Hi guys, in the simple fixed-bias amplifier shown Here
with its equivalent circuit,
Why is the input voltage Vi equal to the gate-to-source voltage Vgs when we find the gain Av=Vo/Vi= (-gm*Vgs*(rd||Rd))/Vi, so Vgs=Vi and then Av will be =-gm(rd||Rd) as Vgs and Vi cancel each other???
Previously Vgs was equal to Vgg because there is no current the gate, but after we short circuited the sources and the capacitors to draw the equivalent circuit, Vi became = Vgs.
If it's like that, then we can say that Vi=Vgs=Gdd which is DC not AC?
Thnx very much
with its equivalent circuit,
Why is the input voltage Vi equal to the gate-to-source voltage Vgs when we find the gain Av=Vo/Vi= (-gm*Vgs*(rd||Rd))/Vi, so Vgs=Vi and then Av will be =-gm(rd||Rd) as Vgs and Vi cancel each other???
Previously Vgs was equal to Vgg because there is no current the gate, but after we short circuited the sources and the capacitors to draw the equivalent circuit, Vi became = Vgs.
If it's like that, then we can say that Vi=Vgs=Gdd which is DC not AC?
Thnx very much