Question

Consider a voltage series feedback network, where amplifier gain = 100, feedback factor = 5. For the basic amplifier, input voltage = 4V, input current=2mA. Find the input resistance of the network.

(a) 1.002kΩ

(b) 1002kΩ

(c) 2kΩ

(d) 2000kΩ

I had been asked this question in my homework.

This intriguing question comes from Feedback Connection Types in chapter General and Feedback Amplifiers of Analog Circuits

Answer 1

Correct answer is (b) 1002kΩ

To explain I would say: RI = VI/II = 4/2m = 2kΩ

RIF = RI(1+A.β) = 2k(1+500) = 1002kΩ.