Common Source (CS) FET amplifier at high frequency-page-1

High frequency small signal model

                        V_gs = v_i

R_s reduces the gain of the amplifier although it improves bias stability.

Applying KCL at node D

(v_i - V_O) Y_gd – g_mv_i – V_O (Y_d + Y_ds + Y_L) = 0   Y_gd = jωC_gd

V_i (Y_gd - g_m) – V_O (Y_gd + Y_d + Y_ds + Y_L) = 0

For low frequency small signal model

[R_S = 0]

A_V = -g_mR_d’

Where R_d’ = R_d | | R_L

nput Impedance

Y_i = jωC_gs + jωC_gd (1- A_V)

C_i = C_gs + C_gd (1+g_mR_d’)      [ A_V = - g_mR_d’]

Miller’s Effect

Problem

Taking V_DD + v_e

I_D = -2.25 mA

V_DS = -10.5V

<< Prev | Next >>