q what the voltage gains in the fet amplifier for

Question

Q. What the voltage gains in the FET amplifier?

For common source

 Voltage gain=V_o/V_i = - µRd / Rd + rd

where µ is the amplification factor,Rd the drain resistance and rd the resistance series to the drain gate of FET.

For common drain

 Voltage gain = µR_sV_gd/(µ+1)R_s + r_d

where µ is the amplification factor,Rs the source resistance, V_gd the input voltage and rd the resistance in series to the drain.