Talk:Negative feedback/Archive 4

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Dicklyon's further reversions

clear consensus against Brews ohare's changes and otherwise this is going nowhere
The following discussion has been closed. Please do not modify it.
In this massive revert Dicklyon removed many different topics raised in the section Negative feedback amplifier with no Talk page discussion but only the erroneous one-line Edit Summary: Tangential bloat, not supported by the cited sources. Before these reverts the original subsection contained the observation: The difference signal I–βO that is applied to the open-loop amplifier is sometimes called the "error signal". The output is the open-loop gain times this error signal, added to any disturbance D that may be present. In the absence of a disturbance D, this signal is given by:1 $I-\beta O=I\left(1-\beta {\frac {O}{I}}\right)={\frac {I}{1+\beta A}}\ ,$ which is determined by the independent parameters I (set by the signal source), A (set by the open-loop gain) and β (set by the feedback network), and therefore is set by these external variables, unlike more sophisticated feedback control of errors using internal state variables of the controlled system.2,3,4 This error signal tends to be small if the open-loop gain A is large. Notes 1Muhammad Rashid (2010). "§10.3.1 Closed-loop gain – Equation 10.7". Microelectronic Circuits: Analysis and design (2nd ed.). Cengage Learning. pp. 644–645. ISBN 9781133007487. 2Boris Lurie, Paul Enright (2000). Classical feedback control with MATLAB. CRC Press. p. xiii. ISBN 9780824703707. 3Shimon Y. Nof (2009). "§4.7: The emergence of modern control theory". Springer handbook of automation. Springer Science & Business Media. pp. 63 ff. ISBN 9783540788317. 4D Roy Choudhury (2005). "Chapter 11: State-variable formulation". Modern control engineering. PHI Learning Pvt. Ltd. pp. 522 ff. ISBN 9788120321960. Comments Dicklyon claims that this material is not supported by the cited sources. I find that claim invalid. Dicklyon also claims this material is "tangential bloat", again an unsupportable contention. Brews ohare (talk) 18:30, 30 November 2014 (UTC) I thought it was tangential and unnecessary, more appropriate in a sub-article. I agree with the removal of this material from this summary article. Binksternet (talk) 19:29, 30 November 2014 (UTC) Also concur. Since both sections have links to dedicated pages, the extra detail here serves no purpose. Trevithj (talk) 20:47, 30 November 2014 (UTC) Binksternet, of course. saying you thought it tangential is your view, and without any argument to support it, it becomes just a 'me too' alongside Dick's view, also unsupported. Of course, it is always gratifying to have 'me too' support, but WP is not based upon a 'me too' count, but is a presentation of sourced opinion, with topics chosen according to sources. The reasoning as to why this is relevant, beyond the fact that published authors think it worth including in their treatments, is that the use of the feedback amplifier involves an 'error signal' that is not determined in the same way as the 'error' in controllers that determine the system errors using internal state variables of the controlled system. This difference underlies the reason why the feedback amplifier can be used as a controller only for systems with simple input/output characterization. The sources cited elaborate upon thsese points. Brews ohare (talk) 20:55, 30 November 2014 (UTC) Trevithj: You suggest that links to dedicated pages obviates any need to point out the relevance of these topics, or to source them. And with the reversions of Dicklyon, there are in fact no links left to the respective pages on full state feedback and state-space feedback. As a general rule, the existence of more extensive articles is not a reason to avoid pointing out the relevance of a topic. Brews ohare (talk) 20:55, 30 November 2014 (UTC) In these edits that I reverted, Brews has introduced the state-space approach, apparently because he thinks it supports his thesis that amplifiers are somehow fundamentally different in concept from control uses of negative feedback. The logic of twisted interferences from sources is so bizarre and flawed that I can't begin to point out its errors. Reverting was the only easy way to contineu to protect the article from the abuse it gets from Brews when I go away for a while. Dicklyon (talk) 03:58, 1 December 2014 (UTC) Brews ohare, if you are trying to tell the reader that the negative feedback amplifier uses a control mechanism more suitable to relatively simple I/O than other methods of feedback, why don't you say it in so many words, without resorting to a proof of the concept? However, I don't see the literature supporting this view, that it is such a different beast. Binksternet (talk) 05:26, 1 December 2014 (UTC) Dicklyon: The process by which I arrived at the sources provided was explained to you at length on your talk page, which you seem to have failed to read. The basic issue you raised yourself was that the negative feedback amplifier was a form of controller. You dug up the Lurie & Enright source that refer to this as "classical control" and say "Classical design does not utilize the plant's internal variables and/or their estimates for compensation, unlike the full-state approach."1 They point out further that in classical control "the object of control (plant) is characterized either by its measured frequency response over the range of effective feedback or by a rather simple input/output mathematical model".2 It appears from their examples where a negative feedback amplifier acts as a controller, it controls one of these "plants" with a "simple input/output mathematical model", an example being a simple resistor. I fail to see anything hard to follow here, and am inclined to think you have not looked at the linked sources. Brews ohare (talk) 06:32, 1 December 2014 (UTC) Binksternet: You comment: " if you are trying to tell the reader that the negative feedback amplifier uses a control mechanism more suitable to relatively simple I/O than other methods of feedback, why don't you say it in so many words, without resorting to a proof of the concept?" I did not aim at a "proof" of anything. My object was to direct the reader to sources where the differences were noted. For example, here you will find the comment: "The transfer function approach confines to input-output behavior of linear systems only. On the contrary the state-space representation gives information about the internal behaviour of the system as well as information about its input-output behaviour...Hence, through the state-variable approach, perfect control of the system is possible" Here you will find: "Classical design does not utilize the plant's internal variables and/or their estimates for compensation, unlike the full-state feedback approach. ...These are the reasons this book [does not begin] with extensive plant modeling." Here you will read: "The state variables allowed for a more sophisticated representation of dynamic behaviour than the classical single-input single-output system modelled by a differential equation..." and later "Digital adaptive control, however, offers much greater possibilities for (1) Identification of relevant system parameters (2) Making decisions about the required modifications... (3) Implementing the changes." Binksternet, as presented in this thread, I attempted to summarize the discussion of these sources and lead the reader to them. I do not think pointing out the extreme limitations of the negative feedback amplifier as a controller and leading the reader to a broader understanding is out of place here, nor is it an expression of my ideas, but rather that of numerous sources, only three of which are noted here. So, what I am trying to say in broad terms is: "the negative feedback amplifier as a controller is suitable only for control of relatively simple single-input single-output systems, and much more limited in its use of feedback than other feedback approaches in common use that use internal variables and complex modeling of the controlled system and the response to its variations." If the presentation is unclear, perhaps you could assist in improving it? Brews ohare (talk) 16:17, 1 December 2014 (UTC) Binksternet, perhaps your reference to a proof is to the thread immediately above? That thread describes the "error signal" for the feedback amplifier and identifies its reliance upon external variables A, β, and I, as a contrast to the use of internal variables referred to by the sources just mentioned. You may regard this discussion as overkill, but the other editors on this page are very anxious that it not be presented because they do not admit there is any fundamental difference between controllers using negative feedback. Brews ohare (talk) 17:30, 1 December 2014 (UTC) Conclusion There being no attempt here to support the idea that placing the negative feedback amplifier in the context of modern control theory is "tangential bloat", and it being perfectly obvious that all statements in the material reverted by Dicklyon are supported by reputable sources, I propose to revert Dicklyon's action. Any objections, or perhaps, suggested reformulations? Brews ohare (talk) 13:53, 3 December 2014 (UTC) It seems like an elaborate setup for an odd point of view; for example, your conclusion "therefore is set by these external variables, unlike more sophisticated feedback control of errors using internal state variables of the controlled system". Is there a source that draws such a conclusion? How is the simpler case unlike the more complex case, other than having a 1D state variable? Dicklyon (talk) 15:33, 3 December 2014 (UTC) Dick, I don't know how you can miss what has been said and sourced over and over. The error signal employed by the negative feedback amplifier as derived by Rashid shows it to depend upon A, β , and the input signal I, all of which are external variables completely unrelated to the state of the controlled object or "plant". The three quotes above from three separate sources all show that, in contrast, the full-state or state-space controllers all make use of internal variables identifying the state of the controlled object. Do you get this? Brews ohare (talk) 15:43, 3 December 2014 (UTC) In addition, the sources all make a distinction between "classical" control, in which they include control using the negative feedback amplifier, and "modern" control (post 1956 according to Choudhury) based upon the development of systems that incorporate internal variables of the controlled object, also known as essential variables. Brews ohare (talk) 15:57, 3 December 2014 (UTC) There is no difficulty in treating the negative feedback amplifier as a control system using either classical or modern methods; I don't see you producing a source that suggests there would be. It is just a simple case, for which the modern methods offer no particular advantage. There is no source that suggests that the error signal does not depend explicitly on the output. The algebra is just for computing a gain under the model that the output is purely an open-loop gain times the input; that's a model, not a suggestion of how it works. Dicklyon (talk) 16:20, 3 December 2014 (UTC) Your concept "the negative feedback amplifier as a controller" is also very odd. We can describe the negative feedback amplifier as an example of a feedback control system, but "as a controller" is a weird twist, the motivation for which escapes me. Are there sources that do this? Your claim that the error signal is "completely unrelated to the state of the controlled object or 'plant'" remains bizarre, and contradicted by sources that I pointed out in which the 'plant' is identified with the amplifier output stage and/or load; it's feedback from this plant that makes the error signal. And I don't have time to waste on continuing this silly circus of yours. Just give it up. Dicklyon (talk) 16:05, 3 December 2014 (UTC) Dick, you have this all wrong, and simply refuse to understand the sources. If you want to come to grips here, try addressing the quotations from sources above. If you can construe them differently, do so. Otherwise your remarks are just bluster and avoidance. Brews ohare (talk) 16:13, 3 December 2014 (UTC) I have no quarrel with any of the quotations from sources. I have quoted a few parts of your text that don't follow from them. Enough. Dicklyon (talk) 16:22, 3 December 2014 (UTC) No , Dick. It is not enough. You have not quoted parts of my text that do not follow from the sources, and for a simple reason - there aren't any. Looking at the text here and the text here you have not identified anything that is contrary to sources. You have identified your own confusion about what the sources say, which you could clear up by comparing your remarks with these sources. For example, you say "Your concept [of] 'the negative feedback amplifier as a controller' is also very odd." And yet that is exactly what is done by Lurie and Enright who illustrate a voltage regulator in which they say "the plant is the load resistor RL", and the voltage across it is controlled by a negative feedback amplifier (in the form of an op amp), regulating the output voltage. "The command is the 5V input voltage (when the command is constant, as in this case, it is commonly called a reference, and the control system is called a regulator)." Brews ohare (talk) 18:50, 3 December 2014 (UTC) To continue, Dick, you say "Your claim that the error signal is "completely unrelated to the state of the controlled object or 'plant'" remains bizarre, and contradicted by sources that I pointed out in which the 'plant' is identified with the amplifier output stage and/or load". Now, the two parts of this sentence contradict each other. There is no doubt that it may be that the "load" is a simple resistor, as in the example above from Lurie and Enright. A resistor exhibits the properties of a single-input single-output system as described by these authors (what they refer to as a plant having a "simple input/output mathematical model" 1), and identified with these words in the reverted text. So there is nothing contradictory found here. However, the first part of your sentence, "Your claim that the error signal is 'completely unrelated to the state of the controlled object or ‘plant’' remains bizarre" is simply out to lunch. The error signal in the negative feedback amplifier, as defined by Rashid's Eq. 10.7, is determined by the externally determined variables A, β, and I, none of which have any connection with the load resistor at all. For example, the load resistor can fluctuate in resistance, and the 'error signal' I/(1+βA) doesn't change. Dick, please put aside your overwhelming desire to squelch all mention of differences between feedback controllers and look at the sources. Brews ohare (talk) 19:12, 3 December 2014 (UTC) Brews, you better find someone who supports your analysis to explain it better, as I'm still not getting it. Everything you say seems wrong to me. I have no desire to "squelch all mention of differences between feedback controllers", though it's not clear to me what kind of differences might be relevant to this article. Maybe someone else can point out differences that you're finding that would be relevant to the article on negative feedback. Dicklyon (talk) 19:29, 3 December 2014 (UTC) To me it looks like Brews ohare is trying to use Wikipedia to prove a point which is either not important or not at all supported. In the first case the matter is not widely discussed in the literature, so it doesn't seem like Wikipedia should pay disproportionate attention to it. In the second case I would recommend publishing a treatise elsewhere. Binksternet (talk) 20:07, 3 December 2014 (UTC) If Brews Ohare was an acknowledged expert on this stuff, but in fact not so long ago he didn't even know what an opamp was, and he is taking positions that literally nobody else agrees with. There is zero chance that others will agree, and this talk page consists entirely of Brews Ohare arguing, entirely unpersuasively, with everyone else. Given that, it's not profitable for it to continue. I propose to collapse this thread.GliderMaven (talk) 20:33, 3 December 2014 (UTC) Yes collapse this and the one above. I have stayed out of the content dispute as I do not have the time for it but ignoring me there are four editors rejecting Brews ohare's changes with good reason and so a clear consensus against them. This is about changes to the article, his changes have been rejected. That's not going to change and this should end.--JohnBlackburnewordsdeeds 23:12, 3 December 2014 (UTC) The point here is not who is an expert here, but what the sources say. I am the only one here using sources. Some of you want to say the quotes I have used to express the content of these sources are defective, but none of you has provided a source-based alternative. All you have is some fuzzy conceptions of your own, that you are unwilling to support with links to sourced text. Maybe you all have persuaded yourselves that something is amiss here, but it appears to be a case of groupthink, detached from published material. Brews ohare (talk) 22:30, 3 December 2014 (UTC) It seems to me that if you read this reverted text and the notes accompanying it you will find it is a nearly verbatim version of what these sources say. Assuming that is the case, the only question is whether it is pertinent. I'd say setting the negative feedback amplifier in its use as a controller in the context of full-state and state-variable control is entirely pertinent and that is all that is done here. So far no-one has addressed this matter directly. Brews ohare (talk) 22:57, 3 December 2014 (UTC) If you read this second block of reverted text it consists of Rashid's formula for the error signal he defines for the negative feedback amplifier, and the observation that A, β and the external signal I are external variables (which no-one can dispute) while the full-state and state-variable approach involves internal variables, as stated explicitly by the three cited sources. There is no dispute about these matters, and they separate the negative feedback amplifier from the so-called "modern" state-space approach. Dicklyon has raised questions about the limitations of Rashid's analysis when fluctuations are present, and these are dealt with by the introduction of the disturbance D in the Negative feedback amplifier section. They do not impact Rashid's formulation in the present context of separating "classical" from "modern" feedback control. This entire brouhaha is due to failure to concentrate upon what is being said and failure to directly address what the sources have to say. That problem would be avoided if critics would stick to sources, not using proxy summaries about personal concepts of what the sources say, but actually using the explicit text from sources to support their assertions. If this were done, it would soon evolve that any issues here are actually over other matters not raised in these two reverted contributions. Brews ohare (talk) 23:30, 3 December 2014 (UTC) There is so much to disagree with here that one can't even start. If you'd like to propose some points in smaller increments, we can discuss. For example, we've been all around on the use of Rashid's formula and the weird unsourced conclusions that you draw from it (like where you say "There is no dispute about these matters" followed by another bit of unsupported synthesis that "they separate the negative feedback amplifier from the so-called 'modern' state-space approach"). How do you separate an application of negative feedback from an approach that could be applied to it? The meaning and logic there escape me; no source supports these conclusions. Dicklyon (talk) 02:12, 4 December 2014 (UTC) Brews ohare, you are exhausting the community's patience and wasting everybody's time. Please stand down on your own terms or I will initiate a topic ban discussion. Binksternet (talk) 02:53, 4 December 2014 (UTC) I do not understand this hostility. It would seem that you all think you have explained yourselves blue in the face, yet not one of you has addressed the three sources cited in the reverted material. And no-one but Dick has addressed Rashid's standard formula for the error signal, which he agrees with under Rashid's assumptions, as well he might as his is the standard treatment in every textbook for the last 60 years. I am left thinking that none of you knows how to address the points raised, and certainly not by reference to sources. So be it, I guess. Brews ohare (talk) 03:27, 4 December 2014 (UTC) I'd like to point out that there is next to no connection between the collapsed discussions on this talk page that concern how the negative feedback amplifier itself operates, and in particular, the adequacy of Rashid's formulation for the ideal amplifer when faced with reality, and the present discussion that concerns the use of the ideal amplifier as a controller, a point I am confident that none of the critics here have grasped. Brews ohare (talk) 13:34, 4 December 2014 (UTC) The hostility could have something do with 6 years of stupid arguments, in which you have been banned for a year more than once for disruptive non-cooperative editing style. It's no surprise that you don't understand this. Dicklyon (talk) 02:15, 5 December 2014 (UTC) Dick, your referring to "years of stupid arguments" seems to suggest their stupidity originates with myself. However, the true origin, as demonstrated by this instance as one example, is a refusal by yourself and others to address the goal of WP to present sourced material, and the refusal to use Talk pages to discuss what sources say, rather than to pontificate over self-congratulatory imagined personal expertise. Your approach to the negative feedback amplifier doesn't address sourced topics, revealed by a simple mouse click on provided Google book links and supported by verbatim quotes, but relies upon your own (unsourced, and often off-topic) opinions and prejudices. Brews ohare (talk) 15:50, 5 December 2014 (UTC) For example, if this material were addressed directly by considering the references cited rather than a one-line cryptic edit summary Tangential bloat, not supported by the cited sources it would assist me to understand what you are talking about. When taken to the Talk page you say Brews has introduced the state-space approach, apparently because he thinks it supports his thesis that amplifiers are somehow fundamentally different in concept from control uses of negative feedback. This comment seems to say the state-space approach is my idea, when the cited sources bring it up. It also suggests that I am "supporting his [my personal] thesis", which again suggests this is my idea, and then completely misconstrues the point as (in your words) amplifiers are somehow fundamentally different in concept from control uses of negative feedback. This is not what the cited sources say, and not my representation of what these sources say. The "thesis" presented by these sources is that the use of negative feedback amplifiers (as controllers) is restricted to control of simple input/output objects, while more general state-space controllers use internal variables as well to achieve control over more sophisticated objects. If you directed your comments to the sources instead of searching for some pretext to throw brickbats at me, this matter could be engaged much less heatedly and to better end. Brews ohare (talk) 17:32, 5 December 2014 (UTC) The simple guideline is that discussion of what sources say is liable to be less controversial, less ego-engaging, and less subject to idées fixe than discussion of projected or even accurate perceptions of what WP editors happen to think. It also is what is germane to the WP project. Brews ohare (talk) 17:45, 5 December 2014 (UTC) This discussion is all about what sources say, which none of us disagree with, and your synthesis, interpretations, and conclusion from them, which we all disagree with. It's the same long-standing pattern that has made working with you impossible on so many other articles. Nothing new here. Dicklyon (talk) 20:30, 5 December 2014 (UTC)

Dicklyon's comment

Unproductive discussion collapsed
The following discussion has been closed. Please do not modify it.
Dicklyon says above: This discussion is all about what sources say, which none of us disagree with, and your synthesis, interpretations, and conclusion from them, which we all disagree with. It's the same long-standing pattern that has made working with you impossible on so many other articles. Nothing new here. Dicklyon (talk) 20:30, 5 December 2014 (UTC) This remark is confusing. It claims synthesis, interpretation and conclusions using absolutely no supporting diffs or comparisons with sources. So it is difficult to know what exactly is being labeled as unsourced synthesis, unsourced interpretation, and unsourced conclusion. What adds to the confusion is that it says while everybody disagrees with this unspecified material, "this discussion is all about what sources say, which none of us disagree with". And yet in reverting this material and this material the only sources discussed are those cited in the reverted material, and the only editor discussing these sources is myself. No editor on this page has presented anything from these or other sources to support Dicklyon's claims either that all assembled agree with these sources, or that I have misconstrued them in some unfathomable manner. This remark by Dicklyon is just one more example of venting, and has no relation to understanding the sources or presenting them properly. I recommend that in place of such attacks, the sources be addressed. For example, here you will find the comment: "The transfer function approach confines to input-output behavior of linear systems only. On the contrary the state-space representation gives information about the internal behaviour of the system as well as information about its input-output behaviour...Hence, through the state-variable approach, perfect control of the system is possible" Here you will find: "Classical design does not utilize the plant's internal variables and/or their estimates for compensation, unlike the full-state feedback approach. ...These are the reasons this book [does not begin] with extensive plant modeling." Here you will read: "The state variables allowed for a more sophisticated representation of dynamic behaviour than the classical single-input single-output system modelled by a differential equation..." and later "Digital adaptive control, however, offers much greater possibilities for (1) Identification of relevant system parameters (2) Making decisions about the required modifications... (3) Implementing the changes." Perhaps Dicklyon can express whether he agrees with these sources, and can express what should be changed in this or this reverted presentation that would reflect these sources more accurately? I suspect that the only objection that can be rasied is that the negative feedback amplifier is not mentioned explicitly in these quotes. If there is any real doubt that the negative feedback amplifier is included in what is referred to as "classical" control systems or the "transfer function approach" or that it is limited to control of simple input/output objects, that objection can be rapidly dispelled by further quotes from these sources, which apparently Dicklyon has yet to comprehend. In fact, this objection has been met in exactly this manner already in this thread. Brews ohare (talk) 21:11, 5 December 2014 (UTC) The only thing I'd quibble with in those quotes is where he says "Hence, through the state-variable approach, perfect control of the system is possible." But the remark is tempered on made more sensible in the gray box on the same page, so no problem there. As for your conclusion that the negative feedback amplifier is "is limited to control of simple input/output objects", I don't even know what that means. The negative-feedback amplifier is an example of a control system, which can be analysed by either classical or modern state-space approaches. Did you have a source saying that it cannot be handled by state-space approaches? Dicklyon (talk) 21:22, 5 December 2014 (UTC) Again Dick, what is said is that the negative feedback amplifier is limited in what objects it can control, and the general state-variable controller has wider applicability. This point is made emphatically in the above verbatim quotes already supplied for all three sources that refer to state-variable or full-state feedback controllers. Brews ohare (talk) 21:54, 5 December 2014 (UTC) You have to accept, of course, that for the first quote, the negative feedback amplifier is subsumed under "the transfer function approach". For the second quote, under "classical design". And for the third quote, under "classical SISO". You may be unwilling to do that, although the thread immediately above tries to address this point. Brews ohare (talk) 22:58, 5 December 2014 (UTC) The subject is not whether the general analysis of state-feedback controllers can handle the simple case of the negative feedback amplifier. The point is that the negative feedback amplifier does not involve full-state feedback of internal variables of the controlled object, and doesn't require this aspect of the state-space approach, while "modern" controllers do. Brews ohare (talk) 23:15, 5 December 2014 (UTC)

Failure on all sides

Binksternet has now filed an edit war protest asking for Adminstrator blockage of further discussion here by Brews ohare. My removal of annoying hatting to conceal my arguments on the Talk page is not, of course, about actual content, but about editors' aggressive activities to suppress even the discussion of content. I had hoped that direct discussion of sources and verbatim quotes from them might occur, but that has not happened despite Google book links directly to these quotes and my request for input upon their presentation and context. Although WP is supposed to present what sources say, and Talk pages are supposed to discuss sources and their presentation directly, the editors here have avoided this activity in favor of others. An unfortunate choice, and it leaves me disappointed, not so much for this topic, but for the depressing lack of interest in collaboration.

It seems I have not succeeded in raising any curiosity among the editors here, or any enthusiasm for writing a better article. In the face of the idées fixe assembled here, I can't do more to generate interest in a fuller presentation of this topic and the vast literature surrounding it, so I'll leave things as they are. Brews ohare (talk) 16:09, 6 December 2014 (UTC)

If you'll stay out of the way, interest in working on the article is likely to return gradually. There are still plenty of things to work on, starting by clearing out distracting bloat, like I did here. Dicklyon (talk) 22:52, 6 December 2014 (UTC)

Unending amazement, Dick. Here you are lamenting that Rashid's idealizations have shortcomings, and then deleting the most often referred to shortcoming of employing unilateral elements that ignore the complexities of all real feedback systems. Congrats. Brews ohare (talk) 03:37, 7 December 2014 (UTC)

The text I removed said "This circuit uses ideal unilateral elements," which was self-evident to those who know what it means, and cryptic to the general reader; and the cited source did not support or explain the assertion. It would not hurt to explain the unilateral model, and the limitation of its accuracy, but throwing it out in a figure caption this way was not helpful, nor was the citation. Dicklyon (talk) 04:28, 7 December 2014 (UTC)

Removal of links

Negative feedback amplifier with external disturbance.¹

In this edit Dicklyon removed the inspiration for this figure, namely:

¹Marc Thomson (2006). "Figure 11-4: Classical single input, single output control loop". Intuitive Analog Circuit Design. Newnes. ISBN 9780080478753.

Thompson's referenced figure includes the external disturbance D in the feedback loop in a simple manner analogous to this diagram, unlike many texts that use more elaborate figures. I believe it adds to the stability of WP articles if sources are provided, as future editors may dispute the adequacy of the diagram.

In addition, Dicklyon removed the subsequent sentence and accompanying source in the caption to the figure for the negative feedback amplifier that says:

"This circuit uses ideal unilateral elements.²"

²Wai-Kai Chen (2005). "Chapter 13: General feedback theory". Circuit Analysis and Feedback Amplifier Theory. CRC Press. p. 13–1. ISBN 9781420037272. [In a practical amplifier] the forward path may not be strictly unilateral, the feedback path is usually bilateral, and the input and output coupling networks are often complicated.

In more detail, the removed linked source says:

"The forward path may not be strictly unilateral, the feedback path is bilateral, and the input and output coupling networks are often complicated. Thus the ideal feedback model is not an adequate representation of a practical amplifier."

"We shall develop Bode's feedback theory, which is applicable to the general feedback configuration and avoids the necessity of identifying the transfer functions μ(s) and β(s)."

That is, this source points out that in real situations, the feedback path is bilateral, not unilateral as indicated in the figure, and the forward path (that is, via the open-loop amplifier) may not be unilateral (because of implicit feed-around, both forward and backward, found in many real-world amplifiers). Moreover, this over-idealization is so serious that this source has abandoned the use of this breakup of a system into a forward and a feedback path altogether, as described in the second quote from this source.

For those editors here who want more detail, two approaches to these issues are described in the articles Return ratio and Asymptotic gain model. For a few words of introduction, see Rahul Sarpeshkar. "Chapter 10: Return ratio analysis". Ultra Low Power Bioelectronics. and the Rosenstark and Choma methods are described in Gaetano Palumbo, Salvatore Pennisi. "§3.3 The Rosenstark Method and §3.4 The Choma Method". Feedback Amplifiers: Theory and Design. pp. 69 ff..

Of course, a more complete treatment of these real-world obstacles to the idealized amplifier diagram could be attempted, but removal of any indication at all that over-idealizations are present is a disservice to the reader. Brews ohare (talk) 14:39, 7 December 2014 (UTC)

Omission of these caveats can lead instability of the article because the figure can be challenged on these grounds as an over-idealization. An acknowledgement can defuse the situation in advance. Brews ohare (talk) 14:54, 7 December 2014 (UTC)

I'm glad you like Rahul Sarpeshkar's book. He gave me a copy a few years ago, and thanked me for my help and collaboration over the years; the book has a very nice acknowledgement, and references several of my papers including a couple that we did together, which involve feedback amplifiers. But I admit the return ratio approach is new to me. It would be a good idea for this article to mention and link it, but probably not in a caption where it's not needed. Dicklyon (talk) 18:01, 7 December 2014 (UTC)

Do you agree with a paragraph on inadequcies of the unilateral block diagram citing the 3 works already mentioned? Brews ohare (talk) 21:17, 7 December 2014 (UTC)

I'd have to see it. Depends on what you mean by "inadequacies". The unilateral block diagram is adequate for many things. Dicklyon (talk) 06:23, 8 December 2014 (UTC)

And how about the link to Thompson supporting the introduction of D in the diagram? Brews ohare (talk) 13:06, 8 December 2014 (UTC)

I see that the Thompson reference has been restored. I have contributed a few lines about the idealization of the diagram for your comment. Brews ohare (talk) 13:35, 8 December 2014 (UTC)

Suppression of sourcing

From this version of the sub-section on negative feedback amplifiers several notes were removed by Binksternet and then again by Dicklyon. The reason for removing these notes, according to Binksternet is:

this kind of argument inside references is best saved for the main article about the sub-topic

and Dicklyon's reversion is based upon the suggestion:

Please re-do it with nothing in ref tags except references.

Now, what exactly is in these notes that constitutes "an argument inside references" and why on earth should notes be restricted to citations only, without amplification of points raised? That restriction is not normal practice in books and articles. In any event, one of the removed notes is Dunn:

Peter Carroll Dunn (2000). Gateways into Electronics. John Wiley & Sons. p. 192. ISBN 9780471254485. Feedback circuits are mostly bilateral [...making...] feedback models at least awkward

which simply supports the assertions of the already included reference by Chen. Another of the removed sources is Gray and Meyer, the definitive text on this subject, cited to support the deleted remark that the more general methods are often easier to use:

Paul R Gray, Paul J Hurst, Stephen H Lewis, Robert G Meyer (2001). "§8.8 Feedback circuit analysis using return ratio". Analysis and design of analog integrated circuits (PDF) (4th ed.). John Wiley & Sons. p. 599. This alternative analysis, which is often easier than two-port analysis, is called return-ratio analysis.{{cite book}}: CS1 maint: multiple names: authors list (link)

These notes obviously involve no "argument" and are simply supplementary references to support the text. They contain quotes from the sources included simply for the benefit of those trying to find the relevant remarks made by these authors, and they say nothing at all that the WP text has not already said.

The third source removed is the well-regarded text by Jaeger:

Richard C Jaeger, Travis N Blalock (2004). "§18.7: Common errors in applying two-port feedback theory". Microelectronic circuit design (2nd ed.). McGraw=Hill Higher Education. pp. 1409 ff. ISBN 0072320990. Great care must be exercised in applying two-port theory to ensure that the amplifier feedback networks can actually be represented as two-ports

which is more technical than the text in its introduction of the idea of two-port analysis, although the reader who looks at this source will soon discover this is the traditional approach to the treatment of the unilateral block decomposition of the negative feedback amplifier. Jaeger is worth referencing because he points out very clearly the misleading nature of the unilateral block approach, which is the source of "common errors". (See also Hurst.) The reason for making this a note is, of course, to avoid interruption of the flow of the main WP text, which is the commonly accepted purpose for footnotes.

Removal of these three sources is contrary to one primary purpose of WP, namely to serve as a guide for readers to pertinent literature on a topic. Brews ohare (talk) 14:25, 18 December 2014 (UTC)

It's unclear why you think bloating up this tangent with more sources helps the article. Or why you'd introduce the topic of two-port networks in a footnote just to shoot it down. Dicklyon (talk) 16:37, 18 December 2014 (UTC)

Dick: I'm unclear why providing sources fits into the category of "bloating" or why indicating deficiencies in the primarily pedagogical unilateral block model used in the article is a "tangent". Perhaps you could address these two claims in more detail?

The topic of two-ports is incidental to the point being made, namely that the unilateral block approach lends itself to errors, some a bit subtle. That point supplements what is noted, that this approach is defective.

You have a desirable goal in keeping WP brief, but that can conflict with the goal of an accurate and adequate portrayal. Brews ohare (talk) 17:06, 18 December 2014 (UTC)

I believe you're confused. A two-port is not a unilateral model. The cited comparison involving that is somewhat off topic, comparing different ways to handle the more general case than can be described with traditional feedback concepts. We already have enough acknoledgement of the limitations, and links to more general techniques, so the extra stuff just looks like your usual bloating. Dicklyon (talk) 22:48, 18 December 2014 (UTC)

Once again the reasonable directives given at WP:SUMMARY are being ignored by Brews ohare. Let's not make this article the place to prove or disprove pet theories. The individual articles are the place for further detail. Binksternet (talk) 23:20, 18 December 2014 (UTC)

Dick: You're right that the general two-port can be bilateral. So the larger issue is that dividing the amplifier into a forward and a feedback block is inadequate, even though it is more general than when the blocks are made unilateral.

Binksternet: Of course it is true that breaking up articles into main articles and subsidiary articles can be a good thing. But then of course the main article should put the subsidiary articles in context, and in particular should give the reader of the main article enough guidance so they know that they would be well served by looking at the other articles. Removing a few citations hardly falls under WP:SUMMARY. Brews ohare (talk) 00:38, 19 December 2014 (UTC)

It is really insulting to have my inclusion of sources labeled by Binksternet as a personal "pet theory". Why are you choosing to be confrontational over a noncontroversial matter found in dozens of sources?

And Dick, the point you bring up that the unilateral block approach is inapplicable even when generalized to a two-block two-port break up suggests that this paragraph on limitations should be expanded to point out this more serious issue documented by Gray & Meyer and by Jaeger & Blalock. Brews ohare (talk) 03:15, 19 December 2014 (UTC)

An interesting quote

From Choma & Burgess §6.3 Circuit Partitioning:

"From a purely computational perspective, the preceding section of material is useful for determining the steady-state performance, transient time-domain performance, sensitivity, and stability of practical feedback networks. But from the viewpoint of circuit design, the practicality of the subject material might logically be viewed as dubious, for it promulgates results that depend on unambiguous definitions of the open loop gain and feedback factor. Stated more directly, the results of Section (6.2) are useful only insofar as the transfer function of interest for a given circuit can be framed in the block diagram architecture of Figure 6.1. [The diagram in the WP subsection] Unfortunately, casting a circuit transfer function into the form of Figure 6.1 is a non-trivial task for at least three reasons.

First, neither the open loop amplifier nor the feedback function conducts signals unilaterally. This is to say that amplifiers, and especially amplifiers operated at high signal frequencies, invariably have intrinsic feedback. Moreover, since the feedback sub-circuit is generally a passive network, it is clearly capable of conducting signals from circuit input to circuit output ports, as well as from output to input ports.

Second, the open loop amplifier function is not completely independent of the parameters of the feedback subcircuit, which invariably imposes impedance loads on the amplifier input and output ports.

Third, Figure 6.1 pertains only to global feedback structures. But practical feedback circuits may exploit local feedback; that is, feedback imposed between any two amplifier ports that are not necessarily the output and input ports of the considered system. Local feedback is often invoked purposefully in broadband analog signal processing applications. On the other hand, parasitic local feedback is commonly encountered in high-frequency systems because of energy storage parasitics associated with proximate on-chip signal lines, bond wire interconnects and packaging.

Fortunately, theoretical techniques advanced originally by Kron [21,22] exist to address this engineering dilemma. As is illustrated below, these techniques, which are now embodied into modern circuit partitioning theory [23], have been shown to be especially utilitarian in feedback circuit applications [24]."

[21] G. Kron, Tensor Analysis of Networks. New York: John Wiley & Sons, 1939.

[22] G. Kron, “A set of principles to interconnect the solutions of physical systems”, Journal of Applied Physics, vol. 24, pp. 965–980, August 1953.

[23] R. A. Rohrer, “Circuit partitioning simplified”, IEEE Transactions on Circuits and Systems, vol. 35, pp. 2–5, January 1988.

[24] J. Choma, Jr., “Signal flow analysis of feedback networks”, IEEE Transactions on Circuits and Systems, vol. CAS-37, pp. 455–463, April 1990

Brews ohare (talk) 17:42, 20 December 2014 (UTC)

Choma and Burgess say "casting a circuit transfer function into the form of Figure 6.1 is a non-trivial task" but in fact it can prove impossible. Brews ohare (talk) 17:46, 20 December 2014 (UTC)

There it is. Since nobody is disputing any of that, we can agree to agree. What's your point? Dicklyon (talk) 20:27, 20 December 2014 (UTC)

See point 3 in list of points in previous thread. Brews ohare (talk) 01:44, 21 December 2014 (UTC)

Which in the previous thread you still fail to clarify, and which has unknown relationship to this thread. Dicklyon (talk) 01:53, 21 December 2014 (UTC)

They key point in Choma's list of problems with the two two-port approach in the above quote is the distinction between local and global feedback. This distinction also is pointed out by Palumbo & Pennisi. Where local feedback is employed, a break-up of the feedback amplifier into a forward two-port block and a return feedback two-port block is, as Choma puts it "difficult, if not impossible".

The pertinence of this point to the formulation of the article is obvious to me - the division of the amplifier into these two blocks is applicable only to particular cases, even if the blocks are generalized from unilateral blocks to bilateral two-port blocks.

Can you agree that this point indicates a limitation of the WP treatment using the diagram? And that such a limitation should be pointed out as a caution to the reader that there is more to this topic, and that more general approach can be found in Jaeger, in Gray & Meyer, in Choma & Chen, in Palumbo & Pennisi and elsewhere? Brews ohare (talk) 03:06, 21 December 2014 (UTC)

Choma seems to be saying "not impossible", yet you are concluding the opposite? Or am I missing something? Dicklyon (talk) 03:15, 21 December 2014 (UTC)

The phrase "daunting, if not impossible" can be taken as "daunting, perhaps even impossible", or as "daunting, though perhaps not impossible". Inasmuch as we have examples where so far no two two-port representation has been found, it's all a bit moot. Few will see much future in trying to try to prove a particular example is impossible. What they will do after a few tries is to move on to other faster methods where there is no need for two two-ports. Brews ohare (talk) 04:43, 21 December 2014 (UTC)

Proposed final paragraph

The last paragraph of the subsection on the negative feedback amplifier reads:

Although the diagram illustrates the principles of the negative feedback amplifier, modeling a real amplifier as a unilateral forward amplification block and a unilateral feedback block is sometimes inadequate in practice.¹ Methods of analysis that do not make these idealizations have been developed,² and they are often easier to use.³ For details the interested reader can consult the articles Return ratio and Asymptotic gain model.

Notes

¹ Wai-Kai Chen (2005). "Chapter 13: General feedback theory". Circuit Analysis and Feedback Amplifier Theory. CRC Press. p. 13–1. ISBN 9781420037272. [In a practical amplifier] the forward path may not be strictly unilateral, the feedback path is usually bilateral, and the input and output coupling networks are often complicated.

² For an introduction, see Rahul Sarpeshkar (2010). "Chapter 10: Return ratio analysis". Ultra Low Power Bioelectronics: Fundamentals, Biomedical Applications, and Bio-Inspired Systems. Cambridge University Press. pp. 240 ff. ISBN 9781139485234.. The Rosenstark and Choma methods are described in Gaetano Palumbo, Salvatore Pennisi (2002). "§3.3 The Rosenstark Method and §3.4 The Choma Method". Feedback Amplifiers: Theory and Design. Springer Science & Business Media. pp. 69 ff. ISBN 9780792376439..

³ Paul R Gray, Paul J Hurst, Stephen H Lewis, Robert G Meyer (2001). "§8.8 Feedback circuit analysis using return ratio". Analysis and design of analog integrated circuits (PDF) (4th ed.). John Wiley & Sons. p. 599. This alternative analysis, which is often easier than two-port analysis, is called return-ratio analysis.{{cite book}}: CS1 maint: multiple names: authors list (link)

This paragraph seems to suggest that the difficulty with the idealized model is entirely due to the forward and feedback blocks being unilateral. However, the problem is more than that because, as pointed out by Dicklyon, the problem remains even if the blocks are made bilateral by representing them as two-ports. This issue is documented by Gray & Meyer and by Jaeger & Blalock. The addition of a sentence to this effect provides a clearer statement of the issues with the simple block representation of the negative feedback amplifier. A possible replacement for this last paragraph is the following:

Although the diagram illustrates the principles of the negative feedback amplifier, modeling a real amplifier as a unilateral forward amplification block and a unilateral feedback block is sometimes inadequate in practice.¹ In fact, the issue is not just the unilateral nature of the blocks, and breaking up the amplifier into forward and feedback blocks using bilateral two-port networks also is restricted in practice.² Methods of analysis that do not make these idealizations have been developed,³ and they are often easier to use.⁴ For details the interested reader can consult the articles Return ratio, Asymptotic gain model, and Extra element theorem.

Notes

¹ Wai-Kai Chen (2005). "Chapter 13: General feedback theory". Circuit Analysis and Feedback Amplifier Theory. CRC Press. p. 13–1. ISBN 9781420037272. [In a practical amplifier] the forward path may not be strictly unilateral, the feedback path is usually bilateral, and the input and output coupling networks are often complicated.

²Richard C Jaeger, Travis N Blalock (2004). "§18.7: Common errors in applying two-port feedback theory". Microelectronic circuit design (2nd ed.). McGraw=Hill Higher Education. pp. 1409 ff. ISBN 0072320990. Great care must be exercised in applying two-port theory to ensure that the amplifier feedback networks can actually be represented as two-ports

³ For an introduction, see Rahul Sarpeshkar (2010). "Chapter 10: Return ratio analysis". Ultra Low Power Bioelectronics: Fundamentals, Biomedical Applications, and Bio-Inspired Systems. Cambridge University Press. pp. 240 ff. ISBN 9781139485234.. The Rosenstark and Choma methods are described in Gaetano Palumbo, Salvatore Pennisi (2002). "§3.3 The Rosenstark Method and §3.4 The Choma Method". Feedback Amplifiers: Theory and Design. Springer Science & Business Media. pp. 69 ff. ISBN 9780792376439.

⁴ Paul R Gray, Paul J Hurst, Stephen H Lewis, Robert G Meyer (2001). "§8.8 Feedback circuit analysis using return ratio". Analysis and design of analog integrated circuits (PDF) (4th ed.). John Wiley & Sons. p. 599. This alternative analysis, which is often easier than two-port analysis, is called return-ratio analysis.{{cite book}}: CS1 maint: multiple names: authors list (link)

I believe this added sentence and source makes the situation clear and leads the reader to sources that explain the matter carefully. Brews ohare (talk) 15:13, 19 December 2014 (UTC)

I would be interested in knowing what this means: "In fact, the issue is not just the unilateral nature of the blocks, and breaking up the amplifier into forward and feedback blocks using bilateral two-port networks also is restricted in practice." What does "the issue" refer to? What does the source say about this other than "Great care must be exercised in applying two-port theory to ensure that the amplifier feedback networks can actually be represented as two-ports", which sounds like a tautology? What does this matter here? I think it doesn't. Dicklyon (talk) 19:01, 19 December 2014 (UTC)

Dick: "The issue" is the adequacy of the representation of the negative feedback amplifier in the provided diagram as two unilateral blocks. Jaeger, as also is the case with every text I know, discusses at length the representation of the negative feedback amplifier using a more general representation as two bilateral blocks: a two-port network for the forward amplifier block and another two-port for the feedback network. I imagine you are familiar with these discussions. Jaeger then points out in the referenced section that in some very mundane examples the port conditions are not satisfied, so what appears topologically to be a two-port is not electrically a two port. If the erroneous assumption that one has a two port is used, incorrect assessments will result for effect of feedback upon the amplifier. The admonition is not a tautology but a word of warning that this error is easy to make. That is one reason the return-ratio approach is better. Why does this matter here? First, it matters that the diagram forming the basis of the discussion is an oversimplified case. Second, as is often said, one reason is that it uses unilateral blocks. Third, as Jaeger points out, even if these blocks are not unilateral, but bilateral (as often is suggested as a cure), the diagram still is a simplified case. Fourth, better approaches (return-ratio, for instance) are available, and of practical importance. The addition of one sentence with a reputable source is hardly a digression adding "bloat" to this short paragraph. Brews ohare (talk) 20:37, 19 December 2014 (UTC)

I'm not sure I agree that the different sources you cite are about that issue. One is talking how two ports might not be the easiest way. The other is saying they may not be adequate, but you haven't told us enough of what it says to give a clue why. I suspect it's about nonlinearity, which is a whole different issue. Anyway, I don't find your added text adds anything useful. Dicklyon (talk) 02:06, 20 December 2014 (UTC)

Dick: I gather that assuming everything I have said is 100% what the sources say, you still opine that the added sentence contributes nothing. If you can explain that point, I'll delve into your uncertainty about whether I can read. The logic is as follows:

1. The diagram is an idealization that does not apply to many practical cases (Chen)

2. One idealization in the diagram is the use of unilateral blocks, which ignores the bilateral nature of many feedback networks. (Chen)

3. A different idealization that uses bilateral blocks also does not apply to some common examples. In other words, the unilateral issue commonly identified as the problem is not the whole story behind the inadequacy of the diagram. (Jaeger)

4. More general approaches are needed, and they exist, that don't use the two-block division. (Sarpeshkar, Gray and Meyer, Palumbo & Pennesi)

Item 3 is what has been added. The rest is there already. Now, item 3 does add to the picture, pointing out that the unilateral issue isn't the point; it is the indivisibility: splitting a feedback amplifier up into a forward two-port and a feedback two-port (bilateral or unilateral) is not always feasible, failing even for some simple examples. This problem exists even for entirely linear (e.g. small-signal) circuit elements. If you continue to doubt that even after looking at these sources and perhaps the WP article discussion here, please elaborate. I will dig up even more sources that will add to your reading to-do list. Brews ohare (talk) 03:01, 20 December 2014 (UTC)

That's just great, taking your argument into main article space. At least it's not as much a disgression there, though it still looks like bloat for the purpose of conversation and argument more than to help the reader. Dicklyon (talk) 20:32, 20 December 2014 (UTC)

I believe you still haven't told us what Jaeger says that implies sometimes a two-port analysis will not work. The quote just says one must be careful to not make mistakes. Dicklyon (talk) 20:37, 20 December 2014 (UTC)

I'll outline what Jaeger does, but the same point is made in all the sources above:

"Many popular textbooks incorrectly apply the feedback theory to these amplifiers because a simple relationship seems to relate the output current to the feedback current. The best way to illustrate the problem is through an example that produces erroneous results."

He then discusses a series-series amplifier and a shunt-series amplifier, in both of which an apparently natural choice for the feedback two-port leads to wrong results. He is forced to use a full-blown mesh analysis to get the right answers, and then verifies the mesh analysis by computer simulation. He traces the error with the two two-port analysis to the fact that the feedback two-ports in both examples are not two-ports despite having two input and two output leads.

Now, he hasn't proved impossibility, but only a trap. He also has shown that to set up a two two-port version in both thee examples is, as Choma says, daunting, if not impossible.

It is perfectly clear that the consensus among authors is that in such cases where the two two-port approach proves intractable, to duck the complexity of a mesh analysis the expedient approach is to use the Rosenstock or the Choma methods. One cannot prove definitively that a given circuit falls into the "impossible" category, but when faced with a recalcitrant circuit that might actually be impossible, the best approach is not to spend an inordinate amount of time beating one's head on the wall, but to use other methods.

The added sentence that you have removed does not make exaggerated claims; all it says is:

" In fact, the issue is not just the unilateral nature of the blocks, and breaking up the amplifier into forward and feedback blocks using bilateral two-port networks also is restricted in practice.^Jaeger

The point is that the diagram is not generally useful and its lack of utility is not due to the unilateral choice of blocks, but is more fundamental: some negative feedback amplifiers cannot be fit into this picture, or at least have defied all attempts so far to do so. What is your objection? Brews ohare (talk) 03:43, 21 December 2014 (UTC)

My objection is that you keep making up weird conclusions, like that last one. We already acknowledge, don't we, that other methods are sometimes needed, and we link to them, right? I still don't see the sources concluding that the two-port method is impossible, which is what you seem to be concluding. No need to get into that question here, as the point is too subtle for the audience of this article. You can get into details in Negative feedback amplifier. Dicklyon (talk) 04:14, 21 December 2014 (UTC)

Dick: The reverted sentence says nothing about impossibility. It says the issue of unilateral blocks isn't the only objection, because division into bilateral two ports also has problems. Brews ohare (talk) 04:35, 21 December 2014 (UTC)

I disagree with that conclusion. But the article already has references to the other methods, so why push an intermediate marginal conclusion into it? Dicklyon (talk) 04:39, 21 December 2014 (UTC)

I doubt that you disagree that the diagram is inadequate to describe all negative feedback amplifiers. It is hard to see why the reader would not ask: Well what's the matter? Your answer is: "Don't worry about it - there are other ways to do it." A more complete answer is: "One issue is the use of unilateral blocks that can't describe real circuits, Although the diagram works better with bilateral blocks like two-ports, that approach proves complicated and sometimes fails too. Often other methods that don't use such diagrams prove less frustrating and less liable to error."

Dick, the more complete answer you reverted takes only one short added sentence and provides a source that could be helpful for a reader wondering about what is wrong here. Could it be that your interest in having your way is taking precedence over helping the reader? Brews ohare (talk) 05:32, 21 December 2014 (UTC)

I quit

OK, having heard the explanation, and the accusation of bad faith, I'm just going to withdraw and let Brews work it out with the other editors. If they are convinced by now with all the explanation, I won't interfere. Dicklyon (talk) 05:44, 21 December 2014 (UTC)

Dick: Refusing any direct response to the issues raised, what choice do you have? Brews ohare (talk) 06:19, 21 December 2014 (UTC)

You have chosen to phrase the issue as some never-proposed thesis that it is impossible to model a negative feedback amplifier as two blocks, when what is said is that such a depiction is subject to caveats, and states the caveats with a source. It is an old trick where the goal is to win a debate and not to further understanding, to set up a strawman position and knock it down, avoiding engagement. Brews ohare (talk) 16:38, 21 December 2014 (UTC)

Brews ohare, you method is to wear down the opposition with continual pointless arguments, another old trick. You are ignoring the bigger picture which is the reader. The additions you wish to make are not helping the reader understand the topic. Keep it simple here. Put extra detail on the sub-article pages. Binksternet (talk) 16:58, 21 December 2014 (UTC)

Binksternet: It is interesting that you think I am engaged in "wearing down" Dicklyon. That view possibly extends from observing the length of this exchange without regard for its content. The basic point is the addition (or not) of a single sourced sentence to the text. Dicklyon's opposition is that it says nothing useful because the existence of other methods has been mentioned. Your view is not that it says nothing, but that it is too much detail in a general article.

Neither of you attempt to support these opposite opinions of yours that are nothing more than a personal bias toward brevity, even at the cost of clarity. A more useful discussion would focus on how to better inform a reader about how to find a more complete idea of the limitations of the diagram that is the basis for the WP description. What is wearing is unending unsupported repetition of personal taste without concern for informing the reader. Brews ohare (talk) 17:54, 21 December 2014 (UTC)

To avoid these squabbles, we can just note the issue and dispatch the Negative feedback amplifierj, where details are more appropriate. Done. Dicklyon (talk) 18:28, 23 December 2014 (UTC)

Signal flow graphs

A simple negative feedback system employing two unilateral blocks

Possible signal-flow graph for the asymptotic gain model

In this edit Dicklyon removed the remark:

Methods of analysis based upon signal-flow analysis that do not make these idealizations have been developed, and are discussed in various articles, for example, Return ratio, Asymptotic gain model, Extra element theorem and Negative feedback amplifier.

with the one-line edit summary These uncommented additions don't even make sense, since signal flow grpahs are inherently unidirectional.

Aside from the demeaning tenor of this comment claiming that the removed material doesn't 'even' make sense, this comment includes the irrelevant remark that "signal flow graphs are inherently unidirectional" suggesting, I suppose, that the criticism of the ideal block diagram that it is oversimplified because of its unidirectional nature applies equally to disqualify signal-flow graphs, which because of their unidirectionality also must be viewed as too idealized.

If this is indeed Dicklyon's intention, it is mistaken.

The signal-flow graph, as described in the article Asymptotic gain model is "useful because it completely characterizes feedback amplifiers, including loading effects and the bilateral properties of amplifiers and feedback networks." Moreover, the greater generality of signal flow graphs is the subject of the very well known paper critiquing both the unidirectional and the two-port two-block approaches to amplifiers: J. Choma, Jr. (April 1990). "Signal flow analysis of feedback networks". IEEE Transactions on Circuits and Systems. CAS-37: 455–463. (On-line here) and as he also comments in the quote above. Similar views are stated by Wai-Kai Chen:

"The third method of feedback circuit analysis exploits Mason's signal flow theory. The circuit level application of this theory suffers few of the shortcomings indigenous to block diagram and two-port methods of feedback circuit analysis. Signal flow analysis applied to feedback networks efficiently express I/O transfer functions, driving point impedance, and driving-point output impedances..."

Inasmuch as two-port block analysis involves bilateral information flow, signal flow graphs are capable of incorporating these effects as well, simply by including arrows that incorporate both directions of flow. Further discussion can be found in Palumbo & Pennisi.

Of course, Dicklyon is entitled to misunderstandings (although they would be cleared up if he chose to read the references provided repeatedly here), but with more humility (or with greater regard for sourcing his opinions) he would not trumpet his gut instincts as if they were decrees from Olympus or perhaps special insights gleaned on Mount Sinai. Brews ohare (talk) 16:29, 29 December 2014 (UTC)

The removed links Return ratio, Asymptotic gain model, Extra element theorem, and the removed perspective that the signal-flow analysis is more general than the unilateral (or bilateral for that matter) two-block diagram both reduce the value of this article in guiding the reader to what WP contains. Brews ohare (talk) 17:04, 29 December 2014 (UTC)

The signal flow graph is an interconnection of unidirectional blocks and summing junctions. I understand your points about why that can be a good approach. The Negative feedback amplifier article would be a good place to introduce this material. I removed the distraction about two-ports to make a cleaner linkage. Dicklyon (talk) 06:30, 30 December 2014 (UTC)

Dick, this is not an introduction to this material - it is guidance for the reader so they can find such an introduction elsewhere, and it is is spread over several articles, and is not discussed in the article Negative feedback amplifier. The reader also needs enough information to understand why they might find these other articles of interest, especially if they are new to the subject. Brews ohare (talk) 06:34, 30 December 2014 (UTC)

I'm saying that if you need to discuss it, then Negative feedback amplifier would be a much more appropriate place. Why would you introduce it here, and not there? Dicklyon (talk) 06:41, 30 December 2014 (UTC)

Dick, although it might be sensible to have a discussion of signal-flow approaches to the amplifier in the article Negative feedback amplifier, at the moment that is not the situation. Instead we have many articles like Return ratio, Asymptotic gain model, Blackman's theorem where signal flow analysis is applied to particular aspects of feedback amplifiers. So, until matters change in WP coverage, the reader is served by pointing out the relevance of these articles for their consideration. Simply providing no indication of what is up, and referring the reader to negative feedback amplifier, where these topics are in fact not discussed but referred again to other articles, gives the reader of Negative feedback no idea of the nature of the oversimplifications made in this subsection, or if they are something the reader might (or might not) find interesting. That guidance takes exactly one sentence, yet you consider it 'bloat'.

Dick, you no longer argue that this added guidance to the reader doesn't even make sense. You simply object to assisting readers to find their way around in WP. Is that advisable? Why should your personal penchant for brevity prevail over WP objectives? Brews ohare (talk) 15:04, 30 December 2014 (UTC)

Repeated refusal to guide the reader

This talk page is replete with editor suppression of single-sentence additions to this article that say how other WP articles may be relevant to a reader interested in negative feedback. The reason given for this opposition is not that the provided sources and links are incorrect or misleading, but that even one-sentence guidance to other WP articles is 'bloat' that unnecessarily lengthens the article. It is patently ridiculous to suggest that WP articles cannot support short links to other WP articles relevant to a topic, or citations to sources where details can be found, and portraying such a single sentence addition as a 'discussion' best moved to a specialized article is, shall we say, gross distortion.

I fail to see how this radical insistence upon elimination of single-sentence guidance with WP links to other WP articles serves WP or its readers, or how this penchant for brevity is anything but imposition of a personal aesthetic, unsupported by WP policy or guidelines. Brews ohare (talk) 18:14, 30 December 2014 (UTC)

You do not understand how Wikipedia works. Articles are connected primarily by inline wikilinks. It's how a wiki works. In particular it is how this wiki works. Articles can be linked in other ways but this is exceptional and not part of the article content. And article might have links in a see also section. It might have a navbox or infobox with links. It might be written in summary style with short sections with {{main}} links to other articles. But it needs none of these, and there are many good and probably featured articles with none. An article does need inline wikilinks, and these are the primary, and should be the only way within content, of linking to other articles.

So write the article so it describes the topic. Then where possible link to other articles, not too many so only to relevant articles, usually only once at the first mention. Never refer to articles directly as you were doing. In particular don't write "Wikipedia articles" (or "Wikipedia" anything except in its own article) as it makes no sense when articles are mirrored on other encyclopaedias.--JohnBlackburne^words_deeds 00:53, 31 December 2014 (UTC)

Blackburne, I don't understand your comment. For one example, what is going on here is in-line linkage to other WP articles as you seem to recommend, for example, to signal flow graph as it pertains to negative feedback and is described in return ratio, asymptotic gain model, Blackman's theorem, Extra element theorem and so forth, whose mere linkage as a heads up to the reader is objected to by Dicklyon as unwarranted digression. Perhaps you could explain specifically what is objectionable about the reverted sentence containing these links? I think it is helpful to a reader to be told that the presented discussion is over-simple and more complete methods are described in these other WP articles. There is no attempt to go into detail, just links with a few words to help the reader decide whether they could fit their interests. Brews ohare (talk) 02:03, 31 December 2014 (UTC)

I know you don't understand it, that's clear from your editing. I'm sorry if my further explanation doesn't help. Here is the WP content guideline on such references: Wikipedia:Manual of Style/Self-references to avoid.--JohnBlackburne^words_deeds 02:12, 31 December 2014 (UTC)

Blackburne: Just love your collegiate tone! However, your link to using WP to self-reference its own validity indicates a misunderstanding of the issue here. The reference to the article Return ratio, for example, is not a use of WP to support its own take on the subject in lieu of published sources, but is only a heads-up to the reader that there is more on WP concerning approaches to the negative feedback amplifier. As support (a different matter than just a flag or a 'table-of-contents' thing) sources are cited like Choma, Chen, Palumbo, etc. (see above).

If you were to read and refer directly to the removed material instead of working on hypothetical abstract assumptions that are divorced entirely from concrete instance, confusion due to your erroneous conception of the issues would not occur. Brews ohare (talk) 03:16, 31 December 2014 (UTC)

"use of criticism and punishment"

   The phrase "positive criticism" is seldom enuf discussed (literary criticism being the most often heard exception) that the unmodified noun is often misunderstood as excluding the positive and neutral functions". ....
--Jerzy•t 19:55, 4 November 2018 (UTC)