Three identical amplifiers having Avoc 20 Ri 2k and Ro 8k

Three identical amplifiers having A_voc = 20, R_i = 2k and R_o = 8k are cascaded. Find the input resistance, the open-circuit voltage gain, and the output resistance of the cascade.

Solution

open circuit voltage gain=A1*A2*A3=20*20*20=8000 since A1=A2=A3=20

input reistance =2K0hms Since input reistance of a cascade amplifier is the input impedance of first stage.

output resistance=8K0hms Since output reistance of a cascade amplifier is the output impedance of final or third stage.