Questions tagged [negative-feedback]
The negative-feedback tag has no usage guidance.
196 questions
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How to break the feedback loop and add the loading?
I am trying to break the feedback loop of a fully differential amplifier and add the loading to the input and output:
I want to do this to take into account the loading of the feedback network on the ...
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Understanding of Dominant Pole Compensation
According to Miller Effect, within amplifying devices such as transistors that have inverting voltage gain higher that one, there should be increased input capacitance with increased voltage gain of ...
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Sensor datasheet shows op-amp circuit with capacitor to ground from inverting input. How does this work?
In the circuit above the inverting input feeds to ground through a capacitor.
The output should be a constant voltage used for reading into an ADC/taking a measurement.
A negative feedback op-amp ...
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Learning the Art of Electronics 9N.4 -- low-dropout voltage regulator
I have trouble understanding one circuit in section 9N.4 of the book "Learning the art of electronics" by Thomas C. Hayes. I attached a screenshot of that section below.
I understand the ...
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Ideal closed-loop gain derivation for negative feedback
Considering a negative feedback system, the closed-loop transfer function Af is given by:
where A is the open-loop transfer function and AB is the loop gain.
Every text I read says that if the ...
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Why can't the following configuration be considered negative feedback?
In the following circuit I have kept the resistor ratio such that beta factor of negative terminal (part of output will come on inverting terminal by voltage division), is higher than that of positive ...
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Identifying a multiple feedback op-amp circuit
I stumbled upon the circuit above, and am trying to understand what its frequency response would be. I just started learning about filters, but haven't come upon a multiple-feedback topology like this....
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Op-Amp output inconsistent with theory
I was just playing around with a few Op-Amp circuits, and suddenly got stuck on this simple one.
As the circuit shows, the Op-Amp output is connected to its non-inverting input terminal, so it should ...
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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 ...
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How to justify that op-amp 1 has negative feedback?
Op-amp 1 is topmost in the schematic below. I used the ideal amplifier method (using A until the end and then lim A->infinity) and also the virtual short method.
But I don't know if that's enough to ...
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Can negative feedback in an opamp circuit be applied to the noninverting terminal?
In figure 1, is the feedback regenerative in nature? If so, can I apply a virtual short to solve it?
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Gain of a negative feedback circuit (problem)
I am asked to find the gain A for this negative feedback circuit below:
(A: gain, G: all of the gain of the circuit, F: return ratio)
The simplified circuit above shows the gain A that I am trying to ...
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Negative feedback sustainability
If positive feedback makes output exponentially increase and cause instability in an opamp then why doesn't negative feedback make output extremely small and cause the system to collapse?
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Is there also equal voltage on the inputs of an op-amp with a capacitor in the feedback rather than a resistor?
It can be mathematically proven that when we have a resistor in the negative feedback of an op-amp, the input voltages in the inverting and non-inverting terminals get equal.
I'm wondering if we can ...
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Diode in feedback path of transistor (collector-base)?
This is the schematic for a fuzz circuit. Even knowing that the diode is probably what's providing the signal clipping, I still can't figure out how I'm supposed to analyze the circuit.
When V(...
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Op-amp amplifier feedback, offset
The following circuit is a non-inverting amplifier with a normal op-amp. I know how the "classic" one works: Vout/Vin = (R1+R2)/R2. However, there is a third resistor R3. As far as I know, it has ...
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Current Sensing with Op-Amp, do I need a shunt resistor in series with the load on the output?
Hi I am building a circuit to measure current draw from a load, I opted for a voltage follower with a transistor and a shunt in between, The transistor is needed to allow higher currents to flow ...
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Implementing negative feedback on a JFET amplifier
I have started designing and simulating a simple Jfet amplifier using LTSpice.
The circuit I have below seems fine, apart from too much gain for my needs (about 20x to much gain).
To fix this, I ...
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Contradiction between two circuit simulators in measuring open loop gain
I am implementing what I've learned over the past couple of days. This relates mainly to the simulation of a voltage regulator.
I built the (roughly) same circuit in both TINA TI and LTspice to ...
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Emitter Follower / Common Collector as Negative Feedback Amplifier
Background
From the wikipedia page on Common Collector Amplifiers there is paragraph describing how the circuit acts as a negative feedback amplifier
The circuit can be explained by viewing the ...
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Working out resistance for unknown BJT circuit
First of all, excuse me if this question is trivial or common, but I'm trying to essentially self-teach for an upcoming Analog Design exam, so I'm going through older problems that the professor had ...
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RL circuit as a feedback loop
As far as I know for a feedback loop ,
a sensor is required to reduce the effect of disturbances but
1.why a simple RL circuit has a feedback loop but it didn't contain any sensor , so
isn't sensing ...
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TL431 Loop Compensation
I'm trying to understand this material from C.Basso regarding TL431 compensation (Designing Compensators for the Control of Switching Power Supplies
If you refer to pg.110, there is one example ...
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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 ...
user141515
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Opamp + NPN and MOSFET in the feedback network, how to prevent oscillations
Background
The task is to add an electronic means to limit the power applied to an electric motor in an industrial setting. The operator normally controls the motor power through a lever that is ...
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RC filters in JFET negative feedback
I saw a useful answer about JEFT negative feedback here and so I thought I'd ask for some help too!!
I'm attempting to create a JFET gain stage that uses a filter in a negative feedback loop to boost ...
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What "was" input resistance of this voltage-voltage topology amplifier before feedback?
I'm slowly working my way through understanding negative feedback in simple BJT amplifiers. I'm studying this circuit here:
I read that one of the advantages to negative feedback in this topology is ...
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Voltage-divider bias common emitter calculations are yielding unexpected results
I performed an analysis on this voltage-divider-feedback common emitter. My result in simulation is relatively close, but doesn't quite check out. Where did I go wrong? I'm new to this and ...
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How do I perform ac analysis of common emitter with voltage divider feedback?
I'm working towards understanding voltage-shunt feedback. I'm about halfway there, and stuck. I am building a simple common emitter with voltage divider feedback.
I managed to get it biased to put ...
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Why is this digital output circuit non-linear to the load?
I'm simulating a DAC which puts out 0-20mA, but in practice, the output varies depending on the load of 300 ohm resistor. If I using a 1k ohm resistor, then I get a different output current.
If you ...
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How output is not zero if error is zero in control systems
In a classical negative control scheme where we have a plant and controller in series and no disturbance. The system is designed such a way to make output is equal to input no matter what problems ...
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Phase Margin and Transient Response Contradicting?
I am designing a forward converter that is supposed to work as a pre-regulator for a linear supply. The forward converter is supposed to be able to give output from 4V to 34V and 0 to 5A. While ...
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Linearity and speed tradeoff with closed-loop feedback
This article describes some tradeoffs involved with methods to increase an amplifier's linearity. One of the ways to increase a circuit's linearity is by applying negative feedback, which converts an ...
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Common emitter circuit - can't understand negative feedback
I have a problem with understanding how does the negative feedback of this circuit work.
In all books that I read it is said that "with the rise of temperature, collector current increases". Why is ...
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How do I analyze this negative feedback?
I'm working on understanding the four negative feedback topologies. My process has been to first analyze the circuit's dc and ac characteristics for quiescent current, gain, impedance, etc. Then, I ...
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How many / which electrodes should I use as input for an RLD (right leg drive)?
When reading through the datasheet of the ADS1298 (an analog Front-End for Biopotential Measurements) I noticed the schematic on page 42 (see below):
It is possible to select or deselect the positive ...
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Modeling first-order dynamics of a switching converter
I have created a simple, first-order model of a switching regulator in steady state (it's basically a transformer with a loss element). Its only parameters are desired output voltage \$V_o\$ and ...
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How does a capacitor-crystal-capacitor π-network produce a 180° phase shift in a Pierce Oscillator?
The Pierce Oscillator consists of an inverting amplifier, a crystal in parallel with a biasing resistor as well as two capacitors connected between the legs of the crystal and ground, as in the ...
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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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How do we explain the common-mode feedback in an intuitive way?
There are such beautiful circuit ideas that make you hold your breath and admire them silently. Such an idea is the common-mode feedback (CMFB) in fully differential amplifiers. I was not familiar ...
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Understanding negative feedback in an inverting op-amp
Below is a basic inverting op amp. I'm having trouble seeing the negative feedback operation.
simulate this circuit – Schematic created using CircuitLab
If I understand the "golden rules" of ...
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How does an op amp reach equilibrium?
It seems to me that if you try to solve for an Op-amps output (with negative feedback) discretely (i.e. iterating), you never reach equilibrium. Rather, you find the output moves further and further ...
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How to analyse this with nullor block?
The first is the schematics from NMOS4 with parasitic capacitance:
I recently read an article on how to analyse the circuit with The Nullor and Some Applications.
The equivalent nullor circuit. I am ...
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Analyzing current-series negative feedback using voltage gain confusion
(I posted a similar question that shows a better understanding of the circuit here.) I don't know if my reputation would suffer if I deleted this question.
I am learning the four negative feedback ...
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Diagnosing possible SMPS feedback loop failure
I work in a theatre and I'm looking for some guidance on how to solve an issue regarding a 24V power supply in one of my LED lights. The model is a Chauvet SlimPAR QUAD 12 IRC, to be exact, consisting ...
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How is loop gain related to the complete transfer function?
I am trying to understand how the loop gain of a system determines the stability of a complete system.
Loop gain is given by 1+GH where G is the forward transfer function (TF) and H is the feedback ...
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Please explain negative bias and "a stronger field to sweep carriers out of depletion"
I want to understand what a comment means, and I couldn't ask in a comment. In this question, someone asked why use an op-amp with a photodiode rather than just a resistor. The answers and comments ...
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Differential signalling with negative feedback
Does differential signalling always comes hand to hand with a negative feedback circuit?Else the 1s and 0s would be the same!because if we have ground in the inverting pin then the output voltage will ...
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Why is this the voltage gain formula in the two-stage feedback amplifier?
In Albert Malvino's "Electronic Principles", he said that in a well-designed two-stage feedback amplifier for small signal operation(picture below) , the voltage gain equals $$A_v=\frac{r_f} {r_e}+1$$
...
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Op - Amp: Linearity, Negative Feedback and Virtual Short
I need some explanations about Linearity, Negative Feedback and Virtual Short for an ideal Operational Amplifier.
Precisely, I have been always told that an operational amplifier with negative ...
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