I'm trying to design a differential amplifier with current mirror biasing using the the gm/Id methodology. Hand calculations and the simulation results are not in agreement. (I've attached the relevant screenshots).
I'm new to the method and I'm trying to learn by designing an actual circuit.
I think one of the problems I'm having is with the calculated width W (from the gm/Id and Id/W relationship). The calculated W is 3.142e-5m and maximum W I've seen so far in the sm141064.ngspice file is 0.5um(I'm using the GF180mcu ngspice models).
Please I don't mind having a call for a tutorial on this design methodology. I'm an undergraduate I really need to learn these things. Thank you.