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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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How does not using common-mode feedback drive my outputs to the rails?

Consider the following circuit in Fig 9.31 (a) Now, essentially, summarising the block of text, it seems that due to some mismatch between PMOS and NMOS devices or fluctuations in bias voltages, the ...
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52 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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782 views

How do I implement a feedback to keep the DC gain at zero for this conceptual passive filter?

Regarding an example passive LC ladder filter, when I sweep the source resistance, Rs, the filter characteristics changes as follows as expected: On the other hand, if I sweep the load resistance, ...
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114 views

Proportional Control Balance Beam

Bit of an unorthodox question I'm sure, but I'm making a balance beam (two rotors on either end of a see saw) with proportional control, and I can't seem to get it to balance at 0. The proportional ...
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82 views

Analog implementation of imaginary roots in a transfer function

I have a simple boost converter, and from multiple papers I've read through, a Type 3 Compensator is recommended. I designed one in Matlab/Simulink, and it reacts very quickly. The problem is, when I ...
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54 views

Why does adding a capacitor to the adjust pin of a voltage regulator improve PSRR?

When looking into the datasheet of an voltage regulator, they often recommend adding a capacitor from the ADJ pin to ground, to improve ripple rejection. It can also often lead to an significant ...
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29 views

Feedback Block Diagram Reduction

For this diagram reduction question, I thought pushing the summing junction to the left past the G1(s) is can be a solution but is it correct that pushing to number 2 then we can collapse the summing ...
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Interesting Op Amp issue

Good board - bottom view Good board - top view Bad board - bottom view Bad board - top view I am new here and mainly a hobbyist when it comes to electronics. I work more with electricity than ...
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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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40 views

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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42 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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1answer
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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78 views

What causes random ringing in my inverter?

I'm currently redesigning the inverter for driving my induction heater. While I've sorted out most problems I encountered I'm still struggling with the actual inverter. Picture 1 shows the waveform ...
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78 views

How to identify the circuit has negative feedback or positive feedback?

I am having difficulty in identifying whether feedback is negative or positive (i'm not talking about feedback topology) My teacher told that there is a method in which, after deactivating ...
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58 views

Differential amplifier with feedback resistor

In this circuit, if a resistor of 1 M\$\Omega\$ is connected between A and B, what is the effect on the stability of the quiescent point? The analysis I made led me to believe it would provide ...
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Reason for small-valued feedback resistors in low noise Op Amp

I am wondering why the feedback resistor values specified in the datasheet of the AD797 are so small. My understanding is that the low feedback resistances keep the noise small, but isn't it also not ...
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39 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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37 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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31 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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Avoid voltage feedback from laser psu to Arduino via pwm pin [closed]

I have been using GRBL software on arduino board for quite a while now, however the only issue I have is that the CO2 laser PSU kind of passes a small current back to the Arduino from its control pins,...
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Why is current controlled feedback faster than voltage controlled feedback in PWM controllers?

Looking at modern ICs, we prefer current control feedback over voltage control feedback, due to the speed of the feedback. Current control will react faster than voltage control. Here are 2 images, ...
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1answer
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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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33 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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1answer
48 views

How to break this multistage feedback amplifier to find loop gain Aβ ? (I'm using pspice)

by hand calculation I know that loop gain Aβ of this (current-current) circuit is 30, I tried to break this circuit and add Vtest to it , and setting input to zero but I didn't get a result that match ...
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Amount of feedback in an amplifier

Sometimes I read things like "This amplifier has 30dB of feedback", what figure is that refering to? the \$\beta\$ of the amplifier? or the loop gain \$1+A\beta \$? or the negative feedback factor \$\...
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37 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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2answers
169 views

Is static negative resistance practically available?

I learned that negative resistance (NR) could be simulated by involving active devices like op-amps and others. I'm interested in the static/absolute NR rather than the differential NR. My question is ...
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117 views

What is this NOR feedback loop in the AGC Cross Point Generator II?

This feedback loop looks similar to a LFSR, however there are no registers present. It looks to be some kind of oscillator. There seem to be three inputs to this component, ...
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131 views

Opamp with multiple feedback loops

I have been trying to figure out how the following circuit works and what it might be good for without any luck so far. What might the transfer function be? Is there a way that analysis can be ...
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Why do we get only one frequency as output in oscillators?

I am just into oscillators where I learned \$AB=1\$ for sustaining oscillations in positive feedback. Since \$A\$ and \$B\$ are both frequency-dependent, \$AB=1\$ is true only for a particular ...
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44 views

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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28 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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1answer
32 views

Find gain of this common-gate

I have a large circuit involving feedback as follows I am trying to find the closed-loop gain of this. Before I can do that, I need to find the open-loop gain. Thus, removing the feedback loop, M2 ...
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51 views

Why is the gain of feedback amplifier Vo/Vs?

Amplification = Output/Input Then the amplification of the feedback amplifier should be Vo/(Vs +- Vf) Here, Vf = feedback signal Vo = Output signal Vi = Input Signal and Vi = Vs +- Vf Vs = ...
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63 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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60 views

Active Integrator Parallel Capacitor in Feedback

I am designing an integrator circuit, looking to perform in the range of 10-10kHz - and I had a thought and I cant find any information online about it. For low frequencies of 10Hz, the reactance of ...
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95 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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1answer
123 views

Designing two stage CE amplifier with negative feedback [closed]

I'm trying to design two stage ce amplifier with negative feedback using 2n2222 transistors. The circuit must have certain voltage gain, Rin, Rout, Vcc, low and high frequency filter. This is the ...
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195 views

Inverting OpAmp with voltage divider in feedback loop

Last week I was looking for a programmable gain amplifier (PGA) with high gains (> 100V/V) and low noise. As far as I know most of the PGA integrated circuits out there are just (inverting) amplifier ...
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167 views

Feed-forward capacitor in SMPS feedback

I was looking at the TPS63700 DC-DC inverter datasheet and stumbled across the schematic below. It is a more or less usual buck-boost inverter topology schematic, except for the weird R4 and C3 ...
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1answer
45 views

VFA vs. CFA Compensation Capacitor Comparation

Here, I am referring to voltage-feedback amplifier (VFA) and current-feedback amplifier (CFA). A basic schematic is given below for each. I.) VFA II.) CFA I am curious about the position of ...
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1answer
98 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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1answer
74 views

Op amp with feedback

simulate this circuit – Schematic created using CircuitLab How to calculate Iout(current flowing through RL) of this circuit? All Resistors are of same value except the load resistor. Let the ...
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1answer
159 views

Need help choosing resistors for difference amplifier

In the circuit below I am trying to achieve 15.56 gain on IC2. The following combinations (in kOhms) are fairly close: 20/1.3 or 200/13 = 15.38 47/3 or 470/30 = 15.67 51/3.3 or 510/33 = 15.45 56/3.6 ...
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150 views

Buffer OPAMP feedback resistor

I am using an LT1630 as a buffer... I know its not the greatest OPAMP for the job because it has fairly Hi input current, but It has good DC characteristic, HI current drive, and rail to rail ...
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54 views

speed control loop percent error

I'm having trouble understanding the percent error from the following closed loop feedback equations. \$w =1\$ is the road grade change and \$r=65\$ is the speed control input, and given closed loop ...
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104 views

Operational amplifier and negative feedback

Let's consider an op-amp. In every book I've read till now, it is said that if we have: negative feedback finite output then we have: Vout = A * (v2 - v1) --> (v2 - v1) = Vout / A If A is very ...
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1k views

Non-inverting op-amp configuration with capacitor

I don't really get what is the purpose of the capacitor C1 which is connected in parallel with the feedback resistor. After my knowledge, if we modify the input signal frequency the over all gain will ...
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80 views

Feedback Error Equation

I am currently digging into some amplifier feedback analysis tools papers and literature. I found some "term" right at beginning of this topic that I don't quite understand. That is "Error equation of ...
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61 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)...