Talk:Negative-feedback amplifier

Patent mentioned
Can someone confirm that the patent mentioned (2,102,671) is a US patent, that it really is by Black, and from which year it is.

From one reference list the patent number is 2,102,761, and is from 1937..

Related to feedback amplifiers is the asymptotic gain model.

The formula pertains to a difference input, but the figure uses a summer. —Preceding unsigned comment added by 85.166.73.253 (talk) 12:43, 19 January 2008 (UTC)
 * Changed figure - thanks Brews ohare (talk) 06:10, 24 January 2008 (UTC)

The patent number (2,102,671) is correct, and it was issued on December 21, 1937. This was more than 9 years after the original invention was submitted on August 8, 1928. Harold Black states that, "One reason for the delay was that the concept was so contrary to established beliefs that the Patent Office initially did not believe it would work." Black recounts this, and other interesting facts, in an article he wrote for the IEEE Spectrum in Dec. 1977 entitled, "Inventing the negative feedback amplifier." I have a pdf of this article and would be happy to upload it as soon as I figure out how. I'm new to Wikipedia.Rtborn (talk) 20:27, 29 October 2008 (UTC)

Op Amp Applications Handbook, edited by Walt Jung (Newnes, 2006) page H3 of Op Amp History (this section was written by Walt Jung), says that Black was working for Western Electric Company when he came up with the idea of negative feedback (not Bell Labs as stated in the article).194.75.159.78 (talk) 10:54, 10 February 2010 (UTC)

Clarification
I'm not sure what the note "A subtle point is that the main amplifier may not be a two port" means. Clarification please? -Roger (talk) 00:11, 24 January 2008 (UTC)
 * I tried a clarification. See how it sits. Brews ohare (talk) 01:56, 24 January 2008 (UTC)
 * I have removed the obscurity by referring the reader to Jaeger.

Brews ohare (talk) 15:06, 24 January 2008 (UTC)
 * I've also added a final section that explains the importance of the port condition.

Brews ohare (talk) 02:00, 26 January 2008 (UTC)

Cons: The gain of the amplifier is decreased
I hardly think this is a con; not everybody wants an amplification of 10^6 from their op-amps! —Preceding unsigned comment added by 195.137.110.134 (talk) 19:10, 1 April 2010 (UTC)

About the removed links on 00:08, September 21, 2010
Zen-in, should I explain to you that the common-collector amplifying stage is the most typical transistor negative feedback amplifier? So, it deserves at least a humble link. Then, should I educate you about the most elementary op-amp negative feedback amplifier (buffer amplifier, op-amp voltage follower)? And finally, should I tell to you that 14 of all the 18 op-amp applications are negative feedback circuits? Please, restore the links. Circuit dreamer (talk, contribs, email) 20:38, 23 September 2010 (UTC)


 * There are many thousands of electronic circuits that use negative feedback. Should each one be listed here?  This article is a very concise treatment of generalized feedback amplifiers.   The Op-Amp circuits are more specific cases.  Too much unnecessary detail makes an article unreadable.  You would be serving Wikipedia better by trying to clean up some of the articles you have written instead of trying to re-write what is already a very well written article.Zen-in (talk) 17:14, 24 September 2010 (UTC)


 * Your assertions are absurd and nonsensical as all your existence in Wikipedia... Can you distinguish between "many thousands of electronic circuits that use negative feedback" and the two main, basic, fundamental negative feedback circuits (transistor and op-amp voltage follower)? Can you distinguish between "any" and "the most important" negative feedback applications? These humble circuits are the most elementary but fundamental implementations of the generalized negative feedback amplifier. They are presented in every electronics book and resource considering the topic; they are legend. Circuit dreamer (talk, contribs, email) 06:05, 25 September 2010 (UTC)

About the restoration of the previous edit
I have restored my last edit (05:18, September 24, 2010). Actually, the negative feedback analysis is the same but more consistent and concise (5 instead 8 expressions). I have removed some redundant expressions as:

Vout = AOL V''in,  $$A_\mathrm{OL} = \frac{V_\mathrm{out}}{V_\mathrm{in}} \ ,$$,   $$A_\mathrm{fb} = \frac{V_\mathrm{out}}{V_\mathrm{in}}$$,   $$A_\mathrm{OL} = \frac{V_\mathrm{out}}{V'_\mathrm{in}}$$.

I have renamed the title of the section with more meaningfull. I have also described more precisely the negative feedback arangement introducing a summer (subtractor) component in the block diagram and linking the text to this arrangement. Circuit dreamer (talk, contribs, email) 20:25, 3 October 2010 (UTC)

Is the main amplifier block a two port.
The discussion of Fig. 7 doesn't seem to match the actual figure. — Preceding unsigned comment added by 122.110.119.35 (talk) 02:18, 22 June 2012 (UTC)


 * The top half of the diagram is missing labels for components and currents. ~Kvng (talk) 21:09, 28 August 2015 (UTC)

Tweaked intro
I've just removed a few puzzling claims in the introduction, namely that an emitter follower and an op-amp follower are examples negative-feedback devices in which the feedback network is absent. In the case of the emitter follower, it's true that there's no feedback network, but this means it's not an example of negative feedback. In the case of the op-amp follower, the claim that there's no feedback network is just plain wrong. Zueignung (talk) 05:40, 22 December 2012 (UTC)

External links modified (February 2018)
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One over beta
What is this called? Not quite noise gain.

"the noise gain and the 1/β curve are the same—until they intercept with the gain-magnitude curve. After that, the noise gain rolls off with the amplifier open-loop response but the 1/β curve continues on its path." - Jerald Graeme

— Omegatron (talk) 15:38, 12 March 2019 (UTC)

Negative-feedback isolation amplifier
Is that possible for a negative feedback amplifier to be floating-common and have tolerance to common-mode voltages? Could it also have channel-to-channel as well as input-to-output isolation? - WorldQuestioneer (talk) 23:04, 20 January 2020 (UTC)