What is the effect of feedback on input and output impedances?

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    Feedback Impedance
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Discussion Overview

The discussion revolves around the effects of feedback on input and output impedances in electrical circuits. Participants explore how feedback influences these impedances, the methods for measuring them, and the implications of specific feedback values on voltage gain.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant notes a change in voltage gain due to feedback but expresses uncertainty about determining the final values of input and output impedances.
  • Another participant asks how input and output impedances are affected by the application of feedback, indicating a need for further study on this aspect.
  • A participant inquires about the methods to measure input and output impedances and requests information necessary for these calculations, suggesting the importance of a schematic for clarity.
  • A link to a video is shared, possibly as a resource related to the topic, but its relevance is not discussed further.
  • One participant refers to a specific feedback value (βv = 0.1) and questions whether the resulting gain will be larger or smaller than the gain without feedback, implying a need for exploration of this relationship.
  • A comment suggests that answers to the original question can be found in textbooks, prompting a reflection on the participants' research efforts.

Areas of Agreement / Disagreement

The discussion contains multiple competing views and remains unresolved regarding the specific effects of feedback on input and output impedances, as well as the methods for measuring them.

Contextual Notes

Participants have not reached consensus on the methods for calculating or measuring impedances, and there are unresolved assumptions regarding the circuit configurations and feedback mechanisms involved.

Who May Find This Useful

This discussion may be useful for students and practitioners interested in electrical engineering, particularly those exploring feedback systems and impedance measurements in circuits.

tanaygupta2000
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Homework Statement
An amplifier has a voltage gain Av = 1000 , input impedance 1 kΩ and output impedance 500Ω A
fraction βv = 0.1 of the output voltage is fed back in the series in opposition to the input voltage. The
input and output impedance after the feedback are given respectively by the approximate values ?
Relevant Equations
A' = A/(1-βA)
I know that when the feedback is connected, the voltage gain changes by the above formula. But I don't know how to find final values of input and output impedances.
 
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How do input and output impedance change when you apply feedback? Have you studied that point?
 
How would you measure the input impedance (i.e. what information about this circuit do you need to calculate this)? How would you measure the output impedance?
Have you drawn a schematic of this circuit yet?
 
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You have mentioned a formula for the gain A´ with feedback ...when you insert the mentioned value βv = 0.1 , will the gain be larger or smaller than A (without feedback)? What do you expect ?

(By the way: An answer to your question can be found in each relevant textbook...did you already spend some time for searchnig?)
 

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