What is Feedback: Definition and 245 Discussions

Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to feed back into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems:

Simple causal reasoning about a feedback system is difficult because the first system influences the second and second system influences the first, leading to a circular argument. This makes reasoning based upon cause and effect tricky, and it is necessary to analyze the system as a whole.

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  1. B

    Negative and postive feedback.

    Well, this post was just calling me out. So my past few posts about transistors, and very good people that replied them, told me that I should embrace this new concept of feedback. We just learned it last week, and I wasn't so excited about it.(meh, just another technique to make transistors...
  2. G

    Magnetic motor idea for feedback

    a magnet rotating a generator attracted to an iron bar, on reaching the iron bar triggers a switch which turns the iron bar to an electromagnet set to repel the magnet which inturn is attracted to the next iron bar and so on. Yes the electromagnet is charged by a battery but if the rotation is...
  3. L

    How did I capture these intriguing feedback loop photos?

    Feedback loops can be very cheap and can be modified easily by things to produce some interesting photos. I used the attached setup to capture these images over 12 years ago and they are accurate to what you actually see on the screen within the maxed out limits of the hardware/software...
  4. B

    Need feedback if this is possible (first order removal based model)

    Please pardon my lack of understanding here. I am a scientist with just limited experience in calculus and de (long time ago too), but I am willing to learn. I'm in the process of working through a theoretical model for a wastewater treatment plant that removes constituents assuming first...
  5. L

    What is the role of RC in opamp feedback loop for Type 2 opamp compensators?

    I am trying to understand Type1, 2 and 3 opamp compensators used in DCDC converters. Type 1 is just an opamp integrator. Type 2 has a C in feedback loop with parallel RC. How does this boost the phase Margin? (page 307 - http://tinyurl.com/3qyt5dc) I understand phase and gain margin when...
  6. R

    Control and Feedback in electronic circuits

    I'm trying to understand the concept of a control system in electronics. In a control system, we have a substractor, forward path and feedback path. The forward path is described by a function g ( a gain function ) and the feedback by another function ( gain again ). The input is Xi and the...
  7. D

    Mathematical modeling of a feedback control system

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  8. A

    Analyzing the Movement of a Bicycle (requesting feedback)

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  9. B

    Self-Studying: Feedback Strategies for Students

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  10. R

    Feedback on a sound controlled light circuit

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  11. L

    Understanding Opamp Circuits with BJT Feedback

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  12. Y

    Difference Between Normal Feedback Controller and Robust Controller

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  13. M

    Electronic oscillator and negative feedback

    http://img707.imageshack.us/i/electronicsoscillator.jpg/ Dont know where to start for showing voltage difference at input is zero, suspose its something to do with non idealities of the op amp? For the oscillator question , kinda know how its works; there's positive saturation giving...
  14. E

    Velocity feedback damping in aircraft

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  15. S

    Resume website would love some feedback

    "Resume" website... would love some feedback! Hello to all, It's coming to be about that time when I'm going to start applying for both jobs and graduate school. Instead of just having a standard resume for jobs, I was thinking of perhaps having something a little bit more interactive and...
  16. S

    Grandfather Paradox vs. Feedback

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  17. K

    How does the ideal op-amp model explain the need for feedback?

    In an inverting opamp let the output be feedback to inverting input through a feedback resistor Rf. We write the direction of flow of current from input terminal to output terminal in the feedback resistor Rf. But if this direction is correct then how can we say that input is fed back?? it seems...
  18. J

    Control Systems: Uncertainties w/ State feedback & Observer controller

    Homework Statement Consider the continuous time state space model governed by: A = [-1 0;1 0] B = [1; 0] C = [1 -1] D = 0 a) suppose we are using the following state feedback and observer gains K = [k1 k2] L = [l1;l2] find the loop gain symbolically using MATLAB (aka find...
  19. A

    Feedback in Electronics: Definition & Meaning

    what is the meaning of feed back in electronics? thanks.
  20. Y

    Leó Szilárd invented a feedback protocol1

    http://www.nature.com/nphys/journal/vaop/ncurrent/full/nphys1821.html
  21. I

    Can I Provide Feedback on Book Proofreading Errors for Future Printings?

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  22. C

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    Dear SA/Ms: I am seeking feedback from active and inactive SA/Ms regarding both the current and possible future utility (if any) of BRS. I have two multiple choice questions; due to limitations of VB software I must apparently create two different polls to ask them. This poll contains...
  23. J

    Proving \lim_{x \to a} f(x) = \lim_{h \to 0} f(a+h): Analysis & Feedback

    So, I'm trying to prove that \lim_{x \to a} f(x) = \lim_{h \to 0} f(a+h) and I'm wondering if this "proof" is correct: Suppose that \lim_{x \to a} f(x) = l and \lim_{h \to 0} f(a+h) = m with l \neq m. Then, for any \varepsilon > 0 there must be some \delta > 0 such that 0 < |x-a| < \delta...
  24. G

    Strong negative feedback in Climate

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  25. S

    Explaining Quasar Feedback: A Guide for the Struggling

    can anyone explain quasar feedback.. having some trouble.
  26. D

    Oscillation conditions: Feedback phase shift

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  27. F

    Determine Posititive Feedback Gain in an Oscillator

    NOTE- Images are thumbnails, click to enlarge Homework Statement Show that the positive feedback gain expression for the circuit below is v2/v0 = 1/[3 + j(wL/R - R/WL)] (anything in red I added to the original problem) Homework Equations (above)The Attempt at a Solution Along with the below...
  28. D

    Feedback topology (MOSFET Clapp oscillator)

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  29. N

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  30. A

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  31. B

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  32. T

    What is the relationship between feedback and topology in control systems?

    Hi All, In my control systems lectures my professor talks about feedback changing the 'topology' of the system. Is he just talking about the structure of the block diagram changing, or is there some link to the topology which mathematicians refer to Regards, Thrillhouse86
  33. Andre

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  34. S

    Time of Motion with Negative Feedback

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  35. S

    What is feedback? what is the advantage of it?

    What is feedback? what is the advantages of it?
  36. M

    Want to Help with My PhD Qualifying Exam?

    Hi my name is Matt. I'm preparing to take my PhD qualifying exam which consists of a 25 minute PowerPoint presentation with oral questioning to follow. If anyone has a few minutes and would like to take a look and offer comments or questions it can be viewed at...
  37. I

    Negative Feedback Example: Gain & Feedback Factor

    While introducing negative feedback, my book gave the following example: Let the signal voltage be 101mV and the output voltage of the amplifier be 10V Out of this 10V a fraction (0.01) i.e. 100mV was made to feedback to the input circuit. The feedback circuit did not introduce any phase...
  38. mg0stisha

    Mathematica Feedback on Mathematica 7 and "Six Ideas That Shape Physics"

    Hello, I was just wondering if anyone has used the software Mathematica 7. I heard it's a really good program and with the new functions it looks great, i was just wanted to get some good user feedback from people who definitely know what they're talking about. Thanks! P.S. - as a side note...
  39. R

    Techniques of Integration [need feedback]

    {I wrote this a while ago, thought i would share. I know it's not complete, far from complete actually, but if there's enough interest I'll finish it in notime...heak i might even write more expand the index.} INDEX TECHNIQUES OF INTEGRATION 1)Direct Use of Formula 2)Numerical Integration...
  40. C

    Amplifier negitive feedback capacitor and resistor in paralell

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  41. B

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  42. daniel_i_l

    Designing a Simple Circuit - Ask for Feedback!

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  43. P

    Black Hole Brief: Seeking Feedback

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  44. M

    Root Locus of Unity Feedback Transfer Function: Find K Range for Stability

    I want a MATLAB code to draw the root locus for a characteristic equation of a transfer function of unity feedback, also what is the range of K that keeps the system stable , here is the characteristic equation: s^5+600s^4+50000s^3+ks^2+24ks+80k=0 please help, thanks in previous
  45. W

    Seeking Peer-Reviewed Studies of Water Vapor Feedback

    One of the key factors in determining the climate sensitivity to the increasing atmospheric concentration of CO2 and other long lived greenhouse gases is the response of water vapor to the relatively small warming induced by these gases. Climate models produce a strong signal of positive water...
  46. M

    What Is the Role of an Integrator in a Differential Amplifier's Feedback Path?

    Hello all I have come across a circuit of a standard differential amplifier with an integrator in one of the feedback paths. I have no idea what its function is. I suppose some sort of frequency gain discrimination Any ideas? Matheinste
  47. P

    Differential Equation - Proof - Feedback.

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  48. N

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  49. A

    Three Essays, will anyone help me read and give feedback?

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  50. V

    Nuclear Reactor Feedback System

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