Questions tagged [negative-feedback]
The negative-feedback tag has no usage guidance.
196 questions
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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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Negative feedback divider calculation for NE5532
I have this "Switched Gain" circuit from Douglas Self's book.
I want to implement the same topology but with different gain in decibels: 0 dB, 3 dB, 6 dB and 12 dB.
I need a method/formula ...
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Op-amp output as gate voltage to MOSFET
As I understand it, the MOSFET here provides negative feedback to the closed-loop op-amp configuration. Hence, Vout2 = 1 V.
Thus, the current through NMOS = Id = 1 mA. So Vout1 = 5 - (RD·Id). Then ...
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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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Using an op-amp in an unusual configuration with (inverted) negative feedback to the non-inverting input
Here is a question for those who understand unusual, non-conventional op-amp configurations.
Is there any reason an op-amp can't be configured with an input going to the inverting input, and the ...
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None-inverting op-amp must zero output, why not?
simulate this circuit – Schematic created using CircuitLab
In this circuit, the input is continually summing with its negative through negative feedback, so it must become zero on the output. ...
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Determining the output impedance of a part of a circuit with negative feedback
I designed an active discrete baxandall volume control for my project.
simulate this circuit – Schematic created using CircuitLab
R*(a-1) and R*(a) are supposed to be a potentiometer, a being ...
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Closed Loop Transfer Function For Negative Feedback Circuit
I have the following circuit diagram
I understand the open loop circuit (H1H2H3H4) and I also understand the negative feedbacks H1H2H6 , H3H4H5 and H2H3H7, but I can't figure it out why the ...
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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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How can negative feedback reduce distortion if A*beta>>1?
I have read that negative feedback reduces distortion (frequency, amplitude, phase) because if \$A \times beta >>1\$ the transfer gain will be \$(A/(1+A*beta)) = A/A \times beta=1/beta\$. Which ...
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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 is the purpose of a negative feedback resistor in a schmitt trigger?
This schmitt trigger is used with an integrator to create a triangle/square wave oscillator but R5 has been added to the typical inverting schmitt trigger topology. I know that in simulation, this ...
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Feedback amplifiers and their corresponding system block diagrams
I'm a newbie in analogue circuits. I find it so confusing analyzing feedback amplifiers.
The typical feedback systems introduced in textbooks is shown below. The input signal \$X\$ is connected to a ...
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How can we confirm whether the op-amp has -ve feedback? [duplicate]
Many text books show an op-amp will have negative feedback when o/p is connected back to -ve input through some discretes and under such condition V+=V- is satisfied for op-amp input terminals.
In the ...
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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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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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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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Negative feedback in collecter-to-base bias BJT circuit
I'd like to calculate the 'feedback factor', \$\gamma\$, for the following simple amplifier. By definition of \$\gamma\$, the base voltage is \$V_\text{i}-\gamma V_\text{o}\$, where \$V_\text{i}\$ is ...
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Methods to measure output variable in a feedback system
\$R(t)\$ is reference signal, \$U\$ is controlled input, \$Y\$ is output of the plant, Ts=1 s is sampling time (i.e. after each 1 sec output and reference is compared) and input output relation of 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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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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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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Confusion regarding signal amplifier
Can anyone explain to me why the node voltage between the collector of Q1 and R1 have its signal amplified while for Q2, the node voltage at R3 and emitter does not have its signal amplified? I read ...
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Output resistance in negative feedback
I was studying negative feedback in voltage amplifiers. I found this on Wikipedia for calculating input resistance as shown below.
Following the similar method, I tried to calculate the output ...
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Irregular common emitter amplifier design
Would anyone know of any merits (or demerits) to the common emitter amplifier represented in Figure 1 in comparison to one of a regular pattern (Figure 2)? Thanks.
(The 'DS548' transistor in Figure 1 ...
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I don't understand how this current limiter works [closed]
This circuit is supposed to be a current limiter but I don't understand why:
simulate this circuit – Schematic created using CircuitLab
There is positive feedback between the output and the ...
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function of GND pin in voltage regulators [closed]
In a voltage regulator what is the function of the GND pin?I thought it was to create a reference voltage for the input/output but I have seen it being fed from the output of the voltage regulator ...
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OpAmp with common-mode voltages and zero feedback current
Circuit A is a classic non-inverting amplifier with a common-mode DC voltage 1 V to both its inverting and non-inverting input. Since 1 V has to appear at the inverting input, there is no voltage drop ...
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Op-amp with BJT circuit problem
I'm studying for EE final exam
First Question: what is the current through the red LED?
I have been working on this problem. So far, what i got is that with 5V come in the non inverting input of the ...
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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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In a negative feedback loop, why does increase in v_out lead to increase in v-?
I hope this is the right place to ask this question. (Please let me know if there's a better place to ask this.)
Basically, I'm quite confused about how we check if we have a negative feedback loop.
...
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Understanding Negative feedback loop circuit with an Ideal Op-Amp [duplicate]
The following is given as an example of a negative feedback loop in my textbook, note that the op amp is assumed to be ideal.
However I do not seem to get the logic behind this acting as a negative ...
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Understanding Negative feedback loop circuit with an Ideal Op-Amp
The following is given as an example of a negative feedback loop in my textbook, note that the op-amp is assumed to be ideal.
However I do not seem to understand the logic behind this acting as a ...
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What's the intuition for reading transistor/resistor circuits?
The below circuit supposedly provides constant current to an LED. I tested using everycircuit.com and that seems correct (used R = 70 ohm for example).
What's a step by step way of thinking about the ...
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Negative feedback gain sensitivity
What happens to the gain sensitivity of negative feedback system due to fractional change in open loop gain when feedback gain His about 0.01-0.05.
Here's my work:
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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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Understanding the biasing of a transistor with negative feedback
I am trying to understand the following circuit.
However, I don't understand this step in the accompanying explanation:
"A transistor with a large gain will cause a large voltage drop over the ...
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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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Feedback topologies advantages [closed]
We have 4 negative feedback topologies;series-shunt, series-series, shunt-shunt, shunt-series. I'd like to know something where we use these topologies. What are advantages compared to their each ...
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BJT or MOS negative feedback analysis
I am looking for a resource that includes analysis of feedback circuits. I have found something on sedra smith microelectronic circuits but not enough for me. Could you suggest me some resource ? It ...
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BJT amplifier with differential input and negative feedback - Open loop analysis
I am analysing the amplifier circuit drawn in the Art of Electronics 3rd edition (p. 121) and, while I follow the analysis presented and understand all the calculations in the text, I encountered an ...
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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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Transimpedance Topology - from block diagram to schematic
As I work through learning the four topologies of negative feedback, I can't seem to figure out the transimpedance amplifier.
As far as I understand it, I need to consider my input as a current ...
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Voltage-voltage Feedback and common-collector analysis?
(This question is related to this one here, where I attempted to understand how the discrete component values in a negative feedback amplifier are represented by the closed-loop gain and feedback ...
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Negative feedback from block diagram to circuit components
I can read and understand the block diagrams which show the internal amplifier and the feedback network and I can read and understand the schematics of several single-BJT amplifier circuits, but I ...
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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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What is the feedback network of this negative feedback amplifier?
I'm working through this handout Feedback In Amplifiers and learning how to visualize simple transistor circuits and their negative feedback. I'm perplexed by the example given for current-shunt ...
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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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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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