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Godfrey Junior Member Offline Posts: 16	Reverse diode voltage Apr 21^st, 2008, 1:39pm Is there a parameter for modelling the junction to substrate diode? So if I take the drain of an nmos transistor below Vss, at some voltage the reverse diode of N diff to substrate should conduct. Same for a PMOS, if I take the drain above Vcc, at some voltage the P diff to N well diode must conduct.
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Geoffrey_Coram

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Massachusetts, USA

Re: Reverse diode voltage
Reply #1 - Apr 22^nd, 2008, 8:05am

Godfrey wrote on Apr 21^st, 2008, 1:39pm:

Is there a parameter for modelling the junction to substrate diode?

Generally, yes.

Are you using a BSIM3/4 or PSP model? Do you have a 4-terminal model? I've seen some 3-terminal discrete component models that don't have a substrate terminal. I've also seen some MOS models that don't include the diodes, because they expect you to put them in a subckt that contains the diode.

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Godfrey Junior Member Offline Posts: 16	Re: Reverse diode voltage Reply #2 - Apr 24^th, 2008, 2:02pm Its BSIM 3.3 with four terminal devices. The only parameter I can see which looks about the right value is Dvt1 which also sounds like it might be diode Vt?
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