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https://designers-guide.org/forum/YaBB.pl Simulators >> Circuit Simulators >> Question about the plot for gm/Id design methodology https://designers-guide.org/forum/YaBB.pl?num=1240299092 Message started by Yutao Liu on Apr 21st, 2009, 12:31am |
Title: Question about the plot for gm/Id design methodology Post by Yutao Liu on Apr 21st, 2009, 12:31am Hi everyone, I am confused about why the Vgs is set to be Vth+200mV when plotting gm*ro versus Vds. first, why the Vgs should be Vth+200mV while ploting gm*ro versus Vds? second, while sweeping Vds, the actual threshold voltage would change as well, how should I define the value of "Vth" in the "Vth+200mV"? And how should I implement this simulation in Spectre? |
Title: Re: Question about the plot for gm/Id design methodology Post by analogue_guy on Apr 22nd, 2009, 3:10pm Hi, I guess you want to bias your transistor in strong inversion, that is why you use Vth+200 mV. The standard textbook definition of strong inversion: VGS> Vthreshol + 6* Thermal voltage (kT/q). If you want some safety margin, you will end up at Vthreshold+200 mV. regards |
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