# FET amplifier (Av=?)

How to find Vo of this pi model of FET amplifier? I have to find voltage amplification (Av=Vo/Vi) of this circuit and output resistance Ro, so I need to find the Vo voltage. I found the expression for current id, but I don't know how to express Vo. Could you please help? Thanks in advance.

(id-gm1Vgs1)rd1 + idRs1 + (id-gm2Vgs2)rd2 + idRs2=0

(id -gm1(Vi-idRs1))rd1 + idRs1 + (id-gm2(Vi-idRs2))rd2 +idRs2=0

• Also, I believe that in your small-signal equivalent circuit, your transconductance $g_{m1}V_{gs1}$ is pointed the wrong way. – Sven B Jan 26 '18 at 8:44