# New impedance after feedback

tanaygupta2000
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.

Gordianus
How do input and output impedance change when you apply feedback? Have you studied that point?

Gold Member
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?

• berkeman
Gordianus
• berkeman
LvW
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?)