Question 12.Consider the two-stage amplifier shown in Figure 1. Assume G = 2 mA/V. Find the value of the input and output resistance (in KΩ). Find the voltage gain of the amplifier (v_o/v_i) and the current gain (i_o/i_i).

Answer 12.

The input resistance is Vi/i_i= 35 K

To get the out resistance, turn of the source and plug in a test source, we get that Vt/i_t= 24 K

Vz/Vi= 20 x (60/80)

Vo/V₂= G x 24/44 x 20

Vo/V₂ x Vz/Vi= 20 x (60/80) x 2 x 24/44 x 20= 327.27 V/V

I₀/i_i= (V₀/R₀) / (V_i/ R_i) = V₀/V_i x R_i/R₀= 327.27 x 35/20= 572.7