Hi there,
I'm building a two-stage fully differential amp and I try to find the proper DC operating point, so I swept the width of the PMOS on the most top of first stage(i noted in the pic) and looked at the output node DC voltage of first stage.(I want to have around 800mV) First I did the sweep in 0.6u - 1.1u range, then I did it again in 0.7u - 1.1u range, the graphs are totally different! Even the width value appears in both graphs has different voltage results.
Did anyone deal with a similar problem before? I'm a newbie so the problem may be quite stupid, but any advice will help!
Thanks a lot!
Qihang
