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Re: [Help-gnucap] level 3 model problem

From: al davis
Subject: Re: [Help-gnucap] level 3 model problem
Date: Mon, 5 Jul 2010 01:03:03 -0400
User-agent: KMail/1.13.3 (Linux/2.6.32-trunk-amd64; KDE/4.4.4; x86_64; ; )

On Wednesday 30 June 2010, Philipp Klaus Krause wrote:
> I'm rather new to gnucap, so this could be a user error, but:
> I've seen the following problem three times:
> gnucap just outputs lots of
> @@@unreachable:u_limit.h:110:fet_limit_vgs messages (and a
> R1.X1: RTEMP: effective length is negative or zero warning
> before). Each time it occoured using level 3 models (and I
> don't remember not seing the problem when using level 3
> models). I've tested on two different machines, both running
> Debian.

Obviously, it isn't unreachable.  It can get there if there is a 
numeric overflow.

You didn't say what version of gnucap.  There is a big 
difference between the stable branch (0.35) and the development 
branch (2009-12-07).

In the development branch, with plugins, there are 4 level 3 
mosfet models to choose from.  It might be interesting to see 
what the difference is.  Perhaps a convergence problem might be 
solved by using a different one.

I didn't run it, but I see a few issues ....

+ IS=7.4960E-9
+ N=2.0077
+ RS=.80464
*+ IKF=.1058
+ CJO=515.09E-15
+ M=.115
+ VJ=.6389
+ ISR=1.4182E-9
+ NR=4.9950
+ BV=90.375
+ IBV=10
+ TT=2.1640E-9

The * on the IKF line doesn't do what you think it does.  It 
makes the line a comment, and also disconnects lines that 
follow, so the CJO line is an extension to the comment, not to 
the model.  Gnucap does it like most programming languages do 
it.  I didn't realize how spice was different.

.print tran V(VccEN) V(pin) V(DC) V(logic) V(VppEN) i(VVpp) 
i(VVcc) V(inner)

Look at the extra probes that gnucap has.  A voltage source is 
not the best current probe.

.MODEL RTEMP RES (TC1=8E-3  TC2=5.5E-6)
R1  4 3     RTEMP 290E-3

When you use a the "RES" model for a resistor, the instance 
parameters are L and W, not resistance.  I thought this was 
"spice compatible" but perhaps it isn't compatible with some 
particular variant of spice.

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