Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [negative-feedback]

162 questions
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4 answers

Illustrating op amp feedback without control theory

We are teaching op amps in a high school class, before calculus. So we can't use control theory to teach how op amps respond. All the same, I would like to have an intuitive explanation for how a feedback circuit works. Take the negative…
Dov
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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 flow of electrons in such a circuit? How can we…
JC123
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10
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2 answers

Another Failed Differential Amplifier

This is the circuit I made - designed it, calculated it, built it: simulate this circuit – Schematic created using CircuitLab Q1's and Q2's collector current was 5mA, while Q3's was 1mA. Sine wave at the input had 1Vpp at 1kHz. Negative feedback…
Keno
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8
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3 answers

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 on internet, the Vce of transistor must be biased…
chuackt
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8
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3 answers

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 is just a BC548.) (The diode in Figure 1 is just…
kene02
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8
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2 answers

White and Pink Noise Generator Circuit - Cryptic AC Analysis

The “Electronic Devices and Circuit Theory” book (by Boylestad, Nashelsky) gives a brief description of a random noise generator circuit at the end of “BJT AC Analysis” chapter. (Btw, exactly the same circuit appeared in the IET magazine, April…
RayX
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8
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3 answers

Operational Amplifier with mixed feedback

So, I came across this circuit in a test, it's regarding the operation of an op amp with multiple (positive and negative) feedback, the circuit is as follows: I was asked to evaluate the following statements about it: 1. Does the Operational…
Archer Fuyyr
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7
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3 answers

Why is inverting op-amp behaving like a low pass filter?

can anyone explain why this circuit behaves like a low pass filter despite having no capacitor in the feedback loop?
mwilliams25
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5 answers

Is transistor in cutoff?

In the following circuit, consider the op-amp to be ideal (gain = ∞ , input resistance = ∞) and transistor beta is 20 A/A Initially I was using virtual ground concept here but in the given answer transistor is in cutoff so voltage at -ve terminal is…
user29918
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3 answers

Highly Distorted Output of Class B Power Amplifier

This is the circuit I made: simulate this circuit – Schematic created using CircuitLab This simple circuit incorporates differential stage - VA (Voltage-amplification) stage - OPS (Output Power Stage). Open loop gain is high, closed loop gain is…
Keno
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6
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5 answers

Non-inverting op-amp

Why is resistor R1 connected to the inverting terminal of the op-amp in a non-inverting op-amp configuration? What will happen if we replace it with a short circuit?
Jina
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6
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4 answers

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 feedback connected to the non-inverting input through…
mr coffeeee
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6
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4 answers

What's the need for a small capacitor in the negative feedback parallel to a feedback resistor?

I have the following circuit: I think I understand pretty much all the aspects of it except for the small capacitor in the feedback. What is the need for it? Judging by the frequency of 1 MHz that is the inverse product of the capacitance and the…
Sergii
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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 across \$ R_i \$ and subsequently there cannot…
KMC
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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. During lecture, when checking whether this was…
norwegian_forest
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