Electronics and Communication Engineering - Analog Electronics - Discussion

4. 

An amplifier has input impedance of 4 kΩ and output impedance of 80 kΩ. It is used in negative feedback circuit with 10% feedback. If open loop gain is 90, the closed loop input and output impedances are

[A]. 40 kΩ and 8 kΩ respectively
[B]. 4 kΩ and 80 kΩ respectively
[C]. 0.4 kΩ and 800 kΩ respectively
[D]. 8 kΩ and 160 kΩ respectively

Answer: Option A

Explanation:

Closed loop input impedance = 4 (1 + 0.1 x 90) = 40 kΩ,

Closed loop Output impedance = = 8 kΩ.


Post your comments here:

Name *:

Email   : (optional)

» Your comments will be displayed only after manual approval.