Questions tagged [negative-feedback]
The negative-feedback tag has no usage guidance.
188
questions
5
votes
7
answers
900
views
Infinite output impedance in amplifier, instead of 0?
The question asks: "Exercise 14.5 Assume an ideal op amp and use the summing-point constraint to find an expression for the output current io in the circuit of Figure 14.14. Also find the input ...
- 111
3
votes
2
answers
210
views
+200
How are opamp node voltages being set in the following circuit and what is the use of the diode configuration?
I am using a PCB which has the following opamp configuration implemented. It's supposed to be a precision buffer for the source V3. I accidentally connected the source V4 as well and observed strange ...
3
votes
4
answers
287
views
I need help to identify the negative feedback loop in a hysteresis comparator
Can anyone help me identify where the negative feedback path is?
I want to determine the feedback factors for both negative and positive feedback, but it's not clear to me where the negative feedback ...
- 240
0
votes
1
answer
62
views
Why input signal of negative feedback amplifier is Vs - Vf?
The block diagram below is from my textbook. I don't understand why the input voltage Vi = Vs - Vf. Take an example as the image with numbers on it, I know its not correct in reality but just assume ...
- 11
2
votes
3
answers
239
views
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 ...
4
votes
5
answers
966
views
Unity Gain Amplifier Purpose
In layman terms, what is the main use and purpose of unity gain amplifiers? I am reading that it is used to "buffer high impedance sources" but I'm unsure what this means practically.
- 41
0
votes
1
answer
60
views
Input/Output Impedance for ALI
Consider these circuits from Paul Horowitz "Traité de l'electronique" page.238:
I want to derive the expressions they made for \$ Z_e, Z_s \$ for both circuits:
So I think the op amp is ...
7
votes
7
answers
1k
views
Negative feedback amplifier
The following circuit diagram is from a book on electronic circuits. The Current source \$I_s\$ is driver of the amplifier. It was written that this amplifier has negative feedback. It seems that if ...
- 701
0
votes
1
answer
73
views
About stability in system with loop gain AB>1 in negative feedback
I have been reading about stability and feedback systems, and a very silly issue has appeared.
We can describe a negative feedback system as what can be seen in the following picture:
Image source: ...
4
votes
4
answers
645
views
How to prevent this op-amp from railing
I have the following circuit:
An input that can go negative (+/-5 V sine wave), and two inverting op-amps. The second op-amp is "current buffered" and is driving the base of a BJT.
Here is ...
- 395
0
votes
0
answers
48
views
What are the necessary conditions to prevent latch-up problem for Oscillators?
In his chapter on oscillator design, Razavi discusses the issue of latch-up and proposes several methods to eliminate it. However, he doesn't provide explanations for these methods. Could anyone ...
- 113
1
vote
2
answers
176
views
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 ...
- 907
0
votes
1
answer
45
views
The influence of negative feedback on input resistance and bandwidth
I'm interested in how negative feedback affects bandwidth and the cutoff frequency.
Is the cutoff frequency always increased by (1-Ab) times?
fg_r = fgo*(1-Ab)?
Does the same apply to input resistance?...
3
votes
1
answer
100
views
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 ...
2
votes
2
answers
108
views
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 ...
- 439