In Reply to: Re: vgs1 and vgs2 posted by Jason on 09/27/03 at 2:44 AM:
Doesn't Ids1 = Ids2 = I1 have to be true? Where else can I1 current go? All gate currents are very small so assume they are zero for now.
Consider a graph of Ids v Vds for different Vgs for a MOSFET and assume Q1 and Q2 are operating in saturation. Its not really a big assumption. It just requires enough supply voltage. Then Vgs1 = Vgs2 because Q1 = Q2 and Ids1 = Ids2.
Now assume Q1 and Q2 are operating in the triode region. Vgs1 = Vgs2 for the same reason.