Re: Op-Amp
The output impedance of this opamp is (gm3ro3ro1 || gm5ro5ro7), i believe. correct me if that is wrong. Assume that UnCox = 60u UpCox = 30u lapta n = 0.1 lapta p = 0.2, how to calculate the output impedance?
The drain current in M9 is 3mA. M1 = 1.5mA M2 = 1.5mA.
ro = 1 / (lapta * Id)
I have calculated the otuput impedance of the op-amp which comes out to be 93k ohms. However, the book says it is 266k ohms. I used the equation,
Id = (UnCox/2) (W/L) (Vgs-Vt)^2
to figure out (Vgs-Vt)
Then I used (Vgs-Vt) to calculate gm. gm = (UnCox/2) (W/L) (Vgs-Vt)
I dont know where I made mistake. Checked my work twice. Please show me
a way to calculate the output impedance. thx