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Questions tagged [feedback]

Feedback is a process whereby information from an output of a signal is used (intentionally or unintentionally) to alter the input of the same signal. Commonly used in operational amplifiers. An everyday example is the high-pitched audio frequency heard when a microphone picks up audio from its own amplified output.

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Phase shift near saturation mitigation in input stage amplifier — How does this work, why does this work?

I'm trying to understand how this circuit works on the input stage to the 4192A Impedance Analyzer. Apologies for the quality... this is the best scan I could find. The design is furnished with the ...
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Output impedance of a series shunt feedback amplifier

I am trying to find the output impedance of a series shunt feedback amplifier by converting it to a two port network. I know the input impedance: Ri=ri*(1+A.β) But I dont know how I should find ...
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Feedback Circuit schematic to Control Theory block diagram?

I'm studying analog electronics circuit with feedback. I see that, during analysis, a useful abstraction over the schematic is the block diagram in control theory style, but I stuggle in deriving it ...
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107 views

Placement of feedback line on DC DC converter, before or after cap? (and dropout problem with LT8390)

I am using an LT8390 DC to DC converter, I have a highly inductive load and it is causing dips. The dips are shown here (and about a 6V drop for 7ms): I need to get rid of the dips, which I will ...
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53 views

Explanation on why there is no feedback in the circuit for higher voltages of input signal

simulate this circuit – Schematic created using CircuitLab I don't understand the reasoning behind the analysis of this circuit. The professor started by saying that if diodes D2 and D5 are ON ...
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52 views

Prevent current backfeed without power loss

I have a solar panel and an external power source feeding into a DC converter (U10) that are both used to feed a battery charger (U2): In a previous design I used 2 schottki diodes to prevent back ...
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64 views

Confusion of terminology for control systems

I am confused about the following definitions (if there are any): Reference input reference signal setpoint reference I don't understand specifically what they are referring to. Do they refer to ...
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39 views

total transfer function of a LTI System with feedback

I have calculated the transfer function of such systems many times, but now i feel like I`m going around in circles. I have drawn a few help-signals to help me solve it, but they are dependent of one ...
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101 views

loop gain, open loop gain of op amp in inverting configuration (feedback capacitor)

I was trying to understand the 2nd answer from this post here, with the circuit of the post shown below. The 2nd answer has equations including open loop gain I wasn't able to understand (1st ...
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67 views

In a closed loop system, when obtaining a bode plot why is the open loop transfer function used?

In a typical closed loop system, with G(s) as the forward function, and H(s) as the feedback function, why is the transfer function used to calculate the bode plot G(s)H(s) instead of G(s) / 1+G(s)H(s)...
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71 views

Differential gain of an op-amp and feedback

In an op-amp, we know from basic electronic courses that vo = A(v1 - v2) Assuming large differential gain and finite output, we get that (v1-v2) is very very small, ideally zero. In a university ...
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52 views

current source with op-amp+NMOS

this is a closed loop feed back circuit in order to make a precise current source. my first question is about R23. haw much it should be? i think it is better to just mounted a 0R resistor and ...
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56 views

feedback in switching voltage regulator

I need to design a switching voltage regulator, all parts work fine but I am having trouble figuring out the feedback, on the negative terminal of my comparator i have a triangular wave that cycles ...
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639 views

Deriving PI controller transfer function when input is reversed

I'm developing the compensator for the linear DC Bench Power Supply I'm designing. As I've come to deriving the transfer function for the op amp-based compensator, I realize I've been depending on a ...
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136 views

How to tune PID for a Y(t) = k*X(t) system?

Could I have your opinions on PID type selection? System description Here comes a very simple system: Output(t) = \$ k * (Input(t) + systemVariable(t)) \$. \$k\$ is constant and \$systemVariable(t)\$...
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How is this series series feedback topology forOPAMP?

This is stated as series series type of negative feedback but why. Whereas this one is series shunt topology
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Would a current feedback op-amp work well as a precision ground reference?

I've been looking into precision ground reference circuits to form ±5V rails from a 10V supply for a project I'm working on, and noticed that current feedback (CFB) op-amps have some desirable ...
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529 views

Unfiltered square-wave as feedback in class D amplifier

I found this little circuit that (ab)uses a TL494 SMPS PWM controller as PWM driver for a class D audio amplifier: (Source article @ Geekcircuits.com ) It uses the unfiltered, but constant amplitude ...
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Influence of NFB on the Gain of Amplifier

NFB is an acronym for negative feedback. Lets say that we have an amplifier with three stages: input (differential) stage followed by voltage amplification stage and output power stage. And we have a ...
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130 views

SEPIC converter working in BURST mode without having one

I designed a SEPIC using the LT3467 with coupled inductors. It supply 17V starting from a 12V input. On the simulator (LTSPICE) everything works, but on the test board there is a problem. With 70mA ...
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74 views

PI controller to drive a constant power source

So I have a load that needs constant power to maintain a specific temperature and this load changes over time. For this, I am using the design outlined in the following article: https://www....
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636 views

Determine polarity of feedback circuit

This is an example from Feedback chapter in Fundamentals of Microelectronics by Razavi. As you can see from the picture, the author gives two questions (why?). Could you check if my answers are ...
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260 views

How to model Texas Instruments UCC28700?

I'm using Multisim in an attempt to simulate a flyback supply design reference by Texas Instruments that makes use of a voltage controller - the UCC28700. Multisim has no SPICE model natively nor does ...
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188 views

PD control (PID without I) - Homework help

I've been given a system - x" = bx′ + kx + ru and I've been asked to rewrite it in the canonical form x' = AX + BU. I've got -- ...
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37 views

Three level PWM modulator circuit feedback simulation

I'm trying to design a three level PWM circuit with feedback and i'm struggling to understand the feedback aspect. The design is based on this design by Texas instruments and modified to suit three ...
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47 views

Amplitude control in a signal generator

A am working on an FPGA based function generator and I am aiming for max frequency to be higher than 10 MHz, hopefully 30 MHz. I have implemented most of the functionality except amplitude control. ...
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38 views

Negative feedback optical amplifier

Why the feedback network is necessary in this optical amplifier ? How the circuit would work without the feedback photodiode ?
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37 views

SEPIC vs. ZETA feedback

When I was reading through the RECOM book of knowledge DC-DC, I found out that the SEPIC converter has more chance of having resonance feedback than the ZETA converter. They mention that the SEPIC has ...
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34 views

What is the Correct method to find the poles and zeros expressions?

What is the Correct method to find the poles and zeros expressions ? This is a replica circuit method used to calculate loop gain, please only consider the above part. I used pspice to find the bode ...
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how C2 leads to negative feedback and C1 leads to positive feedback

C1 and C2 represent stray capacitances. I was told that C2 leads to negative feedback and C1 leads to positive feedback (pg 371 of Learning the Art of Electronics) and therefore C2 is good while C1 ...
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29 views

Breaking feedback resistor

I need to find the input/output impedances of this circuit (both open-loop and closed loop). I'm not sure how to deal with the Rf resistor as it lies in the middle. I was thinking to use the Miller ...
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68 views

Convention of closed loop gain in op-amp for inverting configuration

I tried to analyze real op-amp equations, in inverting and non-inverting configurations. I found a reference question here in which they were calculating exactly what I wanted to do: calculating the ...
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CSxCC stage, series-shunt feedback, identify sign of feedback

MY ANALISIS The stage is inverting x non inverting = non inverting. Shunt sampling since it perturbs the output current, Series mixing. Thus if a positive input voltage is applied, the output is ...
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Whats going on with my transimpedance amp?

Pulling my hair out with this design. I have the following design which was done using analog devices Photodiode Circuit Wizard tool so it should work. The current source in the schemeatic is the ...
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162 views

Buck/boost output voltage manipulation via feedback node

I'm designing an emitter follower circuit attached to the feedback node of a Buck/Boost SMPS in order to pull current out of the node and subsequently increase the output voltage by varying a DAC ...
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38 views

Calculating R, C & maximum input current of Oscillator Circuit

I have been trying all day to understand how either one of the values C1, Rs2 or the maximum input current can be initially calculated. I have worked out the equations however it seems that there is ...
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56 views

how can i pipeline feedback loop without functionality corruption?

I have a design in simulink that contain several arithmetic logics in a loop that limited the overall frequency of the design. how can i pipeline feedback loop without functionality corruption? I've ...
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78 views

Relation between crossover freqquency of loop gain and closed loop's corner frequency when feedback is not unity

In this Control Loop Cookbook from TI, in the red box the author said that the crossover frequency (indicated in figure 2) of the open-loop is same as 3dB down frequency or corner frequency of the ...
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57 views

What to do with PI feedback value

I've been studying and trying to implement a PI feedback controller for a BLDC. Right now, just to unit test the code for the PI controller, I'm driving two phases with a PWM signal on a MOSFET ...
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105 views

Solving for V+ using Vout

I have been instructed to use KVL/KCL on the following circuit to try and figure out an equation for V+: I've also been given a hint, saying that I can use the Vout from the previous time step of my ...
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64 views

Determining the phase margin of a negative series-shunt feedback circuit

I have been given a transfer function: \$H(s)={A_0\over (1+s/w_{p_1})(1+s/w_{p_2})} \$ With the condition that \$w_{p_1} << w_{p_2}\$ It's designed for this feedback circuit ...
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86 views

Identifying transistor feedback type

How can we identify the type of sampling and mixing in any transistor circuit with feedback ? I have tried to do that but I couldn't. Please help me with the type of feedback in the image I post. If I ...
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749 views

Determine if feedback is negative or positive?

Is there a way to know from how a circuit is designed that is has negative feedback or positive feedback. Here are some examples: Example 1: Example 2:
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43 views

Feedback analysis question

I am having difficulties understanding sections \$j-m\$ in the following question. What's meant by \$R_o,R_i\$? Input and output resistances or rather input/output resistances of feedback unit? If ...
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70 views

Determining open loop gain

What would be the gain of the A circuit (A unit in feedback) in the following circuit? First, what would be B? Merely the short connecting Vo and Q2?
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Unity negative feedback controller, why does Gain K go on the numerator of the transfer function

I have a system G(s). It has no zeroes, but some poles. When applying unity negative feedback, with a static gain K, why does K remain on the numerator of my transfer function T(s) which describes ...
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72 views

Implementing non-linear time delay

I have a feedback system including an OP-amp in comparator mode and a transistor, in present time it acts like a regulator, constantly limiting the current through the transistor to a certain value. ...
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695 views

Transistor based Voltage-Current Converter

For my last design question, Transistor current control with collector feedback, I want to add a NPN transistor between OpAmp and already shown transistor in common emitter mode. With new design, the ...
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241 views

Stability measurement of Operational Amplifier

All, I am trying to simulate as well as measure the stability of an op-amp with high gain (~50dB). The gain is necessary to boost a low level signal. I am struggling to understand if I am making ...
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125 views

How to get Voltage gain from a cascaded transformers?

I am solving a problem from Fundamentals of Electric Circuits Chapter 13, Problem 65. I know how to solve it using mesh analysis, on the other hand I am looking for a simpler method, so I am trying ...