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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20 views

Feedback network of transconductance amplifier with capacitor

simulate this circuit – Schematic created using CircuitLab How do I work on circuits that have capacitors as part of their feedback network? How can I calculate the feedback factor of the above ...
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50 views

Flyback primary side control

I read the LT3573's datasheet, I have some questions would like to ask. Based on this block diagram, 1.) What's the main function of the below circuit (red circle). 2.) If I need to detect the output ...
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134 views

Feedback network of three stage voltage amplifier

simulate this circuit – Schematic created using CircuitLab What is the feedback network in the above circuit? Is it just R4? My initial thought was that it is the parallel combination of R4 with ...
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43 views

Fully Differential Amplifier With Common Mode Feedback Network

I need to design the following circuit in a way that can provide a gain of 1000 and also has a power dissipation of 1.8 mW which, according to my calculations, results in a branch current of 250 μA. I'...
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60 views

Switching voltage regulator - exceeding output voltage limits

I have been designing a digitally adjustable step-down voltage regulator. Mainly because of the availability and price I chose: MCP1612-ADJI/MS I followed the datasheet and created the following ...
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18 views

System level behavioral model for PSSR of a switching regulator

In a design I have a switching regulator (buck for the sake of my example). The switching frequency is much higher than the frequency range of interest and can be safely ignored. However, the input ...
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Quick state feedback controller question

If two estimators where used in a state feedback system, one with error dynamics poles at -10 and -9 and another one at -80 and -90. Which system will give you a better overall performance?
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179 views

Positive feedback in Op-Amp Oscillators

Is positive feedback necessary in op-amp oscillators? Can you make one using negative feedback?
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59 views

Bode's Method of Feedback Analysis for Multiple Loops

I'm studying Chapter 8.6 of Razavi's Analog IC Design textbook (Bode's Analysis of Feedback Circuits). Bode's method provides a way of simplifying feedback analysis by replacing one dependent source (...
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82 views

What is meant by "Kelvin connected to capacitor" in layout terms?

In the MPS5496 PMIC layout guidelines on page 37, they mentioned that you should connect the feedback pins to the buck output capacitor "kelvin connected." What does that mean? Can anyone ...
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3answers
409 views

Class AB power amplifier from "Electronic Devices" by Thomas L. Floyd

I am an electronics engineer. I work as an industrial automation engineer in industry. As an electronics engineer, I love amplifiers and other stuff. I was reading Electronic Devices by Thomas L. ...
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77 views

Single-loop (PID) vs Dual-loop (i.e P-PI) servo position controllers difference?

I am wondering why the servo position loops are mostly dual-loop consisting of position and velocity loops while the position can be controller by using only the position PID controller. I am aware ...
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65 views

What is the function of emitter biasing of a transistor?

I have been reading about transistor biasing to counteract inaccuracies in transistor manufacture, add stability etc. One circuit I can't see the benefit in, which is diagrammed in the datasheet for ...
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48 views

How to control voltage using PID when driving SCR?

I am designing a scr based digital battery charger for the first time and have successfully driven scr to provide 110V-DC from a 140V singe-phase transformer. 2 SCR-diode combination forms full bridge ...
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108 views

Designing a small footprint DC/DC converter

This is my first time diving into DC/DC converters, so I'm learning a lot of new information and am aware that I may miss some important details. I'm hoping that others with more experience could ...
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1answer
83 views

What is the difference in these feedback configurations

In both these cases, the feedback remains the same hence the relation between input and output must be the same. However, if I want to analyse the closed loop stability, will the additional \$K(s)\$ ...
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4answers
312 views

Why is the output of an Op-Amp given by the open loop gain multiplied by the input differential voltage

When designing op-amps at the transistor level, the op-amp output is given by: vout = Aol(vinp - vinm) where vout, vinp and vinm are small signal changes in the output and input voltages. How come ...
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522 views

How does a unity gain buffer work?

Say we slow down time to a crawl, and turn on a power source connected to a unity gain buffer. Initially, the non-inverting input receives the signal and the inverting input receives nothing, so the ...
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1answer
26 views

Proportional gain with DC offset in LED driver circuit saturates output

I have a negative feedback loop with \$K_P = 10\$ for a LED driver circuit: I've used \$R_{fb} = 9k\$ and another resistor from the LED to the negative terminal of \$1k\$ in order to get a ...
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1answer
117 views

Range of feedback resistor value in non-inverting op amp

Is there any limitation for the range of the feedback resistor in a non-inverting circuit? What happens if I choose feedback resistor very high or very low? What is wrong with choosing a 10M ohm ...
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1answer
54 views

Do I need to regulate the output of a forward converter?

I'd like to know if a forward converter will maintain a nominal output on the secondary side. For example if I wind a powdered iron toroidal core with 1:10 turns ratio, the 1 being the primary, and I'...
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1answer
113 views

Common Collector Colpitts Oscillator - Feedback analysis

I am a student working on a project where we are using CC Colpitts oscillators as local oscillators. We've chosen the above values based on the condition gm > w02C1C2RL,series, which for the given ...
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142 views

How to set up an LTSPICE test bench for Common Mode Feedback Loop Stability

Suppose we are given a fully differential (low voltage single supply) op amp with common mode feedback. It is common knowledge to break the loop in order to measure open loop ac performance for loop ...
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2answers
173 views

Solve opamp with feedback without using virtual ground

Can we solve this circuit without using virtual ground or not? I attempted to calculate the feedback voltage by division of voltage in \$R_f\$ and \$R_{\text{in}}\$ but is \$V_f\$ equal to: $$(V_o - ...
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Why does input DC supply gets short circuited when operational amplifier is connected at the output of LLC resonant converter?

Following is the block diagram of LLC resonant converter, more clear circuit can be found here. This is an LLC resonant converter which produces 250V across RL with 50V at input without any issue. ...
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39 views

Converting dry contact to momentary switch with feedback [closed]

I need to adapt a fan that is turned on/off with an SPST momentary switch to also work with a dry contact. Additionally, I need to ensure that the desired fan state is reached when the dry contact ...
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1answer
79 views

Feedback Topology - MOSFET in feedback network

i have the following circuit: The feedback network consists of M4, which is biased in triode region. I know the concept behind Feedback Topology and the differences, but I can't figure out why this ...
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100 views

Anti integral windup method for analog integrator

I have found the following topology for an integrator/lowpass filter in a feedback system in an existing circuit . I know that the transistors act somehow as a limit of the amplifier, but I am not ...
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1answer
162 views

Preventing op-amp outputs from affecting one another

I built this op-amp circuit that takes in 4 inputs and outputs 3 sums by using op-amp adder and difference circuits to achieve a gain of 2x. In a simplified circuit, I boiled it down to the bare op-...
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1answer
80 views

TL494 error amplifier pin maximum voltage input

I'm designing a 60V SMPD for my CNC milling machine using a TL494. I've have successfully driven the gate drive transformer which can in turn drive the MOSFETs. I am able to get 60 up to 70V output ...
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61 views

Is there a chance that a DC/DC controller was damaged when a bad feedback network caused its output to exceed its absolute max limit?

I'm currently debugging an issue with a DC/DC controller. The part is a LTC3833. It turns out that the engineer who was working on this accidentally pointed to incorrect part numbers for the passive ...
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1answer
66 views

Manipulating circuit into two-port network for feedback analysis

I am trying to apply two-port feedback analysis to a circuit similar to the one shown below. I can't represent the forward amplifier as a two-port network because the input signal and feedback signal ...
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3answers
300 views

Why can you define closed loop gain when return ratio approaches infinity like this?

This is from this lecture video. Please check the video link if you're not familiar with the terms. I can explain it but I think the video lecture is pretty good at it. Because the feedback amplifier ...
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55 views

What is the initial input used in a NOR gate for a reset-set latch?

What happens the moment the reset-set latch is switched on?
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77 views

NOR gate implemented with 2 relays, schematic with 2 NOR gates with feedback loop

You have two NOR gates here, on the left side highlighted in yellow and on the right hand side highlighted in pink. Each NOR gate is implemented using two relays. In the yellow NOR gate, what is the ...
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98 views

Why does this oscillator not work with a voltage less than 9 V?

By chance of my research and simulations and various tests, I found the diagram of an oscillator with strange behavior. All the oscillators (quasi) that I have encountered work whatever the supply ...
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3answers
156 views

Audio amplifier - input stage, negative feedback and current limit

I am reading Audio Power Amplifier Design by Douglas Self and have a couple of questions. With no input signal, (Q2 base = Q3 base = ~0V) no current Ivas should coming out of the long-tailed-pair (...
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3answers
72 views

Current Feedback/Sense Circuit

I am trying to understand the circuit from this datasheet so I can use it in a project. The issue I am having is how the current feedback works (circled below). OUT_IFB is the current feedback for the ...
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1answer
129 views

Add negative feedback to this 2-stage amplifier

I am designing this 350mW 2-stage amplifier. The amplifier has only a voltage amplification stage Q2 biased with a current source Q1+Q3, a buffer Q6 and an output stage Q4+Q5. The input will be an ...
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53 views

Current feedback amplifier

I was wondering whether is it ok to connect a current feedback amplifier (CFA) after the TIA stage to obtain high swing and large bandwidth. I am not sure how to connect the CFA after the TIA stage.
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91 views

Is there a formal definition of a loop (in stability context)?

The circuit below with multiple feedback loops is taken from this page. The page considers only two loops in order to calculate the overall loop gain T. Is that enough? Doesn't it have 4 loops ...
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why do we assume unity feedback system when designing a controller for a system? [duplicate]

why do we assume unity feedback system when designing a controller for a system? Please guide on this issue. It's urgent. Thanks!
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2answers
178 views

How to break the loops properly here to get exact loop gains?

I got the circuit with two feedback loops from this page. I'm trying to calculate the exact loop gain of each loop. However, I'm not sure how to break the loop properly so you can account for loading ...
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3answers
210 views

Why is unity feedback used?

Why is the unity feedback system used? This block diagram is for a 2 DOF ball balancing using a PID controller.
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49 views

Purpose of switch in transimpedance amplifier

The schematic below is for a piezoelectric sensor. For the transimpedance op-amp, what is the purpose of the switch (SW1)? To my understanding, when the switch is on the bandwidth is reduced by the ...
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83 views

Mathematically representation of two loops where one is much faster than the other

In this post, akellyirl wrote: As a rule of thumb for design simplicity, the \$G_2H_2\$ loop is designed to be stable with significantly higher bandwidth than the final loop bandwidth so that its ...
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488 views

Why does this block diagram and equation give the wrong result?

Assume that we have a postive feedback block diagram like this. You can derive the closed loop gain as in the image. If you replace the numbers with loop gain larger than one, you get a wrong result ...
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1answer
45 views

Implement a voltage feedback method to reduce the crosstalkin resistive matrix

I'm new in electronics and i want to develop a resistive matrix that is pressure sensitive. Right now, I have a 7x7 matrix and I'm implementing this using multiplexers, a reference resistor and an ...
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47 views

what is the open and closed loop function of this system?

i found this in the text book. i solved by: 1- found the closed loop function of just the part of B(p) and its "feedback", let's call it B'(p). 2- after that i did H(p) = A(p) / ( 1 + A(p) * ...
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53 views

How to design a buck converter with feedback?

I design a simple circuit activates fan when processor heats up and then control rotation speed. I got the idea to create a buck-mode step-down voltage converter. However, I would like stabilize ...

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