gEDA-user: possibly off topic -- minimum spice transistor size?

["Phillip Whitt" <phillip_whitt@gmx.co.uk>]

Hi all,

I started picking through various spice and design packages because of the
flaky nature of the windows apps i use in class.  I've been a Linux user for
about five years and up until recently have only played with the various *nix
based spice packages out of boredom.  Recently though, after picking up geda,
I have run into problems I cannot believe are what they appear.

When I set a W or L in a netlist to some value less than 1.2um, I receive an
error that the dimension is zero.  I cannot believe that the packages are so
outdated that they are unable to perform these simulations, are they?  1.2u
technology has been around for quite some time - certainly this isn't a
dead-end.  Orcad PSpice has so far dealt with every dimension I have thrown it
without failure.  I've had this problem using spice3f4, ngspice, tclspice and
several other small packages i had sitting around on disc.  It isn't something
stupid in the netlist either- i tried every notation i could think of, and
compared results from other dimentiosn to Pspice results- it's being
interpreted the same way in other environments, but works.  Unless of course one of you
happens to know of a dumb mistake that would act this way.  Hints?

This 1.2 limitation is killing me.  Next term I wanted to put some research
into short channel effects in transistors and will be comparing different
approximations and simulations...  It doesn't look good on the Linux front if
I'm limited to 1.2um- unless of course i start tweaking the model in completely
unrealistic fashion and have an xj of 1.5u...

Anyone know what the root of this problem is, or how i get around it?  The
model I'm using has Ld << 1.2u, and has simulated reliably in several windows
based apps.  A few other models I've tried, give the same error.

I really appreciate any feedback.  Thanks a lot.

Regards,
Phil


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