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Homework Statement
two identical CS amplifiers connected in cascade. 1st stage fed with vsigand Rsig=100k ohm. load RL= 10k ohm connected to drain of 2nd stage. each MOSFET biased at ID = 0.25mA and VOV=0.25V. assume VA is very large. Each stage has RD=10k ohm.
a) sketch equivalent circuit of two-stage amplifier
b) find overall voltage gain Gv
Homework Equations
ID = (1/2)*kn*(VOV)2 <-- sat.
gm = knVOV
ro = |VA|/ID
GV=AV=-gm*RD || RL = -gm*RO
Vo = -(gmvgs)(RD||ro)
The Attempt at a Solution
i sketched the small signal circuit on paper but I'll probably show it later. solving for kn i get 8mA/V2. and gm=2mA/V. If VA is infinite then ro is infinite, and RO=ro||RD=RD. I get for 1st stage AVo1=GVo1=-20V.
To find the relationship for 2nd stage I did Vo1=Vi2=-(gmVi1)(RO) and Vo2=-(gmVi2)(RO)=(gm)2(RD||ro)2Vi2 then GVo2=Vo2/Vi2=400V. but is that right? I get a positive gain so I think i did it wrong.