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is external linking allowed?, in any case much good info in http://prof.usb.ve/williamc/Mejoramiento/historia.html should be made available here
in electronics the para are disordered, positive feedback (suject of great Armstrong deForset patent dispute)predates Black's negative feedback amplifier and should be refered to first, PID is a subset of negative feedback control techniques :jcox
--- I don't believe that the explanation of audio feedback is correct. It identifies the frequency of feedback noise as related to the transit time through the system (Implying it's a matter of repeating the waveform, the effect you might get with digital echo or flange). But I'm 95% sure that's completely irrelevant in a system like this, the waveform is completely obliterated by all the transitions made, all you're left with is frequencies that approximate those you started with.
OK, a quick test: I was able to get audible feedback with a 1/2 second delay in the loop, which should give a frequency of 2 hz, 5 octaves below audible.
So I'm rather sure the frequency of feedback is not determined by transit time, but by the frequency response of the whole system. All real world systems contain some capacitance and inductance, meaning they all act as very wide, low, bandpass filters. But when you amplify and feedback the filtered sound into the filtered sound, you've naturally created an oscillator (the simplest forms of analog oscillators work on exactly this principle).
So unless anyone objects I'm going to change the explanation to reflect this. User:Wji
Although feedback was perhaps discovered during the course of the development of electronics, it exists in many natural processes and the word (although not present in earlier dictionaries, for example the original OED) represents a concept in general use outside engineering. Therefore the article should begin with the general concept but include a substantial section on control theory. I was first introduced to feedback during training on servo mechanisms many years ago and am a bit rusty, but I clearly remember it took both positive and negative feedback to make them work. What we call feedback like with a microphone is perhaps not feedback in the sense we are using it here. User:Fredbauder
I agree that there is more than one sense of the word feedback. The Penguin Dictionary of Electronics, for example, has separate entries for feedback in the general sense and feedback control loop in the specific context of control systems. The Chambers Science and Technology Dictionary has headings for feedback (acoustic), feedback (telecommunications) and feedback control loop, so perhaps there are really three different concepts. If we wish to separate the general from the particular, I would suggest the following structure for the Wikipedia (with separate articles for hunting and feedback):
Do you think this is reasonable? Unfortunately it contradicts your idea of putting the natural phenomena first. My scheme lists things in the order of discovery by man, whereas yours is nature-based. I cannot say which is better.
As for the microphone example, this is an illustration of feedback in the electronic (or electroacoustic) sense, not in the control loop sense. The feedback is always positive, because sound from the loudspeakers is always added to, never subtracted from, the sound entering the microphone. What changes is the loop gain, which varies as the user moves the microphone relative to the speakers. As soon as the loop gain exceeds unity, the system howls. This effect is independent of frequency. I believe that a system with negative feedback can only become unstable if the signal frequency exceeds the bandwidth of the feedback loop.
In control theory you can have multiple feedback paths (often three: proportional, integral and derivative) and it is meaningless to talk about overall positive or negative feedback, because the three paths may have different characteristics. -- Heron
What I suggest is a simple introduction which includes the general case, followed by as much specialized technical information as you feel appropriate. I agree the notion of postive and negative is applicable only to 2 dimensional systems, but I think it should remain in the introduction. I don't think organization around order of discovery is good; I prefer organization to start with a brief general introduction using simple language and concepts followed by (in this case) an engineering section, followed by the ways the concept has been adapted to natural systems. I guess runaway positive feedback is what we are talking about with apmplifiers. Fred Bauder
I divided the article into sections, without changing the words much. I may go further and remove the acoustic example to a separate article, but I'll leave 'hunting' where it is. -- Heron
I have been bold and removed the acoustic feedback section totally. I have linked the existing article at Audio feedback to the disambiguation page. The main differences in the removed section (reproduced below) lacking in the original page are the points about the band-pass filter and the electronic oscillator.
I believe the band-pass filter point is incorrect anyway. True, all systems have some kind low and high pass filter in them, but this is generally well outside the human range of hearing, and in any case, makes no difference to the presence of feedback. The deleted section was also vague as to whether this was affecting the presence or nature of the feedback, but if it were just the latter, there are plenty of other factors involved (at the very least, the inherant EQ of the system would be much more important).
Also, the electronic oscillator point seems slightly amibiguous too, although I could understand if people wanted this link in the main article. It might be worth pointing out that the simplicity is certainly not in the waveform, but in the construction. -- postglock 07:49, 6 Jun 2005 (UTC)
Main article: Audio feedback.
A well-known example of runaway positive feedback in electronic systems is called "howl" or "howl-round". This occurs in public address systems when sound from the loudspeakers reaches the microphone, is amplified by the system, and is then fed back into the system at even higher volume. All electrical systems contain capacitance and inductance and so act as band-pass filters responding better to certain frequencies. In a single loop through the system, this effect is negligible, but it becomes severe when the signal passes through the system repeatedly. This effect is the basis of the simplest kinds of analogue electronic oscillator.
postglock- lemme know if my last version works for you. thankz, Ished-out amounts of Vonn-ness 14:19, 10 September 2005 (UTC)
> Feedback is the signal that is looped back to control a system within itself.
The mention of "signal" and "control" seem overly teleological. Here are some definitions of feedback loop from around the net; a definition of feedback ought to work well with these sorts of definitions:
What is your favorite, least constraining definition of feedback?
love, raiph 05:11, 10 October 2006 (UTC)
There's a long laundry list of important theories, phenomena and more built directly on top of feedback loops that aren't mentioned on this page but should, imo, be considered. (I think I could easily list a dozen, and maybe a hundred, but the specifics aren't my point and I really don't want to get into that game yet if we can avoid it.)
Conversely, much of what's on the page right now seems too detailed, even for me, someone who's been intellectually focused on feedback loops for over a decade.
I propose I/we refactor the page. The introduction should be as general as possible. A History section seems a natural. Maybe an Examples section. I see most of the details of particular feedback phenomena going on their own pages.
Comments?
love, raiph 03:44, 3 October 2006 (UTC)
I am used to finding concise explanations in the first paragraphs of a Wikipedia article, and would propose the following thumbnail sketch of "feedback" for the first para. I haven't edited an article so won't presume, but this example is technically accurate and memorable:
Feedback: an action changes a system and then the system changes the action.
Positive feedback increases the action: you step on the brake pedal in a moving car, and the car slows, pushing your foot down harder on the brake.
Negative feedback decreases the action: you step on the gas pedal and the car accelerates, pulling your foot off the gas pedal.
If this is appropriate perhaps someone will include it.
68.98.117.241 23:25, 27 January 2007 (UTC)
I agree with the above change, and suggest that the current definitions in Types of Feedback are in fact incorrect and misleading. An example of negative feedback is a thermostat heating a room that is too cold. This is not reducing output, but increasing output (from the heater) or increasing input (into the room).
I also feel that the "bipolar feedback" definition is confusing - both positive and negative feedback mechanisms can cause output to change in either direction, so both are bipolar. But feedback can't be positive and negative at the same time.
Finally, hunting is more correctly a case of over-control, where a negative feedback signal overshoots the mark. This is a type of oscillation, but doesn't strictly involve positive feedback at all.
I suggest that this article could benefit from better clarity of the terms positive and negative earlier on. I had started to edit, but realized that my background (electronics) is probably too narrow for a general article.
Trevithj (
talk) 20:56, 18 August 2008 (UTC)
There is a Rush album called Feedback that should be included in the disambiguation page. -- The Fwanksta
A splitting of the article has been proposed on 15 March 2007. Nobody made any suggestions about this untill I yesterday removed the splitting tag. Now today User:Intgr reversed this with the argument:
Now I think there are at least four good reasons not to split:
I think this article is only in need of an expert, who creates a more general introduction, which shows how all these aspects are related to one central concept. For example this article is comparable with the complexity article. This is also one paradigm, with different applications in the disciplines. - Mdd 18:53, 28 August 2007 (UTC)
Their is no need to spread so related knowledge over a number of small articles - Mdd 05:49, 29 August 2007 (UTC)
Their are more arguments agains spliting the article:
I also think that:
Now I think I look at the concept of feed back from a kind of fundamental "systems science point of view". In this perspective the control theory aspect is not whole separate aspects beside e.g. biological, economical, electronical, ergonomic and mechanical forms of feed back. The control theory aspects with their mathematical forms of representation are the fundamentals for all kind of specialized applications.
I do agree something has to be done with this article. In it's current form it's just a collection of seemingly unrelated facts. I'll see if I can improve this a little. - Mdd 20:14, 7 September 2007 (UTC)
I removed the tag to split the article because there was no response the last four weeks. - Mdd 19:59, 12 November 2007 (UTC)
Hello. This article has two references, which is good. I added a "citations missing" tag because most sections have no inline citations and thus there is no way for the reader to know to which of the two refs any particular piece of information is sourced. OK in advance from my point of view to remove or move or change this tag. Best wishes. - Susanlesch 18:43, 12 November 2007 (UTC)
The example of vacuum advance control in older automotive ignition systems is bogus. Such systems did not employ any kind of feedback mechanism; i.e., they did not sense or react to any change they produced. —Preceding unsigned comment added by 24.22.7.221 ( talk) 21:31, 17 January 2008 (UTC)
The overview starts with the following sentence:
both is followed by three items instead of two. Hence, both should be removed. [ Georg] —Preceding unsigned comment added by 206.113.192.12 ( talk) 17:04, 25 January 2008 (UTC)
This seems confusing. How can feedback be both positive and negative at the same time? These are exclusive, surely. If this means a switching function, where the feedback changes between positive and negative, then the definition should clarify this. If it means a balancing, then two feedback loops must be involved (one positive, one negative.)
I have searched several online sources, and they all seem to cite each other (including this one) but I can't find an original definition. I have noted several references to "bipolar feedback transistors", but suspect that means a feedback loop involving a bipolar transistor, rather than "bipolar feedback" involving a transistor.
If bipolar feedback is present in many systems, can someone provide an example?
Trevithj (
talk) 02:43, 10 September 2008 (UTC)
I suggest that the primary purpose of the "Types of feedback" section is to distinguish negative feedback from positive feedback and outline other commonly used terms for types of feedback. This section should not get bogged down into fine details. The material that discusses the history of negative feedback should be moved into the Negative Feedback article. 203.206.220.108 ( talk) 00:44, 8 November 2008 (UTC)
The subsection "In electronic engineering" re-explains the concepts of negative feedback and positive feedback, which are not particularly specific to electronic engineering. Anyway, the section that contains this subsection is "Applications" so this is not the right place for explaining a general principle. 203.206.220.108 ( talk) 01:28, 8 November 2008 (UTC)
- 3 - the feedback signal does not change when the input signal changes, in which case there is no feedback. This is known as a Linear system.
If no feedback is an example of feedback then sitting on your bum is an example of flying. In addition linear systems can have feedback, and non-linear systems do not require feedback. Thus the above should be deleted. 203.206.220.108 ( talk) 12:31, 28 December 2009 (UTC)
This article has the same naming problem that correlation article had years ago. People at first mislabeled correlation as positive and negative. That is nebulous. It was correctly changed to direct and inverse correlation.
This article suffers from the same issue. It should NOT be positive and negative feedback. Instead the proper more accurate terms are converging and expanding feedback. The article needs renamed as well.
173.188.7.24 ( talk) 21:19, 4 March 2012 (UTC)
If no objection I would like to insert the below cited definition into the preamble, just above "feedback is also a synonym for...":
I hesitate only because the definition comes from the Behavioral Sciences, and may not be broadly applicable. Although it looks pretty good to me. -- Trevithj ( talk) 22:04, 15 March 2012 (UTC)
Above changes made, and also modified the synonym "feedback signal", since this definition makes that (old) distinction unnecessary/redundant. -- Trevithj ( talk) 05:51, 29 March 2012 (UTC)
As a suggestion, I would like to add a lead to the Types of Feedback section ... something like this:
-- Trevithj ( talk) 20:48, 22 March 2012 (UTC)
I see a need to make this section:
I propose: describing the history of the term "feed-back", and show its adoption from verb phrase to noun; moving the examples to their relevant sections in Applications, where they can be explained in greater detail; removing the description of positive/negative types, since these are already covered later in the article - and have their own pages anyway. -- Trevithj ( talk) 22:09, 29 March 2012 (UTC)
Any objections if I remove the Audio feedback and Performance appraisal sections in the lead? They aren't really in the right context here, and are already covered in the disambiguation page and the "See also" list. -- Trevithj ( talk) 00:43, 18 April 2012 (UTC)
Proposal is to return the "ideal feedback model" image to the electronics section, and put a more generic image in the lead. The existing image IMO better serves the article if placed in the Electronics section, for reasons stated here.
I agree with User:Teapeat that the lead image needs to summarize the overall topic in an abstract way. The image I propose follows Senge's definition of feedback as "any reciprocal flow of influence ... every influence is both cause and effect", or Astrom & Murray's "situation in which two (or more) dynamical systems are connected together..." and would consist of two abstract entities connected to each other by arrows representing a loop of influence or causality. This is equally applicable to either type of feedback, and applies broadly to any example.
Other options are welcome. -- Trevithj ( talk) 22:20, 19 April 2012 (UTC)
Okay, after a month and no comments, I will move the "ideal feedback model" diagram back down to the Electronics section, with cited reference to (and diagram description from) W.Chen. -- Trevithj ( talk) 23:13, 17 May 2012 (UTC)
Is email administration really a social science? Maybe in the 90's it was, but we must have passed that stage. — Preceding unsigned comment added by 14.200.55.92 ( talk) 08:08, 30 November 2013 (UTC)
The "Types of Feedback" section was poorly written, and jumped immediately to a rather unclear discussion on the social-science meaning of the words "positive feedback" and "negative feedback". I've tried to rewrite it to make it a bit clearer. Geoffrey.landis ( talk) 16:12, 27 June 2014 (UTC)
The current definition used in the article to scope it is:
The issue I have with this is that it doesn't map well onto many feedback loops. For example a ball-cock/float valve does not communicate information in any normal sense, it physically closes the valve. Another example is climate, there are feedback loops on the rainfall and temperature that go via bacteria seeding clouds. These are not information in any normal sense. Information is usually considered as a trigger to action, whereas these are mechanical feedback loops that physically force negative feedback.
Additionally there is the question of what the 'same' phenomenon means; it could mean practically anything.
I propose to change it to:
This is slightly more abstract, but the concept of the 'state of the system' is fully general, as is the term 'influence' and the notion of the loop being closed and causal. These seem to be wider than the current definition and the minimum necessary ingredients for feedback to be said to occur.
I welcome comments. GliderMaven ( talk) 16:10, 10 August 2014 (UTC)
Dicklyon has pointed to what is the point of WP: to report the contents of reliable sources and not WP editors' personal and unsourced views. If a definition is to be discussed, it should be related to sources. It doesn't have to copy them verbatim, of course, but it should be a clear presentation of the content of sources. Brews ohare ( talk) 18:37, 10 August 2014 (UTC)
Before becoming embroiled in extreme positions on what is or is not feedback, it is worthwhile to consider Ashby's discussion of the limitations of this concept.
In Ashby's extensive work, on p. 58, article 4/10 he compares the case of two parts of a system, P and R and contrasts the case where P affects R but not the contrary, denoted P → R, with the case where each affects the other, denoted P R. In this last case he says "when this circularity of action exists between the parts of a dynamic system, feedback may be said to be present." He continues:
Among these, he considers those
He goes on to say that for the mathematician the requirement of a physical connection renders the theory "chaotic and riddled with irrelevancies". Ashby continues:
The implications here are that feedback has a number of possible definitions, and whatever definition is chosen it will prove immaterial to the understanding of complex systems. This idea becomes paramount in philosophical considerations like enactivism, emergence, self-organization, and situated cognition.
With that in mind, a view of feedback in this article that takes a somewhat skeptical and distanced view of the matter seems appropriate, presenting a variety of views and their limitations. Brews ohare ( talk) 22:08, 10 August 2014 (UTC)
Ashby advocates the "circular causality" idea - which I believe is the thinking behind GliderMaven's suggestion. While historically the term "feedback" has referred to "output-to-input" (or out→in for short) the causal loop idea is more generic - which is what we want here.
I can see that the information term could be confusing. If we are using a specific term in a generic sense, we could either make that clearer, or simply drop the term. I would argue that the same can be said for the term "process", which strongly implies out→in.
Regards causal loops: it seems we have two basic models: a system that influences itself, or two parts of a system that influence each other. (S→S or P R) I suggest they are the same idea, with differing levels of detail. Which is the more convenient for purposes of explanation? Trevithj ( talk) 19:58, 11 August 2014 (UTC)
Sorry about my broken edit, and thanks for fixing it, GM. I must have been looking at an old version.
On the Ramaprasad ref and definition, I don't know what to think. Does someone have a copy I can read? As an attempt at a "general" definition it seems way narrow, so it's not clear why we are including it there. Dicklyon ( talk) 16:34, 26 September 2014 (UTC)
The paper discusses the lack of a commonly accepted definition of the concept of feedback in management theory, dealing with communications networks and decision processes in living systems at the organization level. It proposes a general definition. It deals with living systems at the organization level, including the total system and all subsystems. Implications of the proposed definition to current conceptualizations of feedback processes in management are explored.
KEY WORDS: organization, decision making, feedback, management theory.
Thus as long as the definition of the concept of feedback used by management theorists is at variance with the definitions used in cybernetics, general systems theory, control theory, etc., knowledge from these disciplines cannot be translated into the context of management. ... On the other hand, there is no universally accepted definition of feedback outside management theory either.
At present, the lede states:
This definition of negative feedback suggests that it is an event that occurs when the fed-back information acts. The idea that negative feedback refers to an 'event' seems awkward to me because it emphasizes a transient behavior, rather than the consequence of a particular arrangement or set-up. I am also disturbed by the notion of information as an agent that can 'act'.
Some sources refer to negative feedback as a process. 1 2 3 or as a form of control, 4, or as a particular circumstance. 5.
That suggests this change:
In negative feedback, a signal fed back into a system is reduced or canceled so that change is minimized
Of course, a different reference could be chosen. Brews ohare ( talk) 17:25, 27 September 2014 (UTC)
This edit removed extensive sections dealing with educational and other aspects of feedback without providing any feedback here on the Talk page. The in-line editorial comment was made regarding the educational material that article is not about individual uses of feedback, it is about feedback loops; the entire loop- and in quantitative science, and about the social science material removed the most egregious examples and unreferenced material.
No doubt, some changes were warranted. However, some discussion also is warranted. In particular, the idea that this article should be restricted to "quantitative science" is rather debatable, particularly because cybernetics arose in this context.
There appears to be a prejudice here that 'feedback' in other areas is used only in the everyday sense of rejection and unfavorable comment. However, that is not the case. Material where feedback is used to imply a detailed critique aimed at modifying a process or organization seems to me an appropriate topic for this article. While overlap will occur with the subjects of Reinforcement or "operant conditioning", and Reinforcement learning, the more technical aspects of feedback are mentioned in these fields and this article could usefully include some subsections that briefly make these connections. Brews ohare ( talk) 17:56, 27 September 2014 (UTC)
Reinforcement is an aspect of the use of feedback, but it is only part of it. And even if were everything, which it is not, this article should mention it as some readers will visit this page with applications to education and management in mind, and the connection with cybernetics, and wonder why it is not here. Brews ohare ( talk) 00:32, 30 September 2014 (UTC)
Brews, why the hangup on "feedback mechanism"? Isn't an X mechanism just a mechanism involving X? What needs to be said about that? And where did you get that crazy definition you had added? Dicklyon ( talk) 00:42, 30 September 2014 (UTC)
Feedback mechanism – the action or means used to act upon feedback information, to implement a response
Yes, feedback mechanism is common enough in sources. But what do you want to say about it that's worth a mention in the lead? So far I don't see anything. And I have no issue with sources, which is why I address you, Brews; tell us why you think this is worth a mention in the lead. Dicklyon ( talk) 04:13, 30 September 2014 (UTC)
The lead sentence reads:
Presumably this source is meant to support the 'chain of cause-and-effect' claim. However, this idea does not show up in this source. The word 'chain' and the words 'cause' and 'effect' do not appear in this source. An alternative source is:
This source states:
A bit disconcerting for the lede is that Ford restricts the 'chain of cause-and-effect' to a particular type of feedback, namely information feedback, and suggests that the 'chain of cause-and-effect' is not actually the feedback (which is the information, of course) but the mechanism that creates the feedback.
My suggestion is that the Ford source replace the present source that has nothing to do with the lead sentence, and that some thought be given as to what is the feedback and what is the feedback mechanism. 1 2 3 4 5 Brews ohare ( talk) 15:19, 30 September 2014 (UTC)
In this connection, CW Kirkwood suggests (§1.3 Feedback and causal loop diagrams in this source) that "Feedback is defined as the transmission and return of information (Richardson & Pugh, 1981)" This source is G. P. Richardson and A. L. Pugh III (1981). Introduction to System Dynamics Modeling with DYNAMO. Cambridge, Massachusetts: Productivity Press. Brews ohare ( talk) 16:06, 30 September 2014 (UTC)
This definition is in widespread use. Brews ohare ( talk) 16:09, 30 September 2014 (UTC)
This feedback definition is not the main point. The main point is replacing the source. The next point is distinguishing between feedback and the way feedback is arranged for, the feedback mechanism. Brews ohare ( talk) 21:53, 30 September 2014 (UTC)
The lede now reads:
This chapter describes causal loop diagrams to portray the information feedback at work in a system. The word causal refers to cause-and-effect relationships. The word loop refers to a closed chain of cause and effect that creates the feedback.
This version has replaced the previous version:
...the chain of the transmission and return of information: in what we shall from now on call the chain of feedback.
This chapter describes causal loop diagrams to portray the information feedback at work in a system. The word causal refers to cause-and-effect relationships. The word loop refers to a closed chain of cause and effect that creates the feedback.
This change was made by GliderMaven with the comment removed unnecessary definition that is probably wrong, or at least incomplete and deceptive, an action supported by Dicklyon with the comment It's not a particularly useful or clarifying definition. These are rather odd evaluations, as the definition originates with Norbert Wiener as cited above, a particularly authoritative source, and additionally is found in Morris' dictionary also cited above, in Ford, and has wide currency.
In addition, the earlier version and its three sources emphasize feedback as an exchange of information, but also that for it to work we need a mechanism to insure consequences. There exist a variety of structures for putting feedback to work, but the various possible mechanisms can be described generally as "closed chains of cause and effect". Although the present lede retains Ford as a source, his identification of these two aspects, the information exchange and its activation,(also pointed out by Wiener and Morris) has been lost. Brews ohare ( talk) 20:41, 1 October 2014 (UTC)
The version of the lede installed by GliderMaven with Dicklyon's blessing has the demerits of containing no definition of 'feedback' (it states, not what it is in fact, but only circumstances attending its appearance - it 'occurs when...' ), and of ignoring the role of information pointed out by a seminal source (Wiener) and adopted by many subsequent authors. The present lede employs a source focused upon information (Ford) without benefiting from its teachings. This version removed by GliderMaven has none of these defects and is more completely sourced. Brews ohare ( talk) 14:34, 2 October 2014 (UTC)
In making this change in the lede that de-emphasizes the importance of information, GliderMaven is reversing his previous recommendation for a generality of approach involving explicit reference to the conduit of information. Why? Brews ohare ( talk) 16:16, 4 October 2014 (UTC)
The section on Feedback#Oscillator and on Feedback#Flip-flop make no connection to the role of feedback in their operation. The oscillator subsection is little more than a repeat of the lede for Electronic oscillator, and likewise, the subsection on flip-flops is little more than a repetition of the lede for Flip-flop (electronics). Without clearly describing the nature of the feedback used in these applications and its role, preferably sourced and not just some WP editor's opinion, these subsections have no place in an article on feedback. In their present form, these subsections could be replaced by See also links at the end of the feedback article. Brews ohare ( talk) 18:11, 11 November 2014 (UTC)
A possibly useful discussion for oscillators is provided by Kal "Sinusoidal oscillations can be produced using two different types of principle: negative resistance oscillators and feedback oscillators." and by Chattopadhyay "Both negative-resistance and feedback oscillators can be sinusoidal and relaxation types." Brews ohare ( talk) 18:56, 11 November 2014 (UTC)
This article is poorly written and it's not concise. The introduction is lousy and it does not list positive feedback so I wonder why only negative feedback should be listed. The section on terminology implies two confusing definitions and later, in the electronic engineering section, a third definition based on direction is included. Later, in the negative feedback loops section, a definition based on phase is introduced. In my opinion, the definition in terms of direction and phase are confusing or even incorrect. Also, if multivibrators are a form of positive feedback, they should be listed under the positive feedback section. Oscillators are presented and my understanding is that they use positive feedback. This is not explained or mentioned at all. Lastly, as far as I know, latches use positive feedback. This is not state anywhere in the article. Nothing is mentioned about flip-flops either. Both oscillators and latches/flip-flops should be listed under their respective categories. This article needs a huge rework.
ICE77 ( talk) 16:50, 14 June 2015 (UTC)
> A negative feedback loop is one that tends to slow down a process, whereas the positive feedback loop tends to accelerate it.
This sentence is capable of being completely misunderstood, seemingly supporting a common misunderstanding in certain fields of biology, namely that systems possessing a positive feedback tend to respond faster, and systems possessing a negative feedback tend to respond slower.
The problem arises because it is not stated at all as compared to what exactly a "negative feedback [..] tends to slow down a process". That is: given a process with a positive or negative feedback loop, how does the corresponding process without the feedback loop exactly looks like? This is very problematic because in a very common way to answer this question, rather the direct opposite of the statement above holds.
Example: Consider the linear system
where 0<k<1 corresponds to a positive feedback of "strength" k, k<0 to a negative feedback of "strength" -k, and k=0 to "no feedback". Consider the input u(t) switching from zero to one at t=0. The solution is , and the time constant is . That is, a positive feedback (k>0) increases the time constant (makes the system slower), and a negative feedback (k<0) decreases the time constant (makes it faster).
I propose to completely delete the statement rather than keeping it in its current form. — Preceding unsigned comment added by Langmo ( talk • contribs) 12:50, 22 February 2017 (UTC)
this article/ subject matter & its related concepts- are they more closely associated with life sciences or with engineered systems? can anyone estimate a proportion break-down, like a percentage that it pertains to each?
leaving this question unanswered will leave the article muddled and possibly confusing, depending on the initial assumptions of the reader. skak E L 19:41, 9 July 2020 (UTC)
Op-amp with nagative positive feedback 2402:3A80:16E1:87D:0:3B:122A:2A01 ( talk) 08:57, 22 February 2022 (UTC)
MANAGING 196.189.127.101 ( talk) 03:32, 21 March 2024 (UTC)
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is external linking allowed?, in any case much good info in http://prof.usb.ve/williamc/Mejoramiento/historia.html should be made available here
in electronics the para are disordered, positive feedback (suject of great Armstrong deForset patent dispute)predates Black's negative feedback amplifier and should be refered to first, PID is a subset of negative feedback control techniques :jcox
--- I don't believe that the explanation of audio feedback is correct. It identifies the frequency of feedback noise as related to the transit time through the system (Implying it's a matter of repeating the waveform, the effect you might get with digital echo or flange). But I'm 95% sure that's completely irrelevant in a system like this, the waveform is completely obliterated by all the transitions made, all you're left with is frequencies that approximate those you started with.
OK, a quick test: I was able to get audible feedback with a 1/2 second delay in the loop, which should give a frequency of 2 hz, 5 octaves below audible.
So I'm rather sure the frequency of feedback is not determined by transit time, but by the frequency response of the whole system. All real world systems contain some capacitance and inductance, meaning they all act as very wide, low, bandpass filters. But when you amplify and feedback the filtered sound into the filtered sound, you've naturally created an oscillator (the simplest forms of analog oscillators work on exactly this principle).
So unless anyone objects I'm going to change the explanation to reflect this. User:Wji
Although feedback was perhaps discovered during the course of the development of electronics, it exists in many natural processes and the word (although not present in earlier dictionaries, for example the original OED) represents a concept in general use outside engineering. Therefore the article should begin with the general concept but include a substantial section on control theory. I was first introduced to feedback during training on servo mechanisms many years ago and am a bit rusty, but I clearly remember it took both positive and negative feedback to make them work. What we call feedback like with a microphone is perhaps not feedback in the sense we are using it here. User:Fredbauder
I agree that there is more than one sense of the word feedback. The Penguin Dictionary of Electronics, for example, has separate entries for feedback in the general sense and feedback control loop in the specific context of control systems. The Chambers Science and Technology Dictionary has headings for feedback (acoustic), feedback (telecommunications) and feedback control loop, so perhaps there are really three different concepts. If we wish to separate the general from the particular, I would suggest the following structure for the Wikipedia (with separate articles for hunting and feedback):
Do you think this is reasonable? Unfortunately it contradicts your idea of putting the natural phenomena first. My scheme lists things in the order of discovery by man, whereas yours is nature-based. I cannot say which is better.
As for the microphone example, this is an illustration of feedback in the electronic (or electroacoustic) sense, not in the control loop sense. The feedback is always positive, because sound from the loudspeakers is always added to, never subtracted from, the sound entering the microphone. What changes is the loop gain, which varies as the user moves the microphone relative to the speakers. As soon as the loop gain exceeds unity, the system howls. This effect is independent of frequency. I believe that a system with negative feedback can only become unstable if the signal frequency exceeds the bandwidth of the feedback loop.
In control theory you can have multiple feedback paths (often three: proportional, integral and derivative) and it is meaningless to talk about overall positive or negative feedback, because the three paths may have different characteristics. -- Heron
What I suggest is a simple introduction which includes the general case, followed by as much specialized technical information as you feel appropriate. I agree the notion of postive and negative is applicable only to 2 dimensional systems, but I think it should remain in the introduction. I don't think organization around order of discovery is good; I prefer organization to start with a brief general introduction using simple language and concepts followed by (in this case) an engineering section, followed by the ways the concept has been adapted to natural systems. I guess runaway positive feedback is what we are talking about with apmplifiers. Fred Bauder
I divided the article into sections, without changing the words much. I may go further and remove the acoustic example to a separate article, but I'll leave 'hunting' where it is. -- Heron
I have been bold and removed the acoustic feedback section totally. I have linked the existing article at Audio feedback to the disambiguation page. The main differences in the removed section (reproduced below) lacking in the original page are the points about the band-pass filter and the electronic oscillator.
I believe the band-pass filter point is incorrect anyway. True, all systems have some kind low and high pass filter in them, but this is generally well outside the human range of hearing, and in any case, makes no difference to the presence of feedback. The deleted section was also vague as to whether this was affecting the presence or nature of the feedback, but if it were just the latter, there are plenty of other factors involved (at the very least, the inherant EQ of the system would be much more important).
Also, the electronic oscillator point seems slightly amibiguous too, although I could understand if people wanted this link in the main article. It might be worth pointing out that the simplicity is certainly not in the waveform, but in the construction. -- postglock 07:49, 6 Jun 2005 (UTC)
Main article: Audio feedback.
A well-known example of runaway positive feedback in electronic systems is called "howl" or "howl-round". This occurs in public address systems when sound from the loudspeakers reaches the microphone, is amplified by the system, and is then fed back into the system at even higher volume. All electrical systems contain capacitance and inductance and so act as band-pass filters responding better to certain frequencies. In a single loop through the system, this effect is negligible, but it becomes severe when the signal passes through the system repeatedly. This effect is the basis of the simplest kinds of analogue electronic oscillator.
postglock- lemme know if my last version works for you. thankz, Ished-out amounts of Vonn-ness 14:19, 10 September 2005 (UTC)
> Feedback is the signal that is looped back to control a system within itself.
The mention of "signal" and "control" seem overly teleological. Here are some definitions of feedback loop from around the net; a definition of feedback ought to work well with these sorts of definitions:
What is your favorite, least constraining definition of feedback?
love, raiph 05:11, 10 October 2006 (UTC)
There's a long laundry list of important theories, phenomena and more built directly on top of feedback loops that aren't mentioned on this page but should, imo, be considered. (I think I could easily list a dozen, and maybe a hundred, but the specifics aren't my point and I really don't want to get into that game yet if we can avoid it.)
Conversely, much of what's on the page right now seems too detailed, even for me, someone who's been intellectually focused on feedback loops for over a decade.
I propose I/we refactor the page. The introduction should be as general as possible. A History section seems a natural. Maybe an Examples section. I see most of the details of particular feedback phenomena going on their own pages.
Comments?
love, raiph 03:44, 3 October 2006 (UTC)
I am used to finding concise explanations in the first paragraphs of a Wikipedia article, and would propose the following thumbnail sketch of "feedback" for the first para. I haven't edited an article so won't presume, but this example is technically accurate and memorable:
Feedback: an action changes a system and then the system changes the action.
Positive feedback increases the action: you step on the brake pedal in a moving car, and the car slows, pushing your foot down harder on the brake.
Negative feedback decreases the action: you step on the gas pedal and the car accelerates, pulling your foot off the gas pedal.
If this is appropriate perhaps someone will include it.
68.98.117.241 23:25, 27 January 2007 (UTC)
I agree with the above change, and suggest that the current definitions in Types of Feedback are in fact incorrect and misleading. An example of negative feedback is a thermostat heating a room that is too cold. This is not reducing output, but increasing output (from the heater) or increasing input (into the room).
I also feel that the "bipolar feedback" definition is confusing - both positive and negative feedback mechanisms can cause output to change in either direction, so both are bipolar. But feedback can't be positive and negative at the same time.
Finally, hunting is more correctly a case of over-control, where a negative feedback signal overshoots the mark. This is a type of oscillation, but doesn't strictly involve positive feedback at all.
I suggest that this article could benefit from better clarity of the terms positive and negative earlier on. I had started to edit, but realized that my background (electronics) is probably too narrow for a general article.
Trevithj (
talk) 20:56, 18 August 2008 (UTC)
There is a Rush album called Feedback that should be included in the disambiguation page. -- The Fwanksta
A splitting of the article has been proposed on 15 March 2007. Nobody made any suggestions about this untill I yesterday removed the splitting tag. Now today User:Intgr reversed this with the argument:
Now I think there are at least four good reasons not to split:
I think this article is only in need of an expert, who creates a more general introduction, which shows how all these aspects are related to one central concept. For example this article is comparable with the complexity article. This is also one paradigm, with different applications in the disciplines. - Mdd 18:53, 28 August 2007 (UTC)
Their is no need to spread so related knowledge over a number of small articles - Mdd 05:49, 29 August 2007 (UTC)
Their are more arguments agains spliting the article:
I also think that:
Now I think I look at the concept of feed back from a kind of fundamental "systems science point of view". In this perspective the control theory aspect is not whole separate aspects beside e.g. biological, economical, electronical, ergonomic and mechanical forms of feed back. The control theory aspects with their mathematical forms of representation are the fundamentals for all kind of specialized applications.
I do agree something has to be done with this article. In it's current form it's just a collection of seemingly unrelated facts. I'll see if I can improve this a little. - Mdd 20:14, 7 September 2007 (UTC)
I removed the tag to split the article because there was no response the last four weeks. - Mdd 19:59, 12 November 2007 (UTC)
Hello. This article has two references, which is good. I added a "citations missing" tag because most sections have no inline citations and thus there is no way for the reader to know to which of the two refs any particular piece of information is sourced. OK in advance from my point of view to remove or move or change this tag. Best wishes. - Susanlesch 18:43, 12 November 2007 (UTC)
The example of vacuum advance control in older automotive ignition systems is bogus. Such systems did not employ any kind of feedback mechanism; i.e., they did not sense or react to any change they produced. —Preceding unsigned comment added by 24.22.7.221 ( talk) 21:31, 17 January 2008 (UTC)
The overview starts with the following sentence:
both is followed by three items instead of two. Hence, both should be removed. [ Georg] —Preceding unsigned comment added by 206.113.192.12 ( talk) 17:04, 25 January 2008 (UTC)
This seems confusing. How can feedback be both positive and negative at the same time? These are exclusive, surely. If this means a switching function, where the feedback changes between positive and negative, then the definition should clarify this. If it means a balancing, then two feedback loops must be involved (one positive, one negative.)
I have searched several online sources, and they all seem to cite each other (including this one) but I can't find an original definition. I have noted several references to "bipolar feedback transistors", but suspect that means a feedback loop involving a bipolar transistor, rather than "bipolar feedback" involving a transistor.
If bipolar feedback is present in many systems, can someone provide an example?
Trevithj (
talk) 02:43, 10 September 2008 (UTC)
I suggest that the primary purpose of the "Types of feedback" section is to distinguish negative feedback from positive feedback and outline other commonly used terms for types of feedback. This section should not get bogged down into fine details. The material that discusses the history of negative feedback should be moved into the Negative Feedback article. 203.206.220.108 ( talk) 00:44, 8 November 2008 (UTC)
The subsection "In electronic engineering" re-explains the concepts of negative feedback and positive feedback, which are not particularly specific to electronic engineering. Anyway, the section that contains this subsection is "Applications" so this is not the right place for explaining a general principle. 203.206.220.108 ( talk) 01:28, 8 November 2008 (UTC)
- 3 - the feedback signal does not change when the input signal changes, in which case there is no feedback. This is known as a Linear system.
If no feedback is an example of feedback then sitting on your bum is an example of flying. In addition linear systems can have feedback, and non-linear systems do not require feedback. Thus the above should be deleted. 203.206.220.108 ( talk) 12:31, 28 December 2009 (UTC)
This article has the same naming problem that correlation article had years ago. People at first mislabeled correlation as positive and negative. That is nebulous. It was correctly changed to direct and inverse correlation.
This article suffers from the same issue. It should NOT be positive and negative feedback. Instead the proper more accurate terms are converging and expanding feedback. The article needs renamed as well.
173.188.7.24 ( talk) 21:19, 4 March 2012 (UTC)
If no objection I would like to insert the below cited definition into the preamble, just above "feedback is also a synonym for...":
I hesitate only because the definition comes from the Behavioral Sciences, and may not be broadly applicable. Although it looks pretty good to me. -- Trevithj ( talk) 22:04, 15 March 2012 (UTC)
Above changes made, and also modified the synonym "feedback signal", since this definition makes that (old) distinction unnecessary/redundant. -- Trevithj ( talk) 05:51, 29 March 2012 (UTC)
As a suggestion, I would like to add a lead to the Types of Feedback section ... something like this:
-- Trevithj ( talk) 20:48, 22 March 2012 (UTC)
I see a need to make this section:
I propose: describing the history of the term "feed-back", and show its adoption from verb phrase to noun; moving the examples to their relevant sections in Applications, where they can be explained in greater detail; removing the description of positive/negative types, since these are already covered later in the article - and have their own pages anyway. -- Trevithj ( talk) 22:09, 29 March 2012 (UTC)
Any objections if I remove the Audio feedback and Performance appraisal sections in the lead? They aren't really in the right context here, and are already covered in the disambiguation page and the "See also" list. -- Trevithj ( talk) 00:43, 18 April 2012 (UTC)
Proposal is to return the "ideal feedback model" image to the electronics section, and put a more generic image in the lead. The existing image IMO better serves the article if placed in the Electronics section, for reasons stated here.
I agree with User:Teapeat that the lead image needs to summarize the overall topic in an abstract way. The image I propose follows Senge's definition of feedback as "any reciprocal flow of influence ... every influence is both cause and effect", or Astrom & Murray's "situation in which two (or more) dynamical systems are connected together..." and would consist of two abstract entities connected to each other by arrows representing a loop of influence or causality. This is equally applicable to either type of feedback, and applies broadly to any example.
Other options are welcome. -- Trevithj ( talk) 22:20, 19 April 2012 (UTC)
Okay, after a month and no comments, I will move the "ideal feedback model" diagram back down to the Electronics section, with cited reference to (and diagram description from) W.Chen. -- Trevithj ( talk) 23:13, 17 May 2012 (UTC)
Is email administration really a social science? Maybe in the 90's it was, but we must have passed that stage. — Preceding unsigned comment added by 14.200.55.92 ( talk) 08:08, 30 November 2013 (UTC)
The "Types of Feedback" section was poorly written, and jumped immediately to a rather unclear discussion on the social-science meaning of the words "positive feedback" and "negative feedback". I've tried to rewrite it to make it a bit clearer. Geoffrey.landis ( talk) 16:12, 27 June 2014 (UTC)
The current definition used in the article to scope it is:
The issue I have with this is that it doesn't map well onto many feedback loops. For example a ball-cock/float valve does not communicate information in any normal sense, it physically closes the valve. Another example is climate, there are feedback loops on the rainfall and temperature that go via bacteria seeding clouds. These are not information in any normal sense. Information is usually considered as a trigger to action, whereas these are mechanical feedback loops that physically force negative feedback.
Additionally there is the question of what the 'same' phenomenon means; it could mean practically anything.
I propose to change it to:
This is slightly more abstract, but the concept of the 'state of the system' is fully general, as is the term 'influence' and the notion of the loop being closed and causal. These seem to be wider than the current definition and the minimum necessary ingredients for feedback to be said to occur.
I welcome comments. GliderMaven ( talk) 16:10, 10 August 2014 (UTC)
Dicklyon has pointed to what is the point of WP: to report the contents of reliable sources and not WP editors' personal and unsourced views. If a definition is to be discussed, it should be related to sources. It doesn't have to copy them verbatim, of course, but it should be a clear presentation of the content of sources. Brews ohare ( talk) 18:37, 10 August 2014 (UTC)
Before becoming embroiled in extreme positions on what is or is not feedback, it is worthwhile to consider Ashby's discussion of the limitations of this concept.
In Ashby's extensive work, on p. 58, article 4/10 he compares the case of two parts of a system, P and R and contrasts the case where P affects R but not the contrary, denoted P → R, with the case where each affects the other, denoted P R. In this last case he says "when this circularity of action exists between the parts of a dynamic system, feedback may be said to be present." He continues:
Among these, he considers those
He goes on to say that for the mathematician the requirement of a physical connection renders the theory "chaotic and riddled with irrelevancies". Ashby continues:
The implications here are that feedback has a number of possible definitions, and whatever definition is chosen it will prove immaterial to the understanding of complex systems. This idea becomes paramount in philosophical considerations like enactivism, emergence, self-organization, and situated cognition.
With that in mind, a view of feedback in this article that takes a somewhat skeptical and distanced view of the matter seems appropriate, presenting a variety of views and their limitations. Brews ohare ( talk) 22:08, 10 August 2014 (UTC)
Ashby advocates the "circular causality" idea - which I believe is the thinking behind GliderMaven's suggestion. While historically the term "feedback" has referred to "output-to-input" (or out→in for short) the causal loop idea is more generic - which is what we want here.
I can see that the information term could be confusing. If we are using a specific term in a generic sense, we could either make that clearer, or simply drop the term. I would argue that the same can be said for the term "process", which strongly implies out→in.
Regards causal loops: it seems we have two basic models: a system that influences itself, or two parts of a system that influence each other. (S→S or P R) I suggest they are the same idea, with differing levels of detail. Which is the more convenient for purposes of explanation? Trevithj ( talk) 19:58, 11 August 2014 (UTC)
Sorry about my broken edit, and thanks for fixing it, GM. I must have been looking at an old version.
On the Ramaprasad ref and definition, I don't know what to think. Does someone have a copy I can read? As an attempt at a "general" definition it seems way narrow, so it's not clear why we are including it there. Dicklyon ( talk) 16:34, 26 September 2014 (UTC)
The paper discusses the lack of a commonly accepted definition of the concept of feedback in management theory, dealing with communications networks and decision processes in living systems at the organization level. It proposes a general definition. It deals with living systems at the organization level, including the total system and all subsystems. Implications of the proposed definition to current conceptualizations of feedback processes in management are explored.
KEY WORDS: organization, decision making, feedback, management theory.
Thus as long as the definition of the concept of feedback used by management theorists is at variance with the definitions used in cybernetics, general systems theory, control theory, etc., knowledge from these disciplines cannot be translated into the context of management. ... On the other hand, there is no universally accepted definition of feedback outside management theory either.
At present, the lede states:
This definition of negative feedback suggests that it is an event that occurs when the fed-back information acts. The idea that negative feedback refers to an 'event' seems awkward to me because it emphasizes a transient behavior, rather than the consequence of a particular arrangement or set-up. I am also disturbed by the notion of information as an agent that can 'act'.
Some sources refer to negative feedback as a process. 1 2 3 or as a form of control, 4, or as a particular circumstance. 5.
That suggests this change:
In negative feedback, a signal fed back into a system is reduced or canceled so that change is minimized
Of course, a different reference could be chosen. Brews ohare ( talk) 17:25, 27 September 2014 (UTC)
This edit removed extensive sections dealing with educational and other aspects of feedback without providing any feedback here on the Talk page. The in-line editorial comment was made regarding the educational material that article is not about individual uses of feedback, it is about feedback loops; the entire loop- and in quantitative science, and about the social science material removed the most egregious examples and unreferenced material.
No doubt, some changes were warranted. However, some discussion also is warranted. In particular, the idea that this article should be restricted to "quantitative science" is rather debatable, particularly because cybernetics arose in this context.
There appears to be a prejudice here that 'feedback' in other areas is used only in the everyday sense of rejection and unfavorable comment. However, that is not the case. Material where feedback is used to imply a detailed critique aimed at modifying a process or organization seems to me an appropriate topic for this article. While overlap will occur with the subjects of Reinforcement or "operant conditioning", and Reinforcement learning, the more technical aspects of feedback are mentioned in these fields and this article could usefully include some subsections that briefly make these connections. Brews ohare ( talk) 17:56, 27 September 2014 (UTC)
Reinforcement is an aspect of the use of feedback, but it is only part of it. And even if were everything, which it is not, this article should mention it as some readers will visit this page with applications to education and management in mind, and the connection with cybernetics, and wonder why it is not here. Brews ohare ( talk) 00:32, 30 September 2014 (UTC)
Brews, why the hangup on "feedback mechanism"? Isn't an X mechanism just a mechanism involving X? What needs to be said about that? And where did you get that crazy definition you had added? Dicklyon ( talk) 00:42, 30 September 2014 (UTC)
Feedback mechanism – the action or means used to act upon feedback information, to implement a response
Yes, feedback mechanism is common enough in sources. But what do you want to say about it that's worth a mention in the lead? So far I don't see anything. And I have no issue with sources, which is why I address you, Brews; tell us why you think this is worth a mention in the lead. Dicklyon ( talk) 04:13, 30 September 2014 (UTC)
The lead sentence reads:
Presumably this source is meant to support the 'chain of cause-and-effect' claim. However, this idea does not show up in this source. The word 'chain' and the words 'cause' and 'effect' do not appear in this source. An alternative source is:
This source states:
A bit disconcerting for the lede is that Ford restricts the 'chain of cause-and-effect' to a particular type of feedback, namely information feedback, and suggests that the 'chain of cause-and-effect' is not actually the feedback (which is the information, of course) but the mechanism that creates the feedback.
My suggestion is that the Ford source replace the present source that has nothing to do with the lead sentence, and that some thought be given as to what is the feedback and what is the feedback mechanism. 1 2 3 4 5 Brews ohare ( talk) 15:19, 30 September 2014 (UTC)
In this connection, CW Kirkwood suggests (§1.3 Feedback and causal loop diagrams in this source) that "Feedback is defined as the transmission and return of information (Richardson & Pugh, 1981)" This source is G. P. Richardson and A. L. Pugh III (1981). Introduction to System Dynamics Modeling with DYNAMO. Cambridge, Massachusetts: Productivity Press. Brews ohare ( talk) 16:06, 30 September 2014 (UTC)
This definition is in widespread use. Brews ohare ( talk) 16:09, 30 September 2014 (UTC)
This feedback definition is not the main point. The main point is replacing the source. The next point is distinguishing between feedback and the way feedback is arranged for, the feedback mechanism. Brews ohare ( talk) 21:53, 30 September 2014 (UTC)
The lede now reads:
This chapter describes causal loop diagrams to portray the information feedback at work in a system. The word causal refers to cause-and-effect relationships. The word loop refers to a closed chain of cause and effect that creates the feedback.
This version has replaced the previous version:
...the chain of the transmission and return of information: in what we shall from now on call the chain of feedback.
This chapter describes causal loop diagrams to portray the information feedback at work in a system. The word causal refers to cause-and-effect relationships. The word loop refers to a closed chain of cause and effect that creates the feedback.
This change was made by GliderMaven with the comment removed unnecessary definition that is probably wrong, or at least incomplete and deceptive, an action supported by Dicklyon with the comment It's not a particularly useful or clarifying definition. These are rather odd evaluations, as the definition originates with Norbert Wiener as cited above, a particularly authoritative source, and additionally is found in Morris' dictionary also cited above, in Ford, and has wide currency.
In addition, the earlier version and its three sources emphasize feedback as an exchange of information, but also that for it to work we need a mechanism to insure consequences. There exist a variety of structures for putting feedback to work, but the various possible mechanisms can be described generally as "closed chains of cause and effect". Although the present lede retains Ford as a source, his identification of these two aspects, the information exchange and its activation,(also pointed out by Wiener and Morris) has been lost. Brews ohare ( talk) 20:41, 1 October 2014 (UTC)
The version of the lede installed by GliderMaven with Dicklyon's blessing has the demerits of containing no definition of 'feedback' (it states, not what it is in fact, but only circumstances attending its appearance - it 'occurs when...' ), and of ignoring the role of information pointed out by a seminal source (Wiener) and adopted by many subsequent authors. The present lede employs a source focused upon information (Ford) without benefiting from its teachings. This version removed by GliderMaven has none of these defects and is more completely sourced. Brews ohare ( talk) 14:34, 2 October 2014 (UTC)
In making this change in the lede that de-emphasizes the importance of information, GliderMaven is reversing his previous recommendation for a generality of approach involving explicit reference to the conduit of information. Why? Brews ohare ( talk) 16:16, 4 October 2014 (UTC)
The section on Feedback#Oscillator and on Feedback#Flip-flop make no connection to the role of feedback in their operation. The oscillator subsection is little more than a repeat of the lede for Electronic oscillator, and likewise, the subsection on flip-flops is little more than a repetition of the lede for Flip-flop (electronics). Without clearly describing the nature of the feedback used in these applications and its role, preferably sourced and not just some WP editor's opinion, these subsections have no place in an article on feedback. In their present form, these subsections could be replaced by See also links at the end of the feedback article. Brews ohare ( talk) 18:11, 11 November 2014 (UTC)
A possibly useful discussion for oscillators is provided by Kal "Sinusoidal oscillations can be produced using two different types of principle: negative resistance oscillators and feedback oscillators." and by Chattopadhyay "Both negative-resistance and feedback oscillators can be sinusoidal and relaxation types." Brews ohare ( talk) 18:56, 11 November 2014 (UTC)
This article is poorly written and it's not concise. The introduction is lousy and it does not list positive feedback so I wonder why only negative feedback should be listed. The section on terminology implies two confusing definitions and later, in the electronic engineering section, a third definition based on direction is included. Later, in the negative feedback loops section, a definition based on phase is introduced. In my opinion, the definition in terms of direction and phase are confusing or even incorrect. Also, if multivibrators are a form of positive feedback, they should be listed under the positive feedback section. Oscillators are presented and my understanding is that they use positive feedback. This is not explained or mentioned at all. Lastly, as far as I know, latches use positive feedback. This is not state anywhere in the article. Nothing is mentioned about flip-flops either. Both oscillators and latches/flip-flops should be listed under their respective categories. This article needs a huge rework.
ICE77 ( talk) 16:50, 14 June 2015 (UTC)
> A negative feedback loop is one that tends to slow down a process, whereas the positive feedback loop tends to accelerate it.
This sentence is capable of being completely misunderstood, seemingly supporting a common misunderstanding in certain fields of biology, namely that systems possessing a positive feedback tend to respond faster, and systems possessing a negative feedback tend to respond slower.
The problem arises because it is not stated at all as compared to what exactly a "negative feedback [..] tends to slow down a process". That is: given a process with a positive or negative feedback loop, how does the corresponding process without the feedback loop exactly looks like? This is very problematic because in a very common way to answer this question, rather the direct opposite of the statement above holds.
Example: Consider the linear system
where 0<k<1 corresponds to a positive feedback of "strength" k, k<0 to a negative feedback of "strength" -k, and k=0 to "no feedback". Consider the input u(t) switching from zero to one at t=0. The solution is , and the time constant is . That is, a positive feedback (k>0) increases the time constant (makes the system slower), and a negative feedback (k<0) decreases the time constant (makes it faster).
I propose to completely delete the statement rather than keeping it in its current form. — Preceding unsigned comment added by Langmo ( talk • contribs) 12:50, 22 February 2017 (UTC)
this article/ subject matter & its related concepts- are they more closely associated with life sciences or with engineered systems? can anyone estimate a proportion break-down, like a percentage that it pertains to each?
leaving this question unanswered will leave the article muddled and possibly confusing, depending on the initial assumptions of the reader. skak E L 19:41, 9 July 2020 (UTC)
Op-amp with nagative positive feedback 2402:3A80:16E1:87D:0:3B:122A:2A01 ( talk) 08:57, 22 February 2022 (UTC)
MANAGING 196.189.127.101 ( talk) 03:32, 21 March 2024 (UTC)