The Stack Overflow podcast is back! Listen to an interview with our new CEO.

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.

Filter by
Sorted by
Tagged with
2
votes
2answers
206 views

What is the correct transfer function of a feedback loop if the summing amplifier has different input resistors?

Suppose I have a circuit below: simulate this circuit – Schematic created using CircuitLab I know the the transfer function of a negative feedback loop is: $$H(s)=\frac{H_1(s)}{1+H_1(s)H_2(s)}...
2
votes
3answers
3k views

RC phase shift oscillator : how to give positive feedback?

why is negative feedback given in a rc shift oscillator although a oscillator requires a positive feedback? as shown in this figure. And as shown here positive feedback is given by connecting the ...
2
votes
1answer
231 views

Unity-gain closed loop Miller OPAMP fails to follow the input after a few microseconds?

I implemented a Miller OPAMP. After I have checked it reaches the desired gain and swing, I put it into the simplest form of closed loop with UNITY negative feedback. The schematic is as follows: As ...
2
votes
1answer
191 views

How to Design a State Feedback Controller using an algorithm

I'm studying for an exam and am having a great amount of difficulty wrapping my head around this as I have minimal electrical engineering background, and my notes are confusing. I have read a few ...
2
votes
2answers
100 views

TL494/TL594 measure current with grounded load

Multiple examples of current limiting with TL494/TL594 suggest to use current sensing resistor between load(-) and GND. But I want load to be grounded. Can current sense resistor be placed above load(+...
2
votes
1answer
199 views

Transfer function of Op-Amp-Twin-T Filter

I have the following circuit and wanted to find out the transfer function of the whole circuit (which includes the non-ideal op-amp as well - modelled as a VCVS - H(S) is DC gain with some poles). I ...
2
votes
1answer
694 views

Barkhausen criteria: which is the overall effect if only the magnitude criterion is met?

I am going to try to explain better my question. Considering a simple control scheme made up of a forward-path amplification\$A\$ and a feedback-path frequency dependent attenuation \$\beta(j\omega)\$...
2
votes
1answer
129 views

Making a Radio Work

I am new at electronics and I decided to try my hand at making a radio. There seems to be a dearth of material online to actually explain practical radio construction. I built a radio given in the ...
2
votes
1answer
584 views

How can one seperate the negative feedback types one from another?

Like voltage shunt, voltage series, current shunt, current series. I can seperate them with opamps or box diagrams very well(its easy i guess) but when it comes to a point that we use real transistors ...
2
votes
1answer
375 views

Minimum feedback resistor Rf for given opamp ex: opa2134

i have a problem that needs solving; What is the minimum feedback resistor for modern opamps like opa2134 ? can it be 100 ohm? Im asking because in lt1028 datasheet its says it cant be <100ohm ...
2
votes
0answers
102 views

Help identifying component in SMPS

I have been working on a Schroff/Cherokee Europe PE1947/23B SMPS (circa 2004?) and have had trouble identifying a component within the circuit. This SMPS features the following outputs: +12v DC @ 8A ...
2
votes
1answer
143 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 ...
2
votes
1answer
456 views

Unrecognized and ignored parameters in LTspice while adding a Third-party model

I have tried to add a third party model to my LTspice program (2016 version) but when I run the simulation many errors show up. The model is made for PMOS and NMOS ( saved at the same link) Link of ...
2
votes
0answers
664 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 ...
2
votes
0answers
140 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)\$...
2
votes
3answers
187 views

Circuit for overdrive on vibrotactile motors

I have a school project where I have to create a haptic feedback wearable with vibrotactile motors. I have gotten the prototype ready which includes motors connected directly to the Raspberry Pi GPIO ...
1
vote
4answers
2k views

Negative feedback using op amps? [duplicate]

I never quite understood why negative feedback is more used than positive feedback. Using feedback makes it possible to adjust the gain, and thereby specify how much the input should be amplified. ...
1
vote
3answers
10k views

Why does the opamp output voltage saturate?

simulate this circuit – Schematic created using CircuitLab Vout = Vin (1 + R2/R1) According to this positive feedback topology - made an error here, it's Vout = Vin(-R2/R1) (edit) Now I ...
1
vote
2answers
497 views

What conditions could be expected to occur if one or both inputs of an op amp are left floating?

Question 1: Can an op amp work with both of the inputs floating? I assume that due to the input offset voltage if both the inputs are floating, the output would be +Vsat/-Vsat. Am I wrong? Question ...
1
vote
3answers
700 views

Why use an optocoupler with opto-driver instead of isolated amplifier using optocoupler for feedback

Why do so many feedback circuits rely on a optocoupler driver instead of using an isolated amplifier to directly transmit the feedback voltage to the switch controller?
1
vote
5answers
805 views

Why is the feedback of op-amp oscillators connected to inverting input instead of positive input

I'm new to the subject of oscillators and learned that sustained sinusoidal oscillations are made possible by positive or regenerative feedback. Is that right? If that's true then I can't quite grasp ...
1
vote
3answers
359 views

Help understanding negative feedback & bias design on audio amplifier

Please take a minute to look at the audio amplifier diagram below: In case it helps, the diagram comes from a do it yourself Velleman 7W Mono Aplifier (K4001) kit. The amplifier is based around the ...
1
vote
3answers
4k views

Modifications to 555 LED Fade Circuit

I was looking for a circuit to fade an LED on and off using no microcontrollers, and found this nice circuit: http://www.555-timer-circuits.com/up-down-fading-led.html it seems like exactly what I ...
1
vote
3answers
889 views

If I connect a schottky-diode to the DC converter output, why doesn't sense the voltage?

Why doesn't work the second version? If I try this version no voltage on the output. Why? I would like to make a reverse polarity protection, but the problem with the first version: in idle mode ...
1
vote
3answers
940 views

Closed loop output impedance

I'm currently reading the art of electronics 3rd edition and have stumbled upon this transistor power amplifier towards the end of chapter 2 (see picture below). The open loop (cutting point X from ...
1
vote
2answers
645 views

How do I take the larger of two analog signals?

I have two feedback signals. I want to create a circuit that outputs the larger of the two. I know I could do this with diodes, but I'm unwilling to accept the diode drops. I suspect some op amp ...
1
vote
2answers
634 views

What is meant by the break frequency of an op-amp?

1.Can someone explain me the break frequency of an op-amp and can an op amp have two or more break frequencies, if so how?
1
vote
3answers
101 views

I set up an amplifier (LF351) for a gain of 5.7, but it is saturating. Do I have to utilize the offset null pins?

simulate this circuit – Schematic created using CircuitLab The feedback network I am using is a voltage divider with 4.7K and a 1K resistor. The node after the 4.7K resistor is connected to the ...
1
vote
4answers
1k views

How does the output voltage of an Op-Amp swing to keep the inverting terminal at virtual ground in this circuit?

simulate this circuit – Schematic created using CircuitLab Vout should be -10 volts according to the voltage gain equation of inverting amplifier which is based on the rule of op amp that A is ...
1
vote
3answers
1k views

Why is a gyrator negative feedback?

Consider this circuit, this is a gyrator and acts like an inductor. Why when we analysis this circuit do we use assume negative feedback (i.e. the voltage at each input is the same). I thought that we ...
1
vote
5answers
868 views

Kinds of Feedback

"Feedback is a process in which information about the past or the present influences the same phenomenon in the present or future" I find the idea of feedback quite fascinating and i could realize ...
1
vote
3answers
249 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 ...
1
vote
2answers
110 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 ...
1
vote
4answers
340 views

Common emitter, o.p. set by feedback resistor

I am analyzing common emitter amplifier where operating point is set by feedback resistor between b-c. Voltage gain showed by symulator is much lower than (-)R2/R1 and input resistance is lower than ...
1
vote
3answers
179 views

Why can't the error in proportional control system be closed by increasing the gain?

Proportional control is a closed loop system in which error is fed back for reaching a particular value. However, if the error is too small, it can't make a correction. I think that this problem will ...
1
vote
3answers
1k views

Inverter Voltage Control - Stability Concerns

I have a voltage inverter that converts a 400VDC source into sine wave of 240VAC @ 50Hz. The inverter is based on a H-Bridge. The inverter works well but I'm struggling in understand how to control ...
1
vote
2answers
3k views

Individual Phase shift provided by Op-Amp in Closed loop configuration

When comparing the input and output of the Op Amp alone (Vid1-Vid2 and Vo and not Vsupply and Vo) in a closed loop configuration the phase shift is only 90 degrees? Why it is so? And the Simulation ...
1
vote
2answers
620 views

Differential Amplifier Transistor Pair

I have been dealing with these differential amplifiers for weeks now and still don't understand the basic principles of its operation and how should it be used inside an audio amplifier. I understand ...
1
vote
1answer
577 views

Are these BLDC waveforms making any sense?

I'm trying to drive a BLDC with a microcontroller, a discrete inverter and a sensorless network for feedback. Here's the model I'm using and what ultimatly is my PCBA: I'm driving this thing open ...
1
vote
1answer
298 views

FPGA design rules - Using a Module Output Register Value Internaly

I'm trying to optimize a verilog code and I found something that I don't feel it's correct. I found a module that has an output and it's using that output value as a condition in a case statement. ...
1
vote
3answers
283 views

Calculating the transresistance in a multistage voltage-shunt(shunt-shunt) feedback amplifier

I've been trying to analyze the following circuit using whatever books and resources I have to hand: simulate this circuit – Schematic created using CircuitLab I've identified the topology as ...
1
vote
2answers
252 views

Inverting Op-Amp Circuit Problem

I am trying solve the question shown in the picture below (I am assuming the switch is down in the picture, I can't tell) The equation that I am using is Vout/Vin = - Rf/Rin because there is ...
1
vote
1answer
627 views

beta of inverting opamp amplifier

I have doubt about beta of feedback loop of inverting amplifier. The expression for the feedback gain is : $$A_{cl} =\frac{A}{1 + A \cdot \beta}$$ what is value of beta here? and how do I reach to ...
1
vote
3answers
899 views

Push-pull amplifier oscillation

I try to build simple unitary push-pull amplifier which amplifies also DC. Here is a result of my work: Unfortunately high frequency oscillation effect occured due to strong negative feedback: My ...
1
vote
2answers
115 views

Big loop gain vs. big bandwidth

If one was looking for an audio amplifier of high quality, with very low distortion, which one of these two options would be better? Large loop gain (i.e. \$af\$) but small open loop bandwidth Small ...
1
vote
1answer
412 views

Speakerphones…no feedback…how do they do it?

I'm working with a factory on a speakerphone type of product but am getting feedback. We are using full-duplex. This is what we are seeing/hearing: User A talks into unit A Unit B's speaker plays ...
1
vote
2answers
261 views

How do the positive feedback increase the gain of a regenerative receiver?

I know that you adjust the positive feedback just below oscillation. But how can this result in a higher gain? The feedback would not just compensate the resistive loss in the tank circuit and thus ...
1
vote
1answer
551 views

Why are G and H used for feedback block diagrams?

The symbols \$G\$ and \$H\$ are typically used for the forward gain and feedback fraction in negative feedback block diagrams like this: The choice of \$G\$ is, I suppose, an obvious one, meant to be ...
1
vote
1answer
884 views

Efficient Single Phase Motor Speed Control

Usually triac based speed control vary the phase angle of firing to reduce the amount of power goes in to motor, and hence control its speed. this is not very efficient method, also it may not be good ...
1
vote
1answer
164 views

Generating pseudo-random numbers with restricted hardware

I have a need to generate a 448-bit value that appears random, for use in a test circuit. The "randomness" of the values is not overly important; the size of the generator hardware is. I am using an ...