Talk:Miller effect/Archive 1

Untitled 2006 post
Discovered effect in 1924 when working with transistors? Transistors were not invented for another 20 years...

The German Wikipedia says that it was discovered in 1924 by a Man from Poland named Nehpets Miller....

I believe the formula should be more like (1 + A)C        cheet 22:29, 13 December 2006 (UTC)

Picture needed
A picture showing how the impedance is connected to the amplifier helps.
 * Added one. Roger 16:16, 2 May 2007 (UTC)

Confusion between voltage gain and magnitude of voltage gain?
In the introduction to the article and in the Derivation section, reference is made to the Miller effect multiplying the capacitance by a factor of (1+AV).

However, in the Notes section is a statement that AV is a negative number for most amplifiers.

Taking this statement and the earlier statement that the capacitance is multiplied by a factor of (1+AV) literally would seem to imply that the capacitance is reduced for small Av (between 0 and -1), and becomes negative for large Av (more negative than -1).

This seems nonsensical.

I believe the statements in the introduction and in the Derivation section should be that the Miller effect multiplies the capacitance by a factor of (1-Av), where Av is a negative number for the most frequently used amplifier configurations (i.e. common-emitter and common-source amplifiers), as a result of a 180-degree phase change between the input and output.

Note that if Av is negative, then (1-Av) results in a multiplication of the capacitance between the input and output.

Am I correct? Or do people think I'm the one who is confused? —The preceding unsigned comment was added by 129.82.228.111 (talk) 15:20, 12 April 2007 (UTC).

Are the signs correct?
In the derivation formulas there's some problem with signs, I think...I end up with (1+Av)..
 * Yes, there was a small mistake in the derivation. It should have been $$V_2 = A_V V_1$$ instead of $$V_2 = -A_V V_1$$. It should be ok now. Roger 15:37, 2 May 2007 (UTC)
 * Made some more changes, should hopefully be clearer now. Roger 16:16, 2 May 2007 (UTC)

Does negative capacitance make any sense? No really, this is about an inverting amplifier. Therefore $$V_o = - A_v V_i$$. Consequently it must be $$1 + A_v$$ everywhere. See also the referenced paper. --Mkretz (talk) 16:04, 26 January 2010 (UTC)


 * I've seen it as both $$1 - A_v$$ and $$1 + A_v$$ in the literature. I think $$1 - A_v$$ is more consistent and less confusing, since voltage gain is often negative (see the common emitter article, for example). Originally I had something like $$1 + |A_v|$$ to emphasize that the multiplication factor is usually greater than unity, but someone modified it.-Roger (talk) 19:46, 23 May 2011 (UTC)

It clearly makes no sense3 to assume -Av, I agree it's common, but it unnecessarily complicates the maths (+Av for -Av?!), and makes the derivation wrong. This only works while labelled as -Av, which in both places it is not, I've changed it to the correct value. The mistake people are making is that the original source says +Av, but that source has it's diagram indicating a gain of -Av. —Preceding unsigned comment added by 155.198.115.124 (talk) 08:26, 22 May 2011 (UTC)


 * I agree with Roger that $$1 - A_v$$ is the more universal expression covering both the inverting ($$-A_v$$) and noninverting amplifier ($$A_v$$) configurations. This form is suitable for the more general Miller theorem. As the Miller effect is a special case of Miller theorem, we can assume here only the inverting configuration: to denote the amplifier input with (-) and to use only $$1 + A_v$$ (i.e., to replace $$A_v$$ in $$1 - A_v$$ with $$-A_v$$:) Circuit dreamer (talk, contribs, email) 16:14, 24 May 2011 (UTC)


 * I also agree that it should be $$1 - A_v$$ . And if $$ A_v$$  should be positive then the input acts like a negative capacitor.  With a positive input capacitance, as you ramp the voltage in a positive direction, you source current into the input.  With a negative capacitance, as you ramp the voltage in a positive direction, you sink current from the input.Constant314 (talk) 20:11, 24 May 2011 (UTC)


 * Congratulations! You are ready to look at Miller theorem negative impedance applications, negative capacitor and INIC. Circuit dreamer (talk, contribs, email) 21:13, 24 May 2011 (UTC)

Translation into Chinese Wikipedia
The 19:30, 26 March 2008 Brews ohare version of this article is translated into Chinese Wikipedia.--Philopp (talk) 12:21, 25 May 2008 (UTC)

Article for Miller's Theorem
The introduction indicates that the Miller Effect is a special case of Miller's Theorem. If this is true, why does the link for Miller's Theorem redirect to this article? In other words, should a separate article exist to explain the general case of Miller's Theorem? —Preceding unsigned comment added by 128.187.0.164 (talk) 20:36, 4 September 2008 (UTC)


 * > "In other words, should a separate article exist to explain the general case of Miller's Theorem?"
 * Yes, it should :) Unfortunately no one has written one yet. If you are so inclined, then feel free to start one. I'm sure you'll get help once the initial article is created. -Roger (talk) 21:18, 4 September 2008 (UTC)

Figure 1
"Figure 2 shows an example of Figure 1 where the impedance coupling the input to the output is the coupling capacitor CC." There is no Figure 1. What might this sentence have meant? MrDemeanour (talk) 13:24, 27 April 2010 (UTC)
 * Looks like the figure was deleted at some point due to a copyright violation. I don't remember what it looked right, but hopefully someone will be able to recreate it. -Roger (talk) 21:31, 27 April 2010 (UTC)
 * Yes, it was deleted from Commons citing copyright violation. But this is a little baffling, it was moved to Commons from Wikipedia, and the Wikipedia history describes it as "Circuit for deriving the Miller effect. Made with Klunky," the uploader was one Roger Brent.  Roger, if this really is your self-created image I will undelete it.  Can you confirm?  Sp in ni  ng  Spark  20:20, 29 April 2010 (UTC)
 * Sorry I missed your reply. Indeed, I did create that image. Please restore it, thanks.-Roger (talk) 01:41, 11 May 2010 (UTC)
 * Done.  Sp in ni ng  Spark  19:37, 11 May 2010 (UTC)


 * Thanks! Do you know why they deleted my image, and how I can stop it from happening? -Roger (talk) 19:52, 11 May 2010 (UTC)

Op-amp Miller integrator (links)
http://www.google.bg/search?hl=en&q=miller+integrator+op+amp&aq=2&aqi=g4&aql=&oq=Miller+integrator&gs_rfai= http://www.electronics.dit.ie/staff/ypanarin/Lecture%20Notes/K235-1/5%20OpAmps%20Circuits.pdf (page 23) http://www.ee.lamar.edu/EELABS/ELEN3108/Lab10.pdf http://www.ece.utah.edu/~ece2210/Notes_OpAmp_F05.pdf Circuit dreamer (talk, contribs, email) 2:35 am, Today (UTC+3)

Op-Amp Integrator and HF transistor stages
I removed the link to op-amp integrators that was put here because it isn't relevant. The Miller effect, as it applies to junction capacitances in transistor stages, affects the HF roll-off of an amplifier. An op-amp integrator is a VLF (actually quasi-DC) circuit. There is very little in common between the two. Zen-in (talk) 01:36, 11 May 2010 (UTC)


 * Hey Zen-in. In a recent edit, you added the common collector as a way of buffering to reduce the Miller effect. That may be in some cases where the input impedance of the CC happens to be low, but in general (and ideally) it's high, so that wouldn't be completely accurate. The CB (and cascode) are the two best examples IMHO. -Roger (talk) 01:51, 11 May 2010 (UTC)


 * You are right about the input impedance of CC stages being high. It would be very difficult to design a CC stage with a low input impedance.  However it is the output of a CC buffer that is connected to a CE gain-producing stage.  The output impedance of a CC stage has a low impedance.  When that is shunted with COB of the CE stage, the time constant is much lower than if the CC buffer was not used.  A rough approximation of the HF roll-off of a transistor amplifier is calculated by taking the inverse sum of the HF time constants.  Since COB contributes the most to this, due to the Miller Effect, having a low source impedance makes a big difference.   A single CE stage might have a HF roll-off of 1-2 MHz, depending on the bias condition, gain, and FT of the transistor.  If a CC buffer is used in front, the roll-off will go up by a factor of 10 or more. Zen-in (talk) 03:02, 11 May 2010 (UTC)


 * Ah, you mean by lowering the impedance seen by $$C_M$$, rather than $$C_M$$ itself. In that case we should clarify the article to make a better distinction between the CB buffer and the CC buffer. -Roger (talk) 03:10, 11 May 2010 (UTC)


 * It may not be necessary. The Buffer amplifier page covers those details. You questioned my edits.  Does my answer above answer your question?  Zen-in (talk) 04:01, 11 May 2010 (UTC)


 * Well it confused me at first since I was thinking in terms of output buffers like the CB, so it's likely to confuse others as well. I'll work on fixing it sometime. -Roger (talk) 04:05, 11 May 2010 (UTC)


 * I see where the confusion comes from. I meant to say CC buffer in my edit comments instead of CE buffer. Zen-in (talk) 19:35, 11 May 2010 (UTC)

How to modify impedance
(enlarging and generalizing the Miller effect)

I have made major edit of the first part of the article with the purpose to reveal the essence of the Miller effect, to distinguish clearly the two basic configurations (inverting and non-inverting) implementing the Miller effect and to distinguish the two groups of applications (undesired and useful) illustrating them with popular examples.

The Miller's idea (modifying the current by adding a proportional voltage) is extremely simple, captivating and fascinating... and its implementation (connecting a varying voltage source in series to the impedance element) seems as a "clever trick", as an illusion... Imagine only how simple it is! For example, we have a resistor with resistance R but we need a bigger resistance; unfortunately, we have not such a resistor... What do we do then?

1. Subtracting Vout from Vz. (Vz is the voltage drop across the impedance Z and Vout is the additional voltage)

1.1. Increased impedance. As we are clever enough:), it flashes upon us to connect a proportional smaller voltage source contrary to the input source. The current decreases and we have the feeling that the resistance has increased! But this is an illusion since the actual resistance has remained unchanged; only the virtual resistor (the resistor + the opposing voltage source) behaves as a bigger resistance.

1.2. Infinite impedance. Now imagine we need an infinite resistance; so, we adjust the opposite voltage equal to the input one. The current stops flowing and we have the feeling that there is no resistor connected! This is the legendary bootstrapping idea; we have discussed it a week ago on op-amp page. All the op-amp inverting circuits with series negative feedback exhibit this property.

1.3. Negative impedance (INIC). Then, imagine we go too far in these funny experiments - we set the opposite voltage higher than the input one. What magic it is! The current reverses its direction; the resistor produces and pushes the current into the input source instead to consume and sink the current from the source. We have obtained a negative resistor with current inversion; we have converted the positive resistance R into negative -R!

2. Adding Vout to Vz.

2.1. Decreased impedance. Contrary, if we want to decrease the resistance, we connect a proportional smaller voltage source in the same direction to "help" the input source. Now, the current increases and we have the feeling that the resistance has decreased.

2.2. Zeroed impedance. Then, if we want to zero the resistance, we adjust the "helping" voltage equal to the voltage across the resistor. The current increases to its maximum (determined by the input voltage and the external element) and we have the feeling that there is a wire (instead the resistor) connected! All the op-amp inverting circuits with parallel negative feedback are based on this powerful idea.

2.3. Negative impedance (VNIC). Finally, imagine as above that we go too far and we adjust the "helping" voltage higher than the voltage drop across the resistor. Now, the resulting voltage changes its polarity (an external resistor has to be connected); the resistor produces and pushes a voltage into the circuit instead to consume a voltage drop. We have obtained another negative resistor but with voltage inversion; we have converted the positive resistance R into negative -R!

So, the Miller's idea gives us a powerful recipe for making various virtual elements: to modify artificially the impedance, just connect an additional proportional voltage source (the amp's output) in series to the initial element. Thus the combination of the initial actual element and the attached voltage source serves as a new virtual element (virtual element = actual element + proportional voltage source).

We can generalize the Miller's idea if we place all these six arrangements in the table below (the voltages are presented by their magnitudes):

BTW, the last arrangement - the negative impedance with voltage inversion, should not belong to Miller' effect. It was implemented later by combining a negative with positive feedback in the circuit of VNIC. For now, I have not added this case to the article. Please, discuss.

Circuit dreamer (talk, contribs, email) 08:37, 16 May 2010 (UTC)


 * Thank you for not adding that last arrangement. But IMHO everything else needed to go as well.  In your recent edits you talk about an infinite negative impedance.   How is that different from an open circuit?  Is Has this infinite negative impedance been observed in a lab and have any papers been written on the subject?   Zen-in (talk) 17:18, 16 May 2010 (UTC)


 * CF: I liked most of the reorganization you did in this edit, but some of the content changes are a bit too vague and probably fall under OR. I'm don't necessarily agree with Zen-in's reversion of everything, but I understand why he did it. Perhaps you should also try to make smaller edits so everyone can follow along one step at a time. -Roger (talk) 17:29, 16 May 2010 (UTC)


 * I would guess that it was the same reason I reverted it wholesale before it went to edit war, much too difficult to unpick the useful bits. But I second Roger's comment on the reorganisation.  Divisions for useful and unwanted applications adds something to the article.  If nothing else, it counters the misconception that the Miller effect is always unwanted.  Sp in ni  ng  Spark  17:45, 16 May 2010 (UTC)


 * Zen-in, as usual, you have not understood what is written... I have not talked about an "infinite negative impedance"; I have talked about a normal positive, increased positive, infinite positive (open circuit) and negative impedance with current inversion. These are the four typical circuit states when we increase the voltage of the opposing source: Vout = 0, 0 < Vout < Vz, Vout = Vz, Vout > Vz (see the table above). IMO, a bit earlier before Vout = Vz there is an "infinite positive impedance" and a bit later after Vout = Vz there is an "infinite negative impedance". BTW, have you understood what negative impedance is? If so, we may start rewriting negative resistance page...


 * The last arrangement is very interesting since it represents negative impedance converters with voltage inversion (VNIC); they are not considered in negative impedance converter. If you want to know how they operate, I could help you. Please, do not remove my edits; give a chance to other wikipedians to examine them. Thank you. Circuit dreamer (talk, contribs, email) 18:04, 16 May 2010 (UTC)


 * Actually no one except possibly yourself, understands what you have written. That defeats the purpose of an encyclopedia.  Under the heading Essence(?) " if the voltage is subtracted, an increased, infinite and negative impedance is obtained; if the voltage is added, the impedance is decreased up to zero. "  What is an increased infinite and negative impedance?  It doesn't help your case that everywhere you are equating circuit behavior to some flavor of negative resistance.  Granted, it spices up the article and maybe grabs the reader's attention.  But when the reader has to understand negative resistance first, it makes the article difficult to understand.  Zen-in (talk) 19:34, 16 May 2010 (UTC)


 * Agreed. Let's reorganize the page gradually and discuss. It seems Miller effect is a great phenomenon since so many circuits are based on it. Circuit dreamer (talk, contribs, email) 18:17, 16 May 2010 (UTC)


 * CF: please try to keep your edits citable. You have a unique approach to circuits that I'm not questioning, but it's hard for people unaccustomed to it to understand right away what you're explaining. That's one of the reasons I think it's best not to introduce a negative feedback perspective: if you don't yet know about NFB, then you can't gain anything from the article. -Roger (talk) 18:47, 16 May 2010 (UTC)

Commonly accepted meaning of Miller Effect
I'd comment that the article now seems to extrapolate beyond reason; from reading the article, it would appear that any negative-feedback arrangement can now be classified as the Miller effect! Do we have any sources that suggest the term "Miller effect" applies to anything other than the multiplication of the effective capacitance, when in an inverting-amplifier configuration? (For example, Googling for "Miller inductance" brings up nothing relevant.) If not, we should remove all mention of negative-impedance, etc.  Oli Filth(talk&#124;contribs) 16:51, 17 May 2010 (UTC)


 * I added another heading that includes Oli Filth's comments in the hope that the discussion will continue in this more constructive direction. The Miller Effect and Miller Capacitance mostly have to do with tube, FET, and BJT amplifiers.  A dominant pole, due to the multiplying effect of the gain on a Cgd or Cob and the source impedance, determines the HF roll-off.  This is what needs to be presented in the article.  Internal inductances are insignificant compared to these capacitances and don't need to be considered in depth.  Also I think the article needs to focus on transistor stages. The generalized amplifier case looks like it has been lifted from a textbook.  Zen-in (talk) 16:45, 19 May 2010 (UTC)


 * Well, I've already removed the weird stuff. You're right, we should probably mention that the Miller effect is most commonly encountered in transistors due to the large parasitic input-output capacitance.  However, any mention of dominant-pole compensation should probably leave out the details, and refer the user to the relevant article.  I'm also suggesting that we entirely ignore the Miller effect in the case of inductors and resistors because we'd need a source to state that the term is still relevant, and in any case it only serves to reduce R or L.  Oli Filth(talk&#124;contribs) 18:29, 19 May 2010 (UTC)


 * Oli Filth and Zen-in:
 * There are lots of sources that discuss the more generalized version of the Miller capacitance (i.e. the Miller Theorem), so we should definitely include a mention of it. I agree though, that we should focus on the capacitance version, since it's probably the most common; but it would be nice to include stuff on the general two-port Miller equivalence (Generalized Miller Theorem and Its Applications, Rathore, 1989), which includes equivalent impedance, resistance, etc. (thought I haven't come across an explicit mention of the term "Miller inductance"). I also agree that transistor/tube examples are probably the most common, but I see no need to limit the article solely to these devices.


 * Oh and I made the current diagram in the derivation section, and did some editing to that section, and I can assure you it wasn't (at least on my part) "lifted from a textbook" (there is a book called "Fundamentals of RF Circuit Design" by Everard that is quite similar, but I only recently became aware of it). -Roger (talk) 21:39, 19 May 2010 (UTC)


 * Curious; Everard was my tutor at uni!


 * Is the Miller effect a special case of the Miller theorem, or is the Miller theorem a generalisation of the Miller effect? So far as I understand, the Miller effect is the specific case in a -ve feedback amplifier, whereas the theorem relates to an arbitrary impedance between any two (not necessarily dependent) voltage points.  If we want to discuss the more general theorem in the article, may I suggest a move to Miller theorem?  Oli Filth(talk&#124;contribs) 22:11, 19 May 2010 (UTC)


 * Ha, quite a coincidence indeed!
 * Actually some authors seem to interchange "Miller effect" and "Miller theorem", but both seem to apply to the case of an impedance connected between the input and output terminals of an amplifier (or general network). More often than not, "Miller effect" seems to be assigned to the special capacitive case (which was the first studied by Miller). The generalized Miller theorem applies to any two two-port networks (in various series/parallel combinations).
 * I'm open to renaming/moving the article to be more general (I was actually thinking about proposing that). -Roger (talk) 00:18, 20 May 2010 (UTC)


 * This sounds like the way forward, but we should hash out here exactly what is covered by the general-purpose Miller theorem first. For example, this source agrees with you in that it's in the context of an amplifier (or more specifically, linearly dependent sources); however this source claims it's more general, i.e. any two voltage sources.  Oli Filth(talk&#124;contribs) 00:35, 20 May 2010 (UTC)


 * Good point. Miller's theorem can actually be applied to any impedance between two arbitrary voltage nodes, so even the capacitive case is more general than the current version of the article covers (the proof section also makes more assumptions than are necessary). I say we be as general as possible. -Roger (talk) 01:50, 20 May 2010 (UTC)

Is the Miller integrator based on the Miller effect?
Have you seen that the link to the most popular op-amp Miller integrator is removed with a comment "(rm unrelated reference)"?!? If so, why do you not restore the link? It turned out that there is no connection between the Miller integrator and the Miller effect?!?! Then let's invite some of our unprejudiced visitors to restore the link and to show that there is "some" connection between the two arrangements:
 * The Miller effect is observed in an inverting amplifier with a capacitor connected between the amp's output and input (as the article says)
 * The op-amp inverting integrator (frequently named Miller integrator) contains a capacitor connected between the op-amp's output and input.

Circuit dreamer (talk, contribs, email) 15:36, 20 May 2010 (UTC)

Is there any connection between the charge amplifier and the Miller effect?
Have you also seen that the link to charge amplifier is removed with a comment "(nothing in Charge amplifier mentions the Miller effect, nor vice versa)"? Let's look at the article to see what a charge amplifier (also referred to as a current integrator) is: "Charge amplifiers are usually constructed using op-amps with a feedback capacitor". That is, a charge amplifier is an op-amp with a capacitor connected between its output and input. But why? To understand why, we have to see the old revision that was removed as well...

I ask you again, "Will someone restore the link and show the connection between the charge amplifier (current integrator) and the Miller' arrangement to removers?" Circuit dreamer (talk, contribs, email) 16:18, 20 May 2010 (UTC)


 * I understand that. But there is currently nothing in either article which explicitly suggests that the other is relevant; any reader clicking on that "See also" link would have to work very hard to understand why they've been taken there.  That is why I removed the link.  Oli Filth(talk&#124;contribs) 17:50, 20 May 2010 (UTC)

Fig. 2 depicts a circuit with positive feedback.
Depending on Av of course, but for any Av > 1 the circuit is likely to be unstable. Constant314 (talk) 01:51, 15 June 2011 (UTC)

Impact on frequency response (errors)
--Circuit dreamer (talk, contribs, email) 13:51, 15 June 2011 (UTC)
 * The signs of the op-amp inputs in Fig. 2 are just wrong and do not correspond to the explanations below. They should be swapped as the figure represents an op-amp inverting integrator (not a circuit with positive feedback).
 * "The load is irrelevant to this discussion: it just provides a path for the current to leave the circuit" is wrong as well. The op-amp (not the load) is that "provides a path for the current". The current enters or exits the op-amp output, not the load.

Sign of Av
For readability the sign of Av should be made consistent throughout. Does anybody have an argument in favour of a particular sign, or shall I flip a coin? --catslash (talk) 20:18, 24 September 2012 (UTC)
 * I think it is easier to follow if Av is made a positive number rather than ask the reader to cope with double negatives in their head.  Spinning Spark  22:29, 24 September 2012 (UTC)

Done - for the Effects section, but the diagrams in the Impact on frequency response (previously called Common example) use Av for non-inverting amplifiers. --catslash (talk) 01:27, 25 September 2012 (UTC)
 * There is also the additional complication that the Miller capacitance should (but isn't) be shown as negative in the text since the circuit is essentially the same as the negative impedance converter. The diagrams can be changed, but I'm thinking an inverting amp example would be better since saying the gain is -Av with Av negative gets us back to the double negative issue.  Spinning  Spark  06:10, 25 September 2012 (UTC)


 * It has been several months and the pictures and text are still incompatible. I think most agree that it is the picture that should be changed.  I cannot fix the picture but I can replace it with my own picture.  The picture will not be an exact replacement.  In particular it will not have any equations as part of the picture.  That must be added in the text.  Also I have shown an explicit output resister for the amplifier that will need to be addressed in the text.  The reason for that is that most instances where the Miller effect is discussed involve active devices that do not have low output impedance and there is a Miller effect on the output impedance as well as the input impedance.  Finally, pictures 2 and 3 have been combined into a single picture with an A part and a B part.  I'll make the changes in two steps.  First I'll change the picture and then I'll change the text.  Here is the picture:


 * [[File:Miller Effect Illustration 1.png]]


 * I'll wait a day or so to hear objections and suggestions and would gladly agree for someone else to make the changes in the text. Constant314 (talk) 04:19, 27 March 2013 (UTC)


 * The only comment I have is that the symbols should match the text and follow normal mathematical conventions. In particular, the text has lower case variables for v. i etc.  Also, variables are conventionally italic (R, C etc) but their subscripts should be upright unless the subscript is itself a variable.  The text needs cleaning up for this last point as well as the diagram.  Spinning  Spark  13:15, 27 March 2013 (UTC)
 * I'll make those changes. Regarding variables and constants, I 've always regarded the voltages and currents as variables and the impedances as constants.Constant314 (talk) 15:31, 27 March 2013 (UTC)


 * I lied, one other thing, you have some spurious blue inside the capacitor symbols and also on the line going from the amp + terminal.  Spinning Spark  13:17, 27 March 2013 (UTC)
 * You have a good eye to spot the blue on the line to the amplifier input. That was definitely unintended.  I've always liked to put a little color between the capacitor plates but I'll make it white if you object.Constant314 (talk) 15:31, 27 March 2013 (UTC)
 * I'm fine with the colour on the capacitors if you want it like that. They must be audio polyester dialectric rather than RF air gaps.  Spinning  Spark  16:25, 27 March 2013 (UTC)
 * I have made the changes you suggested. I'm not entirely happy with the font which is Times New Roman.  By the way, do you have a link that descibes the "normal mathmatical conventions"?Constant314 (talk) 21:50, 27 March 2013 (UTC)
 * See MOS:MATH.  Spinning Spark  22:25, 27 March 2013 (UTC)
 * I looked in four or five electronics books and what I found was that lower case italic is used for v and i when they are funtions of time, but upper case is used for phasors. Some authors use italic and at least one uses bold non-italic.  The text in the related section seems to be using the variables as phasors, so, do you still want lower case letters?Constant314 (talk) 04:28, 28 March 2013 (UTC)
 * You are absolutely right about the case, that is indeed the normal convention. The article expressions should be changed, expressions involving $$j \omega v$$ are definitely wrong.  One can't have a time varying quantity multiplied bt $$j \omega$$, it isn't physical.  Sorry, I had not looked too closely at what the expressions in the article were saying, just saw that they were lower case.  Upright (and frequently upright bold) is often used for vectors, matrices, tensors, sets etc.  Phasors are none of these, mathematically they are ordinary (complex) variables and thus should be upper case italic.  Most good textbooks follow this convention, certainly all my undergraduate books do.  There is an ISO standard on this subject if you're interested.  Spinning  Spark  07:41, 28 March 2013 (UTC)
 * The entire section is about frequency response. I think I will go with phasors through out.  That means the schematic goes to upper case, italic, not bold letters for V and I.  Do you concur?Constant314 (talk) 20:58, 28 March 2013 (UTC)
 * Go for it. Spinning Spark  00:47, 29 March 2013 (UTC)
 * It's done. In the end I went more minimal change.Constant314 (talk) 00:03, 31 March 2013 (UTC)

Massively confused article
There are so many things wrong with the article I would not take on the corrections myself. The errors come from a general lack of understanding of the three domains: time; frequency; and energy resulting in a mishmash of bandwidth (frequency domain) and slew rate (time domain) effects. As example, a "Miller capacitor" added to a typical current input voltage output transconductance single transistor stage has no effect on the bandwidth of the circuit. The capacitor does have substantial effect on slew rate which is a time domain effect and not even related to the frequency domain other than as a slew rate limit. The very clear lack of comprehension of these three domains is where most go very wrong and this article is no exception. In the end, this comment will be ignored or deleted as the domain concepts are almost completely beyond the capacity of the vast majority of persons that would be involved in such design or development activities and writing of such an article. Many will consider this writer a heretic and view negatively this correct view. See Richard C. Heyser, Hilbert, Poppe, and Rene Thom for more correct information. It would be very nice if someone had the ambition and real knowledge to fix this important article.71.158.227.108 (talk) 03:39, 27 September 2012 (UTC)
 * As someone who does understand the difference between the time and frequency domains (and even how to transform between them), I would say that it would be massively more helpful if you concentrated on specific examples of where the article could be improved rather than insulting previous authors who you really have no idea who they are or what they are capable of. It also helps to provide links when you cite sources - or at least give the full citation (journal, date etc) so we can actually find it.   Spinning  Spark  10:01, 27 September 2012 (UTC)
 * So you can transform between time domain and frequency domain? Is that point by point?  If so you are also confused.  Only statistical mapping can be done between domains.  Please read Richard Heyser, http://www.amazon.com/Richard-C.-Heyser/e/B001KCEXK0 70.252.138.199 (talk) 17:08, 22 March 2013 (UTC)

it seems the last equation lost a - sign.
it seems the last equation should be:
 * $$ V _o =- A_v V _i =- A_v \frac { V _A} {1+j \omega C_M R_A}, $$ — Preceding unsigned comment added by Fkhp101 (talk • contribs) 05:56, 11 February 2014 (UTC)


 * Fixed  Spinning Spark  14:08, 13 February 2014 (UTC)