Crippling SPICE Level 2 bug in VMAX param

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Article #735

#735

From: System Mangler
Date: Thu, 22 Jan 1987 09:00

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If VMAX is specified using the level 2 model, making the device very
short will make the current *small*, not huge.	An effective channel
length of zero, results in zero current; one would expect infinity.
This happens in every version of spice I can get my hands on.  Try it:

.model n nmos level=2 uo=500 tox=25nm Nsub=5e15 vto=0.8v vmax=50km/s
vdd	5 0 dc 5v
mlong	5 5 0 0 n W=1.0um L=0.8um
mshort	5 5 0 0 n W=1.0um L=0.2um
.op
.end

The workaround is to use level 3.

Don Speck   speck@vlsi.caltech.edu  {seismo,rutgers,ames}!cit-vax!speck

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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: arc1-ca.pugleaf.net!utzoo!mnetor!seismo!rutgers!ames!cit-vax!mangler
From: mangler@cit-vax.Caltech.Edu (System Mangler)
Newsgroups: comp.lsi
Subject: Crippling SPICE Level 2 bug in VMAX param
Message-ID: <1559@cit-vax.Caltech.Edu>
Date: Thu, 22-Jan-87 04:00:23 EST
Article-I.D.: cit-vax.1559
Posted: Thu Jan 22 04:00:23 1987
Date-Received: Thu, 22-Jan-87 18:56:07 EST
Organization: California Institute of Technology
Lines: 15
Keywords: velocity saturation