The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl Simulators >> Circuit Simulators >> Theoretical transconductance VS Cadence Spectre simulator transconductance https://designers-guide.org/forum/YaBB.pl?num=1500815549 Message started by niloun on Jul 23rd, 2017, 6:12am |
Title: Theoretical transconductance VS Cadence Spectre simulator transconductance Post by niloun on Jul 23rd, 2017, 6:12am I have calculated transconductance of a NMOS transistor with formula (2*Id/(Vgs-Vth)) and simulated the same circuit in Cadence Spectre with same parameters via two methods, including: 1) DC Analysis>Analog environment>Results>Print>DC operating points 2) plotting derivative of current in respect to Vgs, but Simulation results are different from theory (approximately two times) :o Would you please explain why does this happen? |
Title: Re: Theoretical transconductance VS Cadence Spectre simulator transconductance Post by Geoffrey_Coram on Jul 24th, 2017, 8:20am You might try larger devices - sometimes the analytic expressions are affected by short-channel or narrow-width effects. |
Title: Re: Theoretical transconductance VS Cadence Spectre simulator transconductance Post by DanielLam on Jul 24th, 2017, 9:35am I agree with Geoffrey. Try longer device lengths (and widths too while you're at it). At least 2-5um length should be good. Otherwise, if you want the equations to really match up well, you might try going to MOS lvl 3 models (have to make these yourself). |
Title: Re: Theoretical transconductance VS Cadence Spectre simulator transconductance Post by niloun on Jul 25th, 2017, 1:42am Geoffrey_Coram wrote on Jul 24th, 2017, 8:20am:
Thanks so much for the answer. |
Title: Re: Theoretical transconductance VS Cadence Spectre simulator transconductance Post by niloun on Jul 25th, 2017, 1:46am DanielLam wrote on Jul 24th, 2017, 9:35am:
Yes, Geoffrey is right , Longer device lengths solely solves the problem, The problem was short channel effect. |
The Designer's Guide Community Forum » Powered by YaBB 2.2.2! YaBB © 2000-2008. All Rights Reserved. |