Hello, I am currently studying for a digital circuit design course and had a question regarding circuit design here. The sample we were given was unfortunately incomplete and I am not told why this person was wrong here. I know the width sizing (assuming length is constant) of PMOS transistors in CMOS design is ~2.5x the width of NMOS in order to ensure similar current flow and more importantly propagation time, but I am a little confused on how those rules apply to series PMOS/NMOS and parallel PMOS/NMOS.
Am I right to assume that the width of Mpa should be such that the same current flows through that branch as in the parallel branch with Mpc, and thus would need to have double the width of Mpc, 20 microns? And that the width of Mpc is 10 microns because the two 5 micron width PMOS transistors Mpd and Mpe below add up to a 10 micron width transistor in the amount of current that passes through them?
Thank you for any help.