Q. Explain the high-frequency response of FET amplifier?

 The analysis for the high frequency response of the FET amplifier is almost the same as that of the BJT amplifier. The FET amplifiers are interceded and wiring capacitances that will determine the high frequency characteristics of the amplifier. The capacitors C(6) and C(7) typically vary from 0.1 to 10 pF, while the capacitance C(8) usually vary from a bit higher range from 0.1 to 1 pF. Since the network is an inverting amplifier, a Miller effect capacitance will appear in the high frequency ac equivalent network. At high frequencies, Ci will approach a short circuit equivalent network and Vgs will drop in value and reduces the overall gain. At the frequencies where Co approaches its short circuit equivalent, the parallel output voltage Vo will drop in magnitude.

R(th) o = R (4) || R (5)

C_o = C (5) + C (8) + Cn,

C_n = ( 1 - (1/A)) * C(7)