impossible to understand unless you already understand how a transistor works. It would be benificial to refer out to the transistor wiki page which gives the required backgroud knowlage to fully understand this page —Preceding unsigned comment added by 195.33.114.129 (talk) 13:52, 10 February 2011 (UTC)

There is a Wikipedia page in "Simple English" which is no more than a stub. Would this be an appropriate place to explain things? — Preceding unsigned comment added by 76.254.24.27 (talk) 01:20, 26 June 2016 (UTC)

Hybrid-pi and h-parameter models
I believe this article should not point to the "hybrid-pi model" article but include it into itself. It's the most important small-signal model. I don't see why the "h-parameter model" should be shown and the "hybrid-pi model" shouldn't. I rather prefer to see the opposite situation which is much more practical.

ICE77 (talk) 18:59, 21 April 2011 (UTC)

Graph
In the graph of the operating characteristics, shouldn't the CE voltage be labeled with a "V" instead of a "U"? This seems confusing.67.141.18.62 (talk) 02:26, 2 June 2012 (UTC)

Schematic is wrong
Please take a look at this page: http://www.markallen.com/teaching/ucsd/147a/lectures/lecture3/10.php

PNP arrow points to wrong direction! — Preceding unsigned comment added by 65.44.170.169 (talk) 14:00, 28 June 2012 (UTC)


 * In the page linked to by 65.44.170.169 and in the Wikipedia article the arrow for a PNP points toward the base, which is correct. A person drawing a schematic is free to position the arrow toward the top of the page, the bottom of the page, or either side, depending on how the circuit is connected. Jc3s5h (talk) 19:33, 28 June 2012 (UTC)


 * Doesn't entirely aid clarity to draw one upside down though, does it.  Spinning Spark  22:55, 28 June 2012 (UTC)

Theory vs application
As someone else stated, there is an extreme amount of "technobabble" and yet very little information on common uses. As I recall from EE, there are at least two ways BJTs are commonly put to use... Let's see some simple circuits, maybe some biasing... emitter-follower vs. amplification... without going into all the molecular details. — Preceding unsigned comment added by 71.197.246.206 (talk) 04:55, 6 July 2012 (UTC)

Outtakes
This inline comment (used twice) are better dealt with here (cut/paste):

Where two of the three "Citation needed" tags are, was this comment: "I believe that Horowitz and Hill have a statement nearly identical to this; someone should verify that and replace this Fact with a ref to HH." Widefox (talk) 12:45, 28 July 2012 (UTC)


 * Widefox's request makes no sense out of context. Please provide text we can search on to find the spot in the article. Jc3s5h (talk) 12:49, 28 July 2012 (UTC)
 * Clarified above. Here's a diff as well Widefox (talk) 13:47, 28 July 2012 (UTC)


 * I fixed the passage. Jc3s5h (talk) 21:53, 28 July 2012 (UTC)

Diodes
''An NPN[clarification needed] transistor can be considered as two diodes with a shared anode. '' Our proverbial bright 12-year-old reader is going to say "Hey, I can make a transistor with these two diodes I found" and when she wires it up and tries it, she's going to be disappointed. This needs to be explained better - two back to back junctions, yes, but not just "diodes". --Wtshymanski (talk) 18:15, 1 August 2012 (UTC)


 * I did some edits to make it more sensible. Please comment or fix it better.  That mess was from an unnoticed IP addition of May 4, 2012.  Dicklyon (talk) 22:47, 1 August 2012 (UTC)

Point contact transistors
To clarify some confusion arising in recent edits, the operation of point-contact transistors requires minority carrier injection.  Spinning Spark  21:11, 22 October 2012 (UTC)

Voltage Controlled Bipolar Transistor
I have added text as the fundamental operation of the bipolar transistor.

Before my edits are considered to be reverted, please refer to the original Gummel–Poon_model paper cited at

http://en.wikipedia.org/wiki/Gummel%E2%80%93Poon_model

A direct quote from this Gummel-Pool paper is (P.828):

“…The new charge control relation arises from the treatment of the transport equation for the carriers that pass between emitter and collector. Use is made of the fact that recombination has only a very small effect on the junction-voltage dependence of the current passing from emitter to collector (later called the dominant current component). Hence for this dependence, but of course not for the base current, recombination is neglected. A direct closed-form solution of the transport equation from inside the emitter to inside the collector is possible…”

It is noted that recombination *is* the base current. Since this base current is neglected (initially) in the Gummel–Poon method of calculating the collector current from the base emitter voltage and collector voltage it is simply not reasonable to then claim that “the collector current is *controlled* by the base current”.

The “charge control” model, by design, as shown above, calculates the base charge resulting from the applied *voltages* at the base and collector. It is noted that the base charge is not the charge flowing out of the base, but the charge in the base region, which has no direct relation to the charge flowing out of the base.

So, fundamentally the bipolar transistor is a voltage controlled device. Any base current that flows is simply a nuisance, and not any way key to transistor operation. This is clearly the opinion of some of the most noted experts (Gummel-Pool) on transistor theory.

If any editor has a more academic *reliable* source that contradicts the Gummel-Pool voltage controlled view above, and can present the basics of an actual theory as to why the bipolar transistor would be base current controlled, present it here, or please leave my latest edits alone. Kevin aylward (talk) 13:29, 27 December 2012 (UTC)


 * Gummel-Pool is just a model, not a physical explanation.


 * I agree, but it is a model based on actual device physics. A detailed model based on base current controlling the collector current that is accurate does not exist.


 * If you know of one, please provide a physics based model that calculates collecter current from knowing base current.


 * The statement that was added, "It should be stressed that there is essentially, no direct physically casual relation between collector/emitter current and base current", is just wrong.


 * No it is not. My statment is correct, and validated by gummel-poon. Did you actually read the Gummel-Pool paper?

“…recombination has only a very small effect on the on the junction-voltage dependence of the current passing from emitter to collector…”


 * Please explain why you do not accept that this reference states two positions. One, that the collector current is dependant on the junction voltages, two, that the base current has a negligible effect, hence its not the base current that controls the collector current!!!


 * In what way do you suggest that the charge sent into the base from the base terminal actually incites charge to flow from the emitter to collector?


 * The charge-control point of view depends, obviously, on charge, which is the integral of net current. If the base lead is cut so no current flows, the transistor doesn't work. Reverted. Jc3s5h (talk) 14:17, 27 December 2012 (UTC)


 * Sure, cut the base lead and no voltage is applied to the base-emmiter junction.


 * You misunderstand what “charge control model” actual means. You need to go and read and UNDERSTAND the GP paper.

“Charge control model” means to calculate the charge in the base region due to the terminal voltages. The charge in the base region is not the charge comming/going from the base lead. The charge in the base is much, much larger in the base region than that supplied by the base terminal. There is also no direct relation between the charge supplied by the base terminal and the charge supplied by the emitter. Go and read the paper! — Preceding unsigned comment added by Kevin aylward (talk • contribs) 16:42, 28 December 2012 (UTC)


 * Before the edit war heats up, there can be more than one description. I hesitate to say explanation; there are no explanations in science.  There are only theories and models and predictions.  What suffices as an explanation is just a retelling of the story in terms of some other theory. In my reading from where I don't remember the best model for the specialist is the charge controlled model.


 * I agree, for example there are two contradictory theories that have identical equations as that of Special Relativity. The second is the Lorenz Ether theory. It is impossible to distinguish them apart experimentally. However, both models agree with experiment. In the case here, there are no base controls the collector current theories that agrees accurately with experiment.


 * I am an analog design specialist.
 * Kevin aylward (talk) 16:34, 28 December 2012 (UTC)


 * That charge can be held on the base by a voltage source or by squirting the current into base until it charges up to the necessary voltage. It comes down to which model is most appropriate for a situation.  The voltage controlled model is non-linear but accurate.  The charge controlled model is sort of linear (beta changes with collector current) but can easily be in error by more than a factor of three.  In an RF design where the driving stage is low impedance, it makes more sense to think of the bipolar transistor as a voltage controlled source.  For small signal work, gm vs. collector current is so repeatable across multiple devices that the manufacturers don't even bother to specify it.  If the driving circuit is high impedance and low frequency  the current controlled model can be useful, as long as one remembers to consider the full range of beta variation.

You appear to misunderstand what Gummel-Poon "charge controlled model" actually is. Read the paper I cite. The GP model, by design, is a model that, yes, calculates collector current from base charge, but calculates the base charge from terminal voltages. It is not a “apply a charge entered from the base terminal and calculate collector current” model. This is immediately clear from the 1st page text., and the paragraph I cite. The paper makes it quite clear that recombination, i.e. base current, has only a secondary effect. Kevin aylward (talk) 11:52, 30 December 2012 (UTC)
 * Yes, it may be true that we have only models of reality in the grand big scheme of things. I agree with the general principle of what you are trying to say here. However, this is not appropriate here. This is about the general, accepted descriptions as to how bipolar transistors actually work from accepted device physics. That is, a transistor works by modifying the potential barriers of the base-emitter junction and collector base junctions. Base current is only incidental to transistor operation. This is truly the way it is. I urge you to read any good book on semi-conductor physics to gain this knowledge.


 * Both points of view belong in the article. But the first model presented should be for the non-specialist.  Right now, in my opinion, neither point of view has been presented in satisfactorily to claim the right of first description.


 * What is the basis for your opinion? Have you taken a first course in semi-conductor physics? Do you have any formal graduate qualifications that indicate that your opinion is valid? Are you a professional bipolar IC designer?


 * This is an encyclopaedia. The best model should be the one that is accepted as correct by those qualified to know.


 * I suggest that the paragraph in question start off with " Collector current is approximately β (common-emitter current gain) times the base current" and then explain how the current controlled current source model arises and its limitations on accuracy and then explain the more accurate but non-linear voltage controlled model.Constant314 (talk) 00:59, 28 December 2012 (UTC)


 * This perpetuates the myth that the bipolar transistor is controlled by its base current. It isn’t. Its controlled by its base emitter voltage.

Please do not revert my edits on the correct description of the operation of the bipolar transistor unless you can provide a true physics based explanation as to why the collector current is actually *controlled* by the base current.

Please do not revert my edits unless you can explain why the description I gave as to the current being controlled by the base emitter voltage, as clearly given by the Gummel Poon paper I cited, is false.

The reality is that, the base current controlled description of the transistor is simply an “old wives tale”. It is impossible, in general, to competently design transistor circuits with such a false understanding of transistor operation. The number of carries entering the base terminal does not control the collector/emitter current. It’s that simple.

It is not an “exaggeration” to clearly explain the true voltage controlled nature of the bipolar transistor. It is necessary in order to correct the very common misunderstanding that leads to much effort being wasted in remedial instruction to new junior analog designers that are unable to design correctly due to such misunderstandings. The

If you wish to discuss this further you can email at kevin_removethis@kevinaylward.co.uk, remove the _removethis — Preceding unsigned comment added by Kevin aylward (talk • contribs) 11:22, 28 December 2012 (UTC)

Kevin, I indented some or your responses and one of my own to make it more obvious to which statement the responds regards. This is the convention for talk pages. It is preferred that you put your new comments at the bottom, although I appreciate the convenience of putting the response within the comments to which you are replying, but it is hard to find them all. If you are going to reply this way, please put your new comments between paragraphs instead of inside them where it may change the meaning. I have partially restored my paragraph and moved your inline comments to the end of the next sentence. I have no intention of changing the meaning of your comments. Constant314 (talk) 17:10, 28 December 2012 (UTC)

Kevin, posting within other peoples comments often destroys the indentations. Please put new comments at the end. I know it will require some extra words to make clear just which statement to which you are replying, but it is worth it. If you persist in doing this, please sign each comment so that we can readily see who is making the comment.Constant314 (talk) 17:26, 28 December 2012 (UTC)


 * Kevin aylward :" I am an analog design specialist."
 * Kevin, I believe that you are an expert, but Wikipedia does not accord any deference to experts. Anyone can claim to be an expert, but Wikipedia has no process to vet experts, hence, the comments of an expert such as yourself do not carry any extra weight.


 * Kevin aylward :"Base current is only incidental to transistor operation."
 * Base current is important, especially when beta is low, because it has to come from somewhere.

Yes it can often be very, very important, but this does not mean that the base current controls the emitter current. I noted that the 1st order effect of base current can be calculated from knowing the ib.rbb. voltage drop. Certainly the source has to be able to supply whatever base current is required. Base current can also be the dominant source of noise. Kevin aylward (talk) 11:52, 30 December 2012 (UTC)
 * Kevin aylward :"I urge you to read any good book on semi-conductor physics"
 * I already agree with you that a voltage controlled charge that control the transistor is the best model.


 * Kevin aylward :"What is the basis for your opinion? Have you taken ...semi-conductor physics?"
 * The basis of my opinion is that I am a user of bipolar transistors and I use both models with satisfactory results. Manufacturer's data sheet specify beta.  Numerous college text books on electronics use the current controlled current source model.


 * Kevin aylward : "This is an encyclopedia. The best model should be the one that is accepted as correct by those qualified to know."
 * We have no way of knowing who is qualified to know.

I agree. The assumption here is that I have given what I consider a very good explanation, partly based on citing THE noted source for transistor modelling, as to why base current does not control emitter current. I gave an explanation as to how the base voltage determined the collector current in the same manner as it determines the diode current in a diode. I assume that those competent to debate would understand the relevance of this and go “wow, the same current flows irrespective of whatever base current flows” and have a light bulb come on as to what that actually means. Kevin aylward (talk) 11:52, 30 December 2012 (UTC)
 * Kevin aylward : "provide a true physics based explanation"
 * A physics based explanation is not required. The requirement is usefulness.Constant314 (talk) 18:06, 28 December 2012 (UTC)

I disagree. If it is being claimed that base current physically determines collector current, then there should be a real physics based theory argument that supports such a view. I have referenced papers, by noted physicists, that refute such a view, and gave a simplified description as to why the voltage controlled model is the appropriate one.

Kevin aylward (talk) 11:52, 30 December 2012 (UTC)

My two cents worth
I think you all have good points. We had tried to cover the different viewpoints already, respecting positions argued in a previous round, in the section Bipolar junction transistor. I don't see how changing "controlled" to "operated" in this section is likely to improve anyone's understanding. From the point of view of controlling collector current, using base current as the control makes perfect sense, and this is the conventional way to discuss beta, even if the physical relationship is not "direct", but only via a small difference from the base–emitter current.


 * It does not make sense to many professional transistor level designers, because it is not correct. Kevin aylward (talk) 11:48, 29 December 2012 (UTC)

As to where "It should be stressed that there is essentially, no direct physically casual relation between collector/emitter current and base current", I can see that not everyone is likely to agree.


 * I agree that it is very difficult to get people to see the light that what they believed to be true, is false. As yet, I see no evidence of any actual alleged *physics* that would attempt to explain *why* or *how* the base current induces emitter current. Don’t you see this as a clue? Kevin aylward (talk) 11:48, 29 December 2012 (UTC)

If this needs to be stressed, show us some sources that say it needs to be stressed, or at least some sources that stress it, and we can decide how much weight to give that POV. The current inferences from what Gummel and Poon say are not enough to support this kind of statement.


 * I did, and it does. It was in the GP paper. It was certainly stressed to me in 1980, when I did my university semiconductor physics course. On day one, the professor said (almost) quote “you may believe that the bipolar transistor is base current controlled. This is wrong. It is a voltage controlled device, and this is why…"


 * This was stated with much vigor by the professor.


 * The lecture then proceeded with all the goodies of semiconductor doping, Fermi levels, potential barriers etc. and derived the basic equations.


 * I don’t believe that anyone that has actually done a formal, proper course in semiconductor physics, as related to the operation of a bipolar transistor would make a claim other than that the transistor, is a voltage controlled device. There is no practical theoretical way to deduce the emitter current from knowledge of base current. Transistor operation is based on modifying potential barrier heights. This is all pretty basic stuff. It is easy to verify in any proper university text book. The issue here, is that there are too many unqualified laymen editing Wikki.


 * I am not posting this in ignorance. I know exactly what I am saying and why. I understand that maybe all laymen, and maybe 95% of practising designers may be deluded as to how transistor work. I am trying to correct that delusion. Kevin aylward (talk) 11:48, 29 December 2012 (UTC)

The rest of the new basic operation paragraph seems less controversial, though somewhat redundant and needs styling work (heading case, formulas, sentence starting with "2nd", etc.). Dicklyon (talk) 17:57, 28 December 2012 (UTC)


 * There is nothing controversial about the inherent voltage controlled nature to qualified physicists. I don’t see that section  as redundant as it shows how the known diode equation results in the same emitter current for the transistor, and  hence, how it is the base emitter voltage, not base current, that determines the emitter current. Kevin aylward (talk) 11:48, 29 December 2012 (UTC)

Kevin, your "Basic Operation" section also appears to be a copyvio from your web article. If you wrote that first, you'll need to state an appropriate license on it to be able to copy from it into WP; or if you wrote it in WP first, you should credit WP for that part.


 * You are welcome to your opinion. I wrote some of the material for WP first and some for my web site first. There is no reason to credit WP or write a licence, as I wrote all of it, apart from any quotes, and give permission here for its use. Kevin aylward (talk) 11:48, 29 December 2012 (UTC)


 * But your web page is claiming licensing terms incompatible with WP's ("This paper may be reproduced so long as no charge is made and that the paper is reproduced in full with full credit given to it's author).

What I personally post to wikki has nothing to do with any licence on my independent web site. If I post anything to wikki, its free to all. Kevin aylward (talk) 11:23, 30 December 2012 (UTC)


 * We are not reproducing it in full in WP, and could not if we wanted to, since we only allow things without derivative-works restrictions. You need to make it clear what the actual license is, or we have to remove it from WP.  Not a big deal, though, as we're probably removing it anyway. Dicklyon (talk) 18:59, 29 December 2012 (UTC)

…err…ahmm… what do you mean by “We”. You are not wikki, and have no authority over as what gets posted. You are welcome to your opinions though. Kevin aylward (talk) 11:23, 30 December 2012 (UTC)


 * In either case, linking it in WP as if it's an authoritative source is not a good idea, as it's really just an unpublished opinion piece. In general, such analyses attempting to say that a common viewpoint is a "myth" are not welcome in WP unless from a WP:Reliable source, and even then must not be given undue weight.  Dicklyon (talk) 18:49, 28 December 2012 (UTC)

I did not refer to my wep page as an authority. I simply added a link to the external links page. I do not refer to it in any of my wikki edit texts at all. Kevin aylward (talk) 11:23, 30 December 2012 (UTC)


 * It is not my opinion, I am simply reformatting in layman’s language, the trivially obvious conclusions from the Gummel-Poon paper, as one example qualified source. It is just very, very, unfortunate that they are so few here that are qualified to actually understand that that is what that paper is stating. GP are THE noted experts on this. They state that the “…recombination has only a very small effect on the junction-voltage dependence of the current passing from emitter to collector…” Anyone that does not actually understand the implications of this statement, and the rest of their paper, should not be attempting to mediate my edits. Kevin aylward (talk) 11:48, 29 December 2012 (UTC)


 * Kevin, you and your professor are free to hold and espouse that opinion, but it's not really well founded.

Says who? My professor had a PhD in physics, you don’t I understand, so it is your opinion that is suspect.

What I state, the professor states, and all relevant physics theory text books states, is very well founded indeed, unfortunately it appears you have missed the basic point I have been making, and missed reading those text books, and missed understanding standard semiconductor theory. Kevin aylward (talk) 11:23, 30 December 2012 (UTC)


 * The notion of causality there is pretty weak. What causes the increased voltage between emitter and base?  The only way to get that increased voltage is to push more current through the junction.  That is, the device physics constrains the relationships between the voltages and the currents, via some dynamics involving the minority-carrier charge stored in the base.  It really makes no sense to call one variable the cause and another the effect.  Consider the lowly resistor and Ohm's law:  of voltage and current, which is the cause, and which the effect?  Neither.  Dicklyon (talk) 18:59, 29 December 2012 (UTC)

Listen up to what I am *actually* saying. I have no fundamental issue with what you write above. In principal, I *agree*. However, it does not address the basic point that I have been making. Sure, it could be (poorly) argued that the current forced into a diode controls the voltage across it, therefore the diode voltage may be argued (poorly) that it is “caused” by the *emitter* *current*. I am not denying this possible (poor) interpretation. What I am denying is that it is the *base* current that *controls* either the diode voltage or diode current. The base current is *not* the emitter current. The base current does not *control* the diode current or the diode voltage. It just flaps in the wind.

Do you deny that, to first order, the emitter current is given by:

IE=Io.exp(q.Vbe/KT)

And that, for reasonable values of hfe, IC=IE.

If you don’t, this discussion is over.

Now, where is the base current term in this 1st order model?

Conclusion?

This is so trivially simple, it’s unreal that, once its been pointed out, that there can be any confusion. Listen up again.

Consider a transistor with its collector open circuit. Apply a voltage to its base emitter. A current will flow in accord with IE=Io.exp(q.Vbe/KT), with all of the diode current now going through the *base* terminal. Now connect a voltage to the collector. Essentially, for the same voltage on the base, the *same* current will flow in the emitter, however, with the collector now sucking up the bulk of the emitter current, the base current now becomes much reduced. So, the emitter current is, essentially, *independent* of whatever base current flows, therefore to claim that the value of base current controls the emitter current is simply absurd. This is how the transistor works. Carriers are injected into the base region from the emitter by applying a voltage at the base emitter junction, and get sucked up by the collector voltage. It’s that simple.

Seriously, what part of “…recombination has only a very small effect…” in the GP paper have you still not understood?

If it were true that base current was important in *fundamental* transistor operation, the GP model would be false, because it is based on that assumption, hence all Spice programs would fail to agree with reality. They don’t. I make my living on knowning that the 50k analog transistor ICs I design, work first time, correctly. It would be very expensive if they didn’t. Money is the final arbitrator in this real universe.

Instead of just making denials to what I post, produce an argument that refutes the logic that I have presented here. Present an argument that actually shows how or why that the emitter current is *controlled* by the base current.

Kevin aylward (talk) 11:23, 30 December 2012 (UTC)
 * This article already has a brief section on the Gummel–Poon model and even acknowledges the GP is more detailed and predicts non-linearity that EB misses and it has a link to the Gummel–Poon article, which needs a lot of work; it's barely more than a stub. I suggest that Kevin work on the Gummel–Poon article where there is very little be changed, deleted and fought over.  Of course the rules still apply about reliable sources, etc.  I think the GP section of this article is sufficient for this article.  However, I don't there would be any objection if the GP section of this article were expanded with statements such as the GP model is based on solid state physics, does a much better job with large signal behavior, uses Vbe as the control signal and is the model of choice for SPICE, but avoids saying everything else is wrong.Constant314 (talk) 01:51, 30 December 2012 (UTC)

Kevin aylward (talk) 11:23, 30 December 2012 (UTC) In principal, I agree with most of what you say here, except for not highlighting that anything is wrong. As noted above, if it were true that base current physically controls emitter/collector current, then it would appear in the first order equations.
 * Kevin, please stop interleaving your comments inside the existing discussion, you are making it very difficulty to follow. Or where it is really essential to do so, at least learn how to INDENT properly.  Spinning  Spark  12:05, 30 December 2012 (UTC)


 * Kevin, I've just looked again at the G-P paper in the Bell System Technical Journal at  http://www.alcatel-lucent.com/bstj/vol49-1970/articles/bstj49-5-827.pdf  I did not see any mention of the Schrödinger equation.  I did not see any QED.  In short, I did not see any fundamental physics.  The closest statement about physics was just before equation 10 where article states "The new charge control relation, derived from basic physical considerations ...".  Based on the BSTJ article,  G-P is just another model.


 * Also, I did not see anywhere within the article a statement that "stressed that there is essentially, no direct physically casual relation between collector/emitter current and base current". Maybe I missed it.  Perhaps you can tell us which page and paragraph and maybe even the sentence or two that stresses no direct physically casual relation between collector/emitter current and base current.


 * Kevin said: "What I personally post to wikki has nothing to do with any licence on my independent web site"
 * Wikipedia's policies for using copyrighted or restricted material are designed to protect Wikipedia from copyright infringement. You have to do it their way, or it will be deleted.  If you care about getting your message out, then get the required licensing statement on your web site.


 * Wikipedia policy takes an inclusive stance with regard to differing points of view. No matter how right the  G-P model is, no matter how much better it is, as long as there is a sufficient group of editors who believe that the current controlled current source (CCCS) model should be expounded in the article, then you won't be allowed to delete it and you won't be allowed to say that it is wrong.  But you can extol the virtues of the  G-P model, as long as you don't disparage the other opinions while doing so.


 * It is not enough that you "referenced papers, by noted physicists, that refute such a view". You are trying to change the majority opinion.  The onus is on you to pull out the relevant sentence or two and tell us exactly where to find it in the reliable source.


 * You "gave an explanation as to how the base voltage determined the collector current".
 * That's great and deserves to be assessable to this article, preferably on the G-P page.  But you haven't given any reliable source that states the that the CCCS model or the E-M model are so egregiously wrong that the very mention of them should be suppressed.


 * I know this is anathema to you, but, if there are "trivially obvious conclusions from the Gummel-Poon paper" you still cannot put them in the article unless you have a reliable source that states those conclusions.


 * You "did not refer to my wep page as an authority". The operating rule here is that if the material would not be acceptable written directly into the article then it is also not acceptable if you write it on a web page and post a link to it.


 * What you say your professor said is hear-say and is not a reliable source.


 * "We" is the collective group of Wikipedia editors and admins. It even includes you.  There are standards and policies that are enforced by the editors and if necessary by the admins.  Wikipedia is not usenet. Constant314 (talk) 15:44, 30 December 2012 (UTC)


 * I have to take issue with your statement "as long as there is a sufficient group of editors who believe that the...model should be expounded in the article, then you won't be allowed to delete it and you won't be allowed to say that it is wrong". While a group of Wikipedia editors might present an obstacle, that is not what should be driving us here.  Kevin certainly should be allowed to delete material or claim it to be wrong if that is the mainstream opinion of reliable sources.  We would do best to concentrate here on what the opinion of RS are rather than the opinion of Wikipedia editors.  Spinning  Spark  17:43, 30 December 2012 (UTC)
 * I understand that a preponderance of credible, authoritative, reliable sources takes precedence over the opinion of the majority.Constant314 (talk) 19:06, 5 January 2013 (UTC)

Kevin, in response to your comments above, at and around "for reasonable values of hfe, IC=IE", let me clarify that I am not trying to say that base current is the cause of emitter current or collector current. I have argued that the notion of causality here is pretty weak; silly even. You are saying it's an error to say the base current "controls" the collector current; I disagree, as this is a common and useful model, whether or not it's directly physical. As for the approximation IC=IE, I'd call that zero-order. The first-order model includes the alpha (or beta/(1+beta)) factor, and explains how base current can control collector current. The fact that many books teach this approach is not an error to be fixed in wikipedia; it's just how it is. Dicklyon (talk) 17:56, 30 December 2012 (UTC)

Voltage Control, Current Control
I've reconsidered the best way to bring this into the article. I think it would be natural to first give the equations for collector current and base current as a function of voltage and then divide the former by the latter. Both currents will have an exponential which will sort of divide out, leaving an equation that collector current is sort of proportional to base current with the proportionality is a function of collector current.Constant314 (talk) 16:14, 2 February 2013 (UTC)

Seems like the hard way to show that the dependence is on base current. Do some people have an easier time considering voltages than currents? In most cases, a base resistor is used, such that you don't need to consider the base voltage. Gah4 (talk) 06:47, 26 April 2015 (UTC)

Unreadable derivation
I have removed the following from the article; {{Quotation|

Current–voltage characteristics
The expressions are derived for a PNP transistor. For an NPN transitors n has to be replaced by p, and p has to be replaced by n in all expressions below. The following assumptions are involved when deriving ideal current-voltage characteristics of the BJT


 * Low level injection
 * Uniform doping in each region with abrupt junctions
 * One-dimensional current
 * Negligible recombination-generation in space charge regions
 * Negligible electric fields outside of space charge regions.

It is important to characterize the minority diffusion currents induced by injection of carriers.

With regard to pn-junction diode, a key relation is the diffusion equation.


 * $$\frac{d^2 \Delta p_{\text{B}} (x)}{dx^2} = \frac{\Delta p_{\text{B}} (x)}{L_{\text{B}}^2}$$

A solution of this equation is below, and two boundary conditions are used to solve and find $$C_1$$ and $$C_2$$.


 * $$\Delta p_{\text{B}} (x) = C_1 e^{x/L_{\text{B}}} + C_2 e^{-x/L_{\text{B}}}$$

The following equations apply to the emitter and collector region, respectively, and the origins $$0$$, $$0'$$, and $$0''$$ apply to the base, collector, and emitter.


 * $$\Delta n_{\text{B}} (x) = A_1 e^{x/L_{\text{B}}} + A_2 e^{-x''/L_{\text{B}}}$$


 * $$\Delta n_{\text{c}} (x') = B_1 e^{x'/L_{\text{B}}} + B_2 e^{-x'/L_{\text{B}}}$$

A boundary condition of the emitter is below:


 * $$\Delta n_{\text{E}} (0'') = n_{\text{E}O} ( \exp (q V_{\text{EB}} / kT) - 1)\;$$

The values of the constants $$A_1$$ and $$B_1$$ are zero due to the following conditions of the emitter and collector regions as $$x'' \rightarrow 0$$ and $$x' \rightarrow 0$$.


 * $$\Delta n_{\text{E}} (x'') \rightarrow 0$$


 * $$\Delta n_{\text{c}} (x') \rightarrow 0$$

Because $$A_1 = B_1 = 0$$, the values of $$\Delta n_{\text{E}} (0'')$$ and $$\Delta n_{\text{c}} (0')$$ are $$A_2$$ and $$B_2$$, respectively.


 * $$\Delta n_{\text{E}} (x) = n_{\text{E}0} (\exp (q V_{\text{EB}} / kT) - 1) \exp(-x/L_{\text{E}})\;$$


 * $$\Delta n_{\text{C}} (x') = n_{\text{C}0} (\exp (q V_{\text{CB}} / kT) - 1) \exp(-x'/L_{\text{C}})\;$$

Expressions of $$I_{\text{E}n}$$ and $$I_{\text{C}n}$$ can be evaluated.


 * $$I_{\text{E}n} = - q A D_{\text{E}} \frac{d \Delta_{\text{E}} (x)}{dx} |_{x=0''}$$


 * $$I_{\text{C}n} = -q A \frac{D_{\text{C}}}{L_{\text{C}}} n_{\text{C}0} ( \exp ( q V_{\text{CB}} / kT) - 1)$$

Because insignificant recombination occurs, the second derivative of $$\Delta p_{\text{B}} (x)$$ is zero. There is therefore a linear relationship between excess hole density and $$x$$.


 * $$\Delta p_{\text{B}} (x) = D_1 x + D_2\;$$

The following are boundary conditions of $$\Delta p_{\text{B}}$$.


 * $$\Delta p_{\text{B}} (0) = D_2\;$$


 * $$\Delta p_{\text{B}} (W) = D_1 W + \Delta p_{\text{B}} (0)\;$$

with W the base width. Substitute into the above linear relation.


 * $$\Delta p_{\text{B}} (x) = - \left ( \frac{ \Delta p_{\text{B}} (0) - \Delta p_{\text{B}} (W) }{W} \right ) x + \Delta p_{\text{B}} (0)$$.

With this result, derive value of $$I_{\text{E}p}$$.


 * $$I_{\text{E}p} (0) = - q A D_{\text{B}} \frac{d \Delta p_{\text{B}}}{dx}|_{x=0}$$


 * $$I_{\text{E}p} (0) = \frac{q A D_{\text{B}}}{W} \left ( \Delta p_{\text{B}} (0) - \Delta p_{\text{B}} (W) \right )$$

Use the expressions of $$I_{\text{E}p}$$, $$I_{\text{E}n}$$, $$\Delta p_{\text{B}}(0)$$, and $$\Delta p_{\text{B}}(W)$$ to develop an expression of the emitter current.


 * $$\Delta p_{\text{B}}(W) = p_{\text{B}0} \exp ( q V_{\text{CB}}/kT)\;$$


 * $$\Delta p_{\text{B}}(0) = p_{\text{B}0} \exp ( q V_{\text{EB}}/kT))\;$$


 * $$I_{\text{E}} = qA \left ( \left ( \frac{D_{\text{E}} n_{\text{E}0}}{L_{\text{E}}} + \frac{D_{\text{B}} p_{\text{B}0}}{W} \right ) \left ( \exp \left ( \frac{q V_{\text{EB}}}{kT} \right ) - 1 \right ) - \left ( \frac{D_{\text{B}}}{W} p_{\text{B}0} \right ) \left ( \exp \left ( \frac {q V_{\text{CB}}}{k T} \right ) - 1 \right ) \right )$$

Similarly, an expression of the collector current is derived.


 * $$I_{\text{C}p} (W) = I_{\text{E}p} (0)\;$$


 * $$I_{\text{C}} = I_{\text{C}p} (W) + I_{\text{C}n} (0')\;$$


 * $$I_{\text{C}} = q A \left ( \left ( \frac{D_{\text{B}}}{W} p_{\text{B}0} \right ) ( \exp (q V_{\text{EB}} / kT ) -1 ) - \left ( \frac{ D_{\text{C}} n_{\text{C}0} }{ L_{\text{C}} } + \frac{ D_{\text{B}} p_{\text{B}0} }{ W } \right ) ( \exp (q V_{\text{CB}} / kT ) -1 ) \right )$$

An expression of the base current is found with the previous results.


 * $$I_{\text{B}} = I_{\text{E}} - I_{\text{C}}\;$$


 * $$I_{\text{B}} = q A \left ( \frac{D_{\text{E}}}{L_{\text{E}}} n_{\text{E}0} ( \exp ( q V_{\text{EB}} / kT ) - 1) + \frac{D_{\text{C}}}{L_{\text{C}}} n_{\text{C}0} ( \exp ( q V_{\text{CB}} / k T ) - 1 ) \right )$$

}}

My original intention was to move it the Early effect article since, without looking at it too carefully it seemed to belong there because it was inserted in the base-width modulation section. However, on a second look it seems to be a derivation of Ebers-Moll. However, without explanation (of at least the symbols used) it is perfectly useless in the article and is likely to discourage a large number of readers.  Spinning Spark  09:03, 8 April 2013 (UTC)

Voltage controlled model redux
I just removed the following from the article: "The above discussion described BJTs as current-controlled devices (constant β), however in theoretical discussions it would be more accurate to say that they are voltage-controlled. For an NPN transistor, the voltage applied to the base draws electrons out from the emitter, however these electrons end up being pulled into the collector instead. The fact that a small base current is needed is simply a consequence of practical factors like recombination and base holes entering the emitter. Ideally a bipolar transistor could be made without these effects, so that no base current would be required for operation (infinite β). The fact that the parameter β is constant over a wide range of operating parameters (only true in some transistors) is a consequence of the exponential growth of both base and collector currents."

It was inserted at the start of the Ebers-Moll section, but does not seem to be relevant to Ebers-Moll (unless it was intended as a criticism of it). This seems to be a resurrection of the voltage-controlled argument discussed ad nauseum above. By all means lets have a voltage-controlled model in the article, but it needs to be properly explained in a section of its own, and it needs to be properly cited to a reliable source.  Spinning Spark  10:50, 22 June 2013 (UTC)

hfe
I've just created hfe as a redirect to Bipolar_junction_transistor. It's the best link target I could see to hand, but we have a pretty obvious need for an entry-level article on hfe. Anyone fancy writing a decent explanation? Andy Dingley (talk) 11:18, 24 November 2013 (UTC)

Missleading language in the previous phrasing
I thought I'd leave a few lines in the talk page since my edit in the previous version 'introduced misleading language, and if misleading bits were clarified, the lead would become as long as the whole article'.


 * "By design, most of the BJT collector current is due to the flow of charges injected from a high-concentration emitter into the base where there are minority carriers that diffuse toward the collector..."
 * Injected charges are (i.e. become) the minority charge carriers in the base. It is not like "well, charges are injected from emitter to base, and then there are also minority charge carriers in the base region and they diffuse toward collector". There are indeed thermally generated electron-hole pairs in the depletion region (which are majorly recombined after generation, and the small remaining portion leads to a reverse current) but this sentence is (should be) talking about injected charge carriers. Also, as a digression, misleading language is much better than misleading information I think; it's statistics (probably not Boltzmann though).


 * "By design..."
 * What's special about BJT design is not that collector current is due to flow of charges from emitter to collector. What's special about BJT design is that;

  Three layers are properly doped (i.e. Nemitter > Nbase ~ Ncollector) so that diffusion from emitter will be an optimally effective mechanism in the conduction. Base layer is kept relatively narrow so that the heavily doped emitter region causes the emitter-base junction to span over almost all of the base region leaving very little neutral (doped) region for annihilation of charge carriers as a result of electron-hole recombination. So, by design, a relatively small current compared to that of emitter's and collector's goes through base (like walking on water).  


 * Here is what happens in active mode (in which BJT is used for amplification purposes rather than switching) step by step:
 * Forward biased emitter-base junction contracts (compared to equilibrium width). Since emitter is heavily doped compared to base, most of the width of emitter-base junction still lies on the base side.
 * Majority charge carriers of emitter region are injected into base region where they are minority charge carriers (rather than majority charge carriers).
 * Since base region is relatively narrow (and therefore, width of the neutral region outside the depletion zone is relatively narrow as well), and since majority charge carrier concentration in base is relatively small, diffusion rate is much larger than recombination (~annihilation) rate. Therefore, most of the emitter current is swept through base-collector junction.
 * Reverse biased base-collector junction expands (compared to equilibrium width). This means the electric field within the depletion region remains, and indeed gets stronger, in the direction of flow, not against it. Therefore, charge carriers in the base-emitter region drift through neutral region in collector. And finally, from the neutral region of collector, they continue toward the attractive terminal of the voltage source.


 * Apart from the particular design details given above, the law of the junction explains how the above design is used for amplification purposes:


 * $$ c_{biased} = c_{equilibrium} ~ \text{exp} \left ( \frac{eV}{kT} \right )$$


 * ,where cbiased and cequilibrium are biased and equilibrium concentrations of minority charge carriers at the end of depletion zone in the region to which carriers are injected, e is elementary charge, V is applied voltage, k is Boltzmann constant, and T is absolute temperature. Note that a higher cbiased implies a higher BJT collector current.


 * Since any change in emitter-base voltage changes the diffusion through base region (and thus in collector current) exponentially, a BJT can be used for amplification purposes.


 * 'Since the central fundamental concept in BJTs' working is minority carrier injection, these devices are classified as minority-carrier devices.'
 * I think it is important to mention the widely referred working principle (minority carrier injection) of any semiconductor device whose operation relies on carrier motion through junctions.


 * A note about the terms anode and cathode
 * Electrical engineers (and Wikipedia) define the anode, for all circuit elements (including batteries), as the terminal to which positive (conventional) flow enters, or equivalently, the terminal from which the negative (electron) flow departs. This definition is intuitive for batteries: Anode of a battery is where the oxidation reaction occurs, which produces electrons and therefore makes the terminal negatively charged, and thus a battery’s anode is where the positive (conventional) flow enters. However, when the term anode is used for other polarized circuit elements such as diodes, the connection of these elements to a battery circuit becomes non-intuitive: anode of the diode is connected to cathode of the battery, and cathode of the diode is connected to anode of the battery (just like connecting two batteries in series; anode to cathode, and cathode to anode). Also note that, in order for a diode to conduct electricity, the p-type semiconductor end must be connected to the positive terminal of the battery, and the n-type end must be connected to the negative terminal of the battery, so that holes and electrons are repelled by the terminals and can overcome the electric field in the depletion region. Therefore, according to definition of the term anode, p-type end of a diode is called anode. However, majority charge carriers in the p-type end of a diode are positive charged (i.e. hole), and calling it anode is non-intuitive.


 * Due to these inconsistencies, it is better to avoid using terms “anode” and “cathode” unless the discussion is confined to electrochemistry (e.g. batteries), and in general it is always better to refer to terminals of a diode as p-type and n-type terminals, and terminals of a battery as positive and negative terminals.


 * Apparently there has been a demand for simplification since 2012: "This section may be too technical for most readers to understand. Please help improve this section to make it understandable to non-experts, without removing the technical details. The talk page may contain suggestions. (July 2012)".


 * Anybody who possess the power of non-misleading language and think that it would improve the article is welcome to incorporate any part of this message, as-is or modified, to the article.


 * "...if misleading bits were clarified, the lead would become as long as the whole article."
 * This is interesting.

85.110.21.35 (talk) 19:29, 9 April 2014 (UTC)

The language as of 22:34, 5 April 2014 UTC:

"By design, most of the BJT collector current is due to the flow of charges injected from a high-concentration emitter into the base where there are minority carriers that diffuse toward the collector, and so BJTs are classified as minority-carrier devices."

The language after a series of edits by 85... "By design, collector current is due to flow of charges injected from high-concentration emitter into base as minority carriers which diffuse toward the collector from there; only a small fraction of the current goes through base. Note that there is also a small leakage current in the reverse direction due to thermal generation of electron-hole pairs within the emitter-base depletion layer. Since the central fundamental concept in BJTs working is minority carrier injection, these devices are classified as minority-carrier devices."


 * "[2]" at the end of the section name is a link created with Template:Diff2. Not everybody who use wikipedia knows how to use it, but everybody who use wikipedia knows how to follow links. 85.110.21.35 (talk) 20:46, 9 April 2014 (UTC)

The statement "collector current is due to flow of charges injected from high-concentration emitter into base" is implicitly referring to active mode. Modes exist where this is not true.


 * The statement you've just quoted above was there before I edited, after I edited, and after my edit was 'restored'. It is still there. It's hard to make sense out of your language (I am not saying it is misleading). 85.110.21.35 (talk) 20:46, 9 April 2014 (UTC)

The statement "only a small fraction of the current goes through base" implicitly refers to active mode, and should say that that only a small fraction of the emitter current enters or leaves the transistor through the base contact.

The problem is that it is confusing to make statements in the lead about the active mode when the readers, not having yet read the article, don't know what active mode is. Jc3s5h (talk) 19:48, 9 April 2014 (UTC)


 * Rather than wasting our and probably others' time, I'd trust your wisdom (in wikipedia). good day/night. 85.110.21.35 (talk) 20:46, 9 April 2014 (UTC)

Awful
This is one of the worst wiki pages I've ever seen if you measure by content per word. There are reams and reams of unexplained technical babble that, from this talk page, is not even particularly clear to experts, and leans very heavily on the personal experience (eg, original research) of the authors. And in the end there is not really any discussion at all in laymans terms of what this device does. Technicians will probably be getting these formulas out of a technical reference, so it seems very weird to have that emphasis here when it is not accessible to a layman. The whole point of having any technical information is so an educated layperson from another field can have some deeper insight. There is no utility in formulas and discussions that would have meaning or value only to people who are experts in this field. So the point I'm getting at is, if you were to delete this page and replace it with a 50 word explanation of what a bipolar junction transistor is, with NO technical information at all, it would be a higher quality article. And yes, I do value the technical information in most wiki pages. But this one is a total disaster. 76.105.216.34 (talk) 20:36, 5 July 2014 (UTC)
 * No doubt this article can be greatly improved, but your comment about formulas does not really seem to be justified. There are no really difficult mathematics anywhere in the article and the description of the mathematical modelling of a transistor does not really get underway until well over half-way through the article.  Perhaps you could give an example of what you mean in that respect?  The workings of a BPJT is difficult to understand, even for those with some electrical science skills.  It cannot properly be explained without introducing concepts such as doping, p-n junction and minority carriers, the latter of which has no analogy to help explain it.
 * One of the problems of an encyclopaedia format is that these grounding concepts are explained in separate articles but there is no guarantee that the user will read them first. In fact, they probably won't.  Unlike with a textbook or college course, the reader will dive straight in to the topic they want to know about without first reading, or even knowing about, the basic grounding they need to understand it.  Would you like to help improve this article for a general reader?  If you do, I would be willing to work with you for technical advice. SpinningSpark 07:41, 6 July 2014 (UTC)
 * >>"minority carriers, the latter of which has no analogy to help explain it."
 * I have a feeling that you do not understand what a minority carrier is. A minority carrier can be an electron or a hole according to which type of material, p or n, one is talking about. If you meant to say that there is no analogy for positive charge carriers i.e. holes, you would be wrong.
 * --H.E. Hall (talk) 22:38, 19 August 2014 (UTC)
 * Your feeling would be wrong, I know perfectly well what minority carriers are. What I meant was that one cannot add something to, say, the hydraulic analogy that would represent the action of minority carriers to make it more familiar and easier to understand for a general reader. SpinningSpark</b> 00:02, 20 August 2014 (UTC)

I agree with you, this article is awful, abbreviations and technical terms used without explanation, not enough citations, and I think I know why. I decided I would help and replaced the first paragraph (which was un-cited) with the following two paragraphs (cited), as the first several edits I planned to make. Within a few hours my edits were reverted. I am not going to fight a revert war, too bad for wikipedia. Here is what I wanted to add, you decide if they are not a better introductory paragraph than the current first paragraph:


 * Transistors are three-terminal, semiconductor devices that can control electric current in a manner similar to the way that a faucet controls the flow of water. A control knob controls the flow of water in a faucet. In a bipolar transistor, a small current applied to a control lead (a wire) on the transistor, controls the flow of current through the other two leads on the transistor.


 * Transistors are used in many different kinds of circuits. You can find them in switching circuits, amplifier circuits, power supply circuits, digital logic integrated circuits, and many other kinds of circuits. There are two families of transistors: Bipolar and Field Effect. This article will deal exclusively with bipolar transistors. There are two configurations for bipolar transistors: NPN and PNP.

I was getting ready to add an explanation of NPN, PNP, and how silicon is doped to make P and N type materials. --H.E. Hall (talk) 22:38, 19 August 2014 (UTC)

-


 * Is the "drainpipe analogy" really helpful in explaining this? I'm not sure there's a large contingent of readers who are going to benefit from the hydraulic analogy who are not going to have to quickly abandon it once they have any further interest in the subject. Why introduce a tangential concept in the introduction which has not place in the body of the article?  There's a century of physics to explore here! We don't want to waste the reader's time on a mode of explanation that good textbooks on the subject seem not to require. --Wtshymanski (talk) 13:44, 20 August 2014 (UTC)
 * I agree with Wytshymanski that this kind of talking down to the reader is not useful. Anyone who looks up bipolar junction transistor is likely to at least understand what a junction is.  In the most general articles we should not make assumptions about readers' knowledge, but for increasingly more specialised articles it becomes necessary to assume some background knowledge.
 * However, that's not the reason I reverted you. You have not added an introduction to bipolar junction transistor as you claim.  You have added an introduction to transistor.  It does not belong in this article.  It also does not belong in the lede.  The lede is mean to be a summary of the article.  Adding material that is not in the body of the article is not appropriate.  The lede is also meant to define the topic in the first sentence and bold the title term.  Your addition pushed this sentence down to the third paragraph.  By the way, it is not usually considered necessary to provide citations in the lede for precisely the reason that it is a summary of the (hopefully already cited) body of the article.
 * If you had done this in a one-line stub I would have welcomed you and encouraged you to do more. In a well-developed article (and generally on Wikipedia) you need to take a bit more care and be prepared to work together with others.  Taking the attitude that we can take your contribution as it is or "too bad for wikipedia" is childish and will get you precisely nowhere.  No one will care if you walk off in a huff. <b style="background:#FAFAD2;color:#C08000">Spinning</b><b style="color:#4840A0">Spark</b> 18:26, 20 August 2014 (UTC)

Anchor duplicates Ebers–Moll heading
When you link to Bipolar junction transistor, the article actually has two places with the same identifier to jump to. It means the generated HTML page is technically invalid; see the second point under Template:Anchor, or ~dispenser/cgi-bin/rdcheck.py/Bipolar junction transistor for instance. There is no difference in the dash used (an en dash) between the heading itself and the second Anchor argument. Perhaps my original edit summary wasn’t clear enough, but I hope this clarifies things and you are able to remove the problem anchor again. Vadmium (talk, contribs) 01:46, 29 July 2014 (UTC).
 * I always thought that anchors could be used to protect against heading name changes, but apparently not. <b style="background:#FAFAD2;color:#C08000">Spinning</b><b style="color:#4840A0">Spark</b> 07:59, 29 July 2014 (UTC)

Images used here are Inconsistent
I have issues with these images.

is not wrong but inconsistent with canonical practice when introducing schematic symbols, which is to show transistor symbols rotated to have the emitter or source terminal at the bottom. The NPN symbol is shown properly in this way. The article on "Electronic Symbols" uses this same inverted PNP symbol. Showing an rotated forms of symbols should be done in that article, if it deemed relevant at all.
 * This image of the PNP BJT schematic symbol: BJT_PNP_symbol_(case).svg

is very confusing, and I think, wrong. It shows both conventional (black arrows) and physical (internal) current flows. See "Electric Current: Conventions""[]". Normally only one flow model is applied in explanations. If we are explaining how to design electronic circuits, we use "conventional current flow" (current flows from positive to minus potentials). But explaining the actual physics, as the Diode article does, we should use actual physics and "physical current flow". Since the purpose of this image is to reveal the internal operations of the transistor, we should use only physical current flow throughout.
 * This image of the "NPN BJT with forward-biased E–B junction and reverse-biased B–C junction":


 * Other images ("Structure and use of NPN transistor", "Structure and use of PNP transistor", Ebers-Moll models, and subsequent images) show Conventional current flow (black arrows). As explained above, this only applies to design of electronic circuits. So if the purpose of these parts of the article is to how to use the transistors (i.e. design and model circuits) then conventional current flow is correct, but the switch from one to another within the article should be very clearly explained. Or, perhaps a better choice, move these parts to a new article on "designing with transistors" (The topic of current flow direction is a well-known source of confusion in electronics.).

Rich S 10001 (talk) 15:27, 7 September 2014 (UTC)

As for the symbol, it is usually drawn as most convenient for the circuit in question. For one, consider a push-pull amplifier circuit. As to the diagram, the description is of the physics inside the transistor. Outside, one normally considers conventional current. If you really want to know, you need the band structure of the metals used for wires. Many metals have significant hole bands, with aluminum almost as much hole conduction as electrons. But note that the hole vs. electrons in the metal doesn't affect which carriers go into the semiconductor. Then you need a good explanation of what makes an ohmic contact. Gah4 (talk) 07:04, 26 April 2015 (UTC)

Beta vs Hfe
''The value of this gain for DC signals is referred to as h_{\text{FE}}, and the value of this gain for AC signals is referred to as h_{\text{fe}}. However, when there is no particular frequency range of interest, the symbol \beta is used[citation needed].''

There are different versions between the PNP and NPN active mode descriptions, with one [citation needed] and the other with a citation. It seems to me that β is used in a less formal context, and Hfe when one needs to more exact. One might indicate, in general, the gain of an amplifier without a frequency response graph might be β, but with a graph Hfe, or β without a specific bias, but Hfe once the bias is specified. But is there a reference that explains this detail? Gah4 (talk) 07:16, 26 April 2015 (UTC)
 * hfe arises from the h-parameters and thus has implied test conditions (short-circuit output) from the definition of h-parameters. The test conditions for beta, on the other hand, must be explicitly stated.  Thus, beta can be specified for more realistic operational conditions.  The hfe can be thought of as a specific instance of beta under the given test condition.  The difference has nothing to do with frequency range.  Beta can be specified for DC and small-signal just as well as it can be for hFE/hfe although there is no generally recognised separate symbols for beta for these two cases as far as I know.  Most text books simply treat hfe and beta as synonyms. <b style="background:#FAFAD2;color:#C08000">Spinning</b><b style="color:#4840A0">Spark</b> 12:55, 26 April 2015 (UTC)

Collector current equations
I see this equation under the DC section for the collector current:


 * $$ i_{\text{C}} = I_{\text{S}} \, e^{\frac{v_{\text{BE}}}{V_{\text{T}}}} \left(1 + \frac{V_{\text{CE}}}{V_{\text{A}}}\right)$$

Should the equation be like this instead since it's under the DC section?


 * $$ I_{\text{C}} = I_{\text{S}} \, e^{\frac{V_{\text{BE}}}{V_{\text{T}}}} \left(1 + \frac{V_{\text{CE}}}{V_{\text{A}}}\right)$$

If it should not be then it contradicts these two equations under the Ebers-Moll model:


 * $$I_{\text{E}} = I_{\text{ES}} \left(e^{\frac{V_{\text{BE}}}{V_{\text{T}}}} - 1\right)$$


 * $$I_{\text{C}} = \alpha_F I_{\text{E}}$$

ICE77 (talk) 19:54, 14 October 2015 (UTC)

Introduction
Although this Wikipedia article has some good explanations and illustrations some parts are very technical and way beyond the comprehension of the non expert. That aside though, I suggest that the introduction could be rationalised and better structured to give a more general, simpler, more readable, and more easily understood introduction to the BJT. CPES (talk) 05:49, 19 October 2015 (UTC)

on/in/of the order of
This article had 'on the order of' which I changed to 'in the order of', thinking the original was just a simple error. Here in the UK, I had never come across the 'on' version. Subsequently Glrx reverted it back to 'on' so it was no error. Intrigued, I did a bit of investigating and it turns out there are three versions: 'on the order of', 'in the order of', 'of the order of'. 'on' is used more in the US, while 'in' is common in the UK, but the strictly correct wording as far as I can tell is 'of the order of'. http://english.stackexchange.com/questions/94451/something-is-of-in-the-order-of

That's the great thing about Wikipedia, you always learn something new. CPES (talk) 10:44, 26 October 2015 (UTC)


 * Prepositions are screwy. If you want some fun, choose a random verb and then follow it with a prepostion: pull off, pull out, pull through, pull at, pull behind, ...; tie up, tie down, tie on, .... Glrx (talk) 16:31, 26 October 2015 (UTC)
 * This is less preposition than idiom IMO. Local usage can & does vary a lot, like this case. It can, in some cases, completely change the meaning: in the U.S. & Canada, you'd root for a sport team; in Oz, "root" is slang for sex...  TREKphiler   any time you're ready, Uhura  21:10, 26 October 2015 (UTC)

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Active vs. saturation region
User:Gah4 justifies this edit with the edit summary "In saturation, not so unusual in switching circuits Vbe is about 0.7V, Vce about 0.3V. Go to talk page if you disagree."

The passage in question, before it was changed by an IP editor, stated "That is, when there is a positive potential difference measured from the emitter of an NPN transistor to its base (i.e., when the base is high relative to the emitter) as well as positive potential difference measured from the base to the collector, the transistor becomes active. [emphasis added]"

User:Gah4 wants to retain the version by the IP editor, which changes the last occurence of "base" to "emitter". But the sentence says the transistor is active. This is ordinarily taken to mean the active region, which is different from the saturation region, which User:Gah4 mentions in the edit summary. Jc3s5h (talk) 04:06, 6 December 2016 (UTC)
 * I can't see how it would be correct either way. Why not get a better definition from a source?  As for saturation, it is unfortunately defined in roughly opposite ways in bipolar and MOS devices.   In bipolar NPN, base > collector would be saturation region (roughly); while emitter > collector would mean that emitter and collector have been interchanged; not a region.  Dicklyon (talk) 04:26, 6 December 2016 (UTC)
 * This book says base < collector in active region; opposite of what our article has been saying, and I agree (though it can go slightly the other way and still be active). Dicklyon (talk) 04:33, 6 December 2016 (UTC)
 * I think the problem was just that voltage differences were being described in an unconventional direction, and that with that fixed, Gah4's change makes a lot more sense. See if you agree. Dicklyon (talk) 04:49, 6 December 2016 (UTC)
 * Generally, I'm pretty sure "potential difference measured from A to B" usually is taken to mean V_A - V_B. But is was the other way around here.  If there are sources that do it that way, show me. Dicklyon (talk) 05:03, 6 December 2016 (UTC)
 * OK, first we are talking common emitter configuration. Next, the voltages will all be the other way for PNP vs. NPN, but Vbe and Vce are normally the same sign for active region. There are many definitions here: https://www.quora.com/What-is-saturation-active-region-in-a-transistor but it looks to like any collector current less than saturation is active.  At almost, but not quite saturation, such as Schottky TTL, Vce should still be less than Vbe, but not quite as much. But otherwise, the usual descriptions of common emitter mode are in terms of Vbe and Vce. Gah4 (talk) 06:29, 6 December 2016 (UTC)

Complementary Pairs
Why does this article NOT have a "complementary pair" section? It needs to be added. • Sbmeirow  •  Talk  • 04:53, 26 March 2017 (UTC)


 * Good idea, go for it. Andy Dingley (talk) 08:59, 27 March 2017 (UTC)


 * Yes. Maybe add a little prose saying what makes them complimentary. Constant314 (talk) 11:08, 27 March 2017 (UTC)


 * Comment. There's a slippery slope. The article is about the device rather than how it is used. Should there be a section on devices used in push-pull circuits? How about totem-pole circuits? I think it is reasonable to cover circuits that exploit fundamental properties of a BJT: the applications section includes temperature sensors and logarithm converters &mdash; but those topics are short. The application section on amplifiers is also short, but it doesn't even mention differential pair (it should; very good matches can be made). The complementary transistor topic is more relevant in an amplifier article and a list of complementary devices is too detailed here. Glrx (talk) 16:11, 5 April 2017 (UTC)


 * Comment. Yes, but the fact that reasonably complementary devices can be made is worth indicating.  That is, even with different mobilities and such, that they can be close enough to allow for appropriate circuits.  A link to (I presume it exists) the push-pull amplifier would seem reasonable, without describing it here.  A few representative pairs might be nice, but yes, don't list them all. Gah4 (talk) 21:14, 5 April 2017 (UTC)


 * Comment. The "complementary transistor pair" topic isn't explained anywhere on Wikipedia (but I could be wrong).  I've noticed text in articles using the term "complementary pair", but I couldn't find any wikilinks pointing at an article or section that explains what it means.  This is a reasonable missing topic, thus solve the problem by adding a section to some article or create a new article, I don't care.  Thanks in advance.  •  Sbmeirow  •  Talk  • 05:08, 6 April 2017 (UTC)
 * More specifically, does "complementary pair" have any defined or accepted meaning? It always looked to me like more of a marketing concept, to help you choose a pair of roughly comparable transistors, whether any particular parameters were well matched or not.  And 20th-century books seem to treat it as a generic concept of pairing a PNP with an NPN, not there are there are particular important pairs of part numbers.  Dicklyon (talk) 05:43, 6 April 2017 (UTC)
 * Comment. Complementary transistor pairs occur beyond bipolar junction transistors. Most notably there is CMOS, but see also Discrete complementary JFETS.  I think there is a case for an overview article complementary transistor pair and a case for complementary bipolar junction transistor pair as a separate article.  The latter could include links to the pairs we already have articles on and Sziklai pair as well as specific application circuits. <b style="background:#FAFAD2;color:#C08000">Spinning</b><b style="color:#4840A0">Spark</b> 19:01, 13 February 2018 (UTC)

Injection from the base
File:NPN BJT Basic Operation (Active).svg gives a misleading impression of what is going on. It suggests the minority carrier injection from the base into the emitter is comparable to the injection from the emitter into the base. The base's carrier concentration should be much, much, smaller than the emitter's. Consequently, the injection should be very small (fewer available carriers to get jostled across the junction). Judging by the widths of the arrows, $&beta;=i_{C}/(i_{B1}+i_{B2})=1.25$, which is way too low. My guess is $i_{B1}<<i_{B2}$. Glrx (talk) 00:42, 24 April 2018 (UTC)


 * OK, but there is a limit to the resolution of the picture. It is usual to build them with higher beta, though power transistors are not so high. I remember in an undergraduate lab where we made our own transistors, that mine was greater than one, maybe 1.25. Someone else was less than one, but it still followed the appropriate relation, and so got credit for it. (I suspect that the lab has changed over 40 years.)  You might get the picture up to 2 or 3, but not much more. Gah4 (talk) 02:03, 24 April 2018 (UTC)


 * The 2N3055 has a minimum hFE of 5.0 at 10 amps. Gah4 (talk) 02:15, 24 April 2018 (UTC)


 * Yes, but the 2N3055's $h_{FE}$ at 4 A has the more mundane minimum of 20 (and could go as high as 70). At 10 A, the $V_{CE(sat)}$ is 3 V, so the collector probably isn't doing a good job of collecting with a 4 V $V_{CE}$. And none of those numbers suggests the b-to-e minority injection current will dominate the base recombination current as shown in the pix.


 * I love the $f_{T}$ of 2.5 MHz. The cooling hose came off the laser power supply and sprayed water all over the neighboring optics bench, and then the no-longer-cooled power supply blew up. I'd never seen a hole in a TO-3 case and haven't since. Glrx (talk) 08:12, 24 April 2018 (UTC)

Should this sentence end with voltage-control, or current-control?
I'm trying to follow this sentence (and I DO have an understanding of BJTs). It seems to me it should end with " ... so the current-control view is often preferred." (BUT PLEASE READ MY WHOLE COMMENT)

"The voltage-control model requires an exponential function to be taken into account, but when it is linearized such that the transistor can be modeled as a transconductance, as in the Ebers–Moll model, design for circuits such as differential amplifiers again becomes a mostly linear problem, so the voltage-control view is often preferred."

Even just syntactically/semantically, the sentence starts with discussing the voltage-control model, then has a "but," so it would make sense that the remainder talks about the alternative, the current-controlled model. I suspect whoever wrote this knew what they were trying to say, but accidentally wrote voltage instead of current near the end of the sentence.

But then again, if there's a resistor in series with the base, and this resistor is dropping (say) several volts, then the voltage between the (non-base side of the) resistor and the emitter IS approximately linear to the collector current, and this is a "mostly linear" transconductance. Maybe THAT is what the writer meant, but either way, it's not clear.

On the third hand (and I'm starting to think this is the "real" explanation), the reference to differential amplifiers implies (but does not state!) very low signal levels across Vbe (a few millivolts or less), and such signals ride on a small and "mostly linear" portion of the exponential curve (where, for larger signals, the collector current doubles with approximately every 20mV increase in Vbe), and THIS could be what is meant. Even here it should say a linearized voltage-control view, rather than just voltage-controlled view.

I find the sentence confusing, apparently because it is missing some qualifying information, but rather than just adding such info I hope it would be rewritten for clarity. I've never had to think through a sentence so hard even though it might be technically correct.Benbradley (talk) 05:37, 12 December 2018 (UTC)
 * The sentence should end with voltage control. The control voltage is applied directly to the base in a common emitter configuration.  The output is the collector current.  The "it" that is linearized is the exponential input voltage to collector current curve.Constant314 (talk) 06:10, 12 December 2018 (UTC)


 * I think that in a common-emitter configuration the current-control view would be preferred, since it's linear instead of exponential. But in the differential transconductance amplifier, the voltage-control view is preferred, since the behavior is close enough to linear for small voltage differences (and for larger differences you can a tanh compression, approximately at least). Dicklyon (talk) 06:26, 12 December 2018 (UTC)


 * Current control is linear-ish, with an unpredictable departure from linearity that varies noticeably from device to device. Voltage control is strongly non-linear with a very predictable  curve that is strongly matched from device to device.  In the diff amp, device matching is far more important than linearity.  With regard to the common emitter stage, in my own work, it depends on the nature of the source that is driving the stage.  If the driver is high impedance, then I use current control.  If it is low impedance, I use voltage control.  At high frequency, due to the Miller capacitance, common emitter stages have a low output impedance and hence look like voltage sources.  So, a first CE stage is ready to drive a second CE stage with voltage control of the second stage.Constant314 (talk) 19:20, 12 December 2018 (UTC)


 * I think the sentence is referring to a small-signal analysis, where all nonlinearities are appproximated as linear. In a small-signal analysis a voltage control model would not have the difficulties it would have in a large signal analysis. Jc3s5h (talk) 12:36, 12 December 2018 (UTC)

reverse active mode
The article indicates that reverse active mode is seldom used. In most types of circuits, I expect that is true, but it is an important part of the operation of TTL circuits. Specifically, the advantage of TTL over DTL. As TTL is getting less common, and CMOS more, I suppose it is less common than it used to be, but still not so seldom. Gah4 (talk) 07:54, 29 March 2020 (UTC)

Why is there a random formula for $$J_n(\text{base})$$
This formula in the Ebers Moll model section comes out of nowhere. $$J_n(\text{base})$$ doesn't appear in any formula and nothing explains what base internal current is. I can't fix it because I do not know.

$$J_{n\,(\text{base})} = \frac{1}{W} q D_n n_{bo} e^{\frac{V_\text{EB}}{V_\text{T}}}$$

2600:8807:5480:713:EC68:B0E5:991B:BFAC (talk) 00:05, 25 May 2020 (UTC)

Propose removal of "Technical" tag (on section "Function") dating from 2012
The "Technical" tag on this section of the BJT article does not seem to apply any longer; for example, many inline citations now exist, leading directly to Wikipedia articles that explain the concepts involved. I have read the section and do not see the need for this tag at this date; also, the Talk page does not contain much discussion of this issue, and certainly nothing that can be decribed as "active".

As the BJT is a complex system, there will be a need to use technical terminology in explaining it. This is no different from any other advanced/non-introductory concept and does not (in my opinion) warrant a tag "in-and-of itself". I do believe a few tweaks/improvements can still be made (and am happy to make them), however I believe the "Technical" tag has served its purpose in the last decade and is no longer needed.

I am raising the issue here to see if anyone has strong feelings about this, and also if anyone is willing to help with improvements. Snooze Dogg (talk) 12:34, 27 July 2022 (UTC)
 * Removing the tag is much easier than fixing the article. But have we really done all we can to make the presentation more accessible, or is it infested with relativistic effects, excess math typesetting, and spurious ISO standards? --Wtshymanski (talk) 02:20, 14 August 2022 (UTC)
 * I vote for removing it. Removing it doesn't say that the article is perfect, as no article ever is. With cn, we usually know we can remove it when we supply a (hopefully good enough) citation. In this case, the line is fuzzier. There is no completely untechnical explanation of a bipolar transistor. (There might almost be for a MOSFET.) If the article is within the range of the usual article on a technical subject, I think we can remove it. Gah4 (talk) 12:14, 15 August 2022 (UTC)