Feedback Definition and 249 Threads

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.

View More On Wikipedia.org
Recent contents Top users
  1. G

    How does negative feedback in an op-amp work conceptually.

    Consider an op-amp in which there is a DC voltage of 100mV for example applied to the non-inverting (positive) terminal of the op-amp and the negative terminal of the op-amp is connected to the output directly. Also take the voltage supplied to power the op-amp, Vcc, to be 15V and the gain, A...
  2. R

    Need some feedback on a variation of the [[D = V°(t) + 1/2(A)(t)^2]] formula

    Hello guys, hope everything is going well. Anyways, I was thinking recently about the forumla for finding the distance an object has traveled with a constant acceleration using the formula D = V°(t) + 1/2 (A)(t)2 So basically when thinking about this formula, I like to think about an...
  3. P

    What Are Common Feedback Mechanisms in Everyday Life?

    Homework Statement Identify 10 feedback systems that you encounter in your everyday environment. For each system, identify the sensing mechanism, actuation mechanism and control computation. Describe the uncertainty with respect to which the feedback system provides robustness and/or the...
  4. L

    Feedback Control Systems as an Elective

    Hey everyone, I am an undergraduate mechanical engineering major considering a EE feedback controls course as an upper division elective. I have taken ME Control Systems and am also the Lab Instructor for it this semester. I am familiar with signals, filters, sensors, controllers etc. My...
  5. B

    Is Feedback Resistors' Impact on Transistor Amplification Significant?

    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...
  6. 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...
  7. 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...
  8. 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...
  9. 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...
  10. 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...
  11. D

    Mathematical modeling of a feedback control system

    My system is a compound pendulum hinged at some distance from one end and have a propeller mounted dc motor at the other end. I wish to position the pendulum with the help of motor propeller system. I tried but i am unable to get a mathematical model for it. I am getting a non linear model...
  12. A

    Analyzing the Movement of a Bicycle (requesting feedback)

    As I watched a few cyclists zoom by today, I started thinking about the mechanics behind the motion of a bicycle. I will now run through the work I have done in analyzing it. Please tell me if I have made any glaring mistakes in my logic and let me know what you think. Purpose Evaluate the...
  13. B

    Self-Studying: Feedback Strategies for Students

    I'm sure there are many like myself who are self studiers: read the book, do the problems. Right now I'm working through Halliday, Resnick and Walker, Fundamentals of Physics, and doing all the odd problems because the answers are in the back of the book. I'm also watching the MIT OCW lectures...
  14. R

    Feedback on a sound controlled light circuit

    Hi guys, I need to design a circuit capable of activating a light if there's a sound source. Sound= Light on No sound at all = Light off Here's an attempt (see attachment). The AC voltage source is simulating an audio source. Then i converted it to DC so it could activate both...
  15. L

    Understanding Opamp Circuits with BJT Feedback

    I can't understand an opamp circuit whenever there is an active element in the feedback loop. For example, in the current monitor ckt(attached). I don't understand how it works. I can't figure out how the opamp offset and BJT gain would affect the output. This ckt is from national semi AN31.
  16. Y

    Difference Between Normal Feedback Controller and Robust Controller

    Hi all, If we misrepresent the Model of the system say we linearized the System Model or any parameter variations like friction, Temp etc. Will normal feedback takes care of the offset of the Model? I was confused with Robust Controller. What is it? and How effective is it than normal...
  17. 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...
  18. E

    Velocity feedback damping in aircraft

    Describe velocity feedback damping in relation to aircraft systems? my attempt at an answer: I know what damping is, and i know what velocity feedback is, I just can see how they fit together. I think it's something along the lines of; an auxilery power unit has a speed sensor...
  19. 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...
  20. S

    Is the Grandfather Paradox Truly a Paradox if Feedback is Considered?

    Why is the "Grandfather Paradox" considered a paradox? Feedback exists in other disciplines, so why not in physics? Isn't disallowing feedback in time akin to stating that a negative feedback system can never exist in nature? (And, yet, they obviously do!) Why not assume that, as in other...
  21. 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...
  22. 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...
  23. A

    Feedback in Electronics: Definition & Meaning

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

    Leó Szilárd invented a feedback protocol1

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

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

    Hello Say I'm reading a (scientific) book, and find all these small errors in it (typos and stuff, nothing serious). Is there anyone to send a list of all these errors, for the benefit of future printings? (does anyone care?) Thanks
  26. C

    BRS: Feedback Poll, Question A

    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...
  27. 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...
  28. G

    Strong negative feedback in Climate

    A concept for strong negative feedback in Climate? I have been following some of the more interesting concepts in climate model theories for a couple years. Svenmark's cosmic ray theory in "The Chilling Stars", Svensmark and Calder, is very interesting. Miskolczi's theory of strong...
  29. S

    Explaining Quasar Feedback for the Struggling

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

    Oscillation conditions: Feedback phase shift

    One of the conditions for oscillation is that the (regenerative) feedback loop must provide a 180 degree phase shift. This is due to the fact that, for a regenerative effect, the signal must undergo n*360 degrees phase shift: 180 from the amplifier and another 180 from the feedback network...
  31. 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...
  32. D

    Feedback topology (MOSFET Clapp oscillator)

    Homework Statement I have this schematic for a clapp oscillator (see "ClappwBias") which includes the DC biasing network. When broken up into feedback topology, I end up with something like "betanet", where the output is taken from the source of the MOSFET. Homework Equations...
  33. N

    Does Positive Feedback in Op-Amps Prevent Immediate Saturation?

    I'm just wondering, if an op-amp is connected in a positive feedback configuration, should the output not saturate immediately? Here is an example circuit i made in pspice along with its input/output curve (V12 has amp of 3v). http://img689.imageshack.us/img689/1286/posfeedback.png As...
  34. A

    Routh-Hurwitz Stability Criterion: Solving Feedback Control Systems Homework

    Homework Statement http://img24.imageshack.us/img24/9028/72841137.jpg Homework Equations Routh-Hurwitz Stability Criterion The Attempt at a Solution For first question, you just write the Routh Array, make sure that the first row is all positive and you get Kmax = 1. Simple enough How...
  35. B

    Using Relay Feedback to Tune PID Gains

    Homework Statement What is relay feedback? I have to use it to create an automatic tuner for the differential, integral, and proportional gains in a PID control. Homework Equations The Attempt at a Solution
  36. 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
  37. Andre

    The AGW climate feedback discussion

    As promised in the now closed CRU-hack thread, this is intended to show why I am convinced that the cause for global warming is overstated and that changes in use of fossil fuel and CO2 production will have little effect on climate. I will try and stick to the scientific method, no room for...
  38. S

    Time of Motion with Negative Feedback

    A block of mass m slides down an incline plane of length xL. The friction factor b is constant, where the friction force increases as a linear function of forward velocity v. This produces exponential motion. My problem in building an educational simulator is this, I want to compute the time...
  39. S

    What is feedback? what is the advantage of it?

    What is feedback? what is the advantages of it?
  40. 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...
  41. 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...
  42. 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...
  43. 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...
  44. C

    Amplifier negitive feedback capacitor and resistor in paralell

    ok so if we have an amplifier with direct negative feedback we have a voltage follower if we put a resistor between that inverting input pin and ground, we can do these things: if we put another resistor between the output and the inverting input we can adjust the gain if, instead, we...
  45. B

    Voltage feedback and current feedback.

    Looking at the equations for the gain of a common cathode tube amplifier with the cathode resistor unbypassed (though the question in general could apply to similar configurations with BJTs and FETs) I see that the gain of the amplifier is something like \frac{\mu R_{l}}{R_{p} + R_{k}(\mu +1) +...
  46. daniel_i_l

    Designing a Simple Circuit - Ask for Feedback!

    Hi, I started to design a simple circuit and want to ask you what you think about it. http://img152.imageshack.us/img152/8508/circuit.th.png Basically what I have is a motor that can be turned on with a switch and can run for 5 more seconds when the switched is turned off. The coil...
  47. P

    Black Hole Brief: Seeking Feedback

    Hi guys, I have a brief I wrote up about black holes and energy transfer across the event horizon. I want some feedback - which forum group should I put it in? Pete
  48. 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
  49. 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...
  50. 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
Back
Top