Re: gEDA-user: Using .global statements in GNUcap and mult transistors

[al davis <ad151@xxxxxxxxxxxxxxxx>]

On Wednesday 04 March 2009, r wrote:
> On Wed, Mar 4, 2009 at 7:07 AM, al davis 
<ad151@xxxxxxxxxxxxxxxx> wrote:
> >> like it, for example, I put m=50 to report the full
> >> current instead of 1/50 of the current going into it.
> >
> > The Gnucap behavior is consistent with Hspice and Spectre.
> >  At least that is what I have been told.  I don't have
> > access to them to check it out.
>
> That's incorrect. Both Spectre and Hspice treat devices with
> m>1 as single entities.

ok ....  maybe you can help solve this.

I'm dealing with a policy that requires that unmodified models 
designed for other simulators, including unmodified spice 
models, can be used as plugins.

For example, the BSIM models from Berkeley.

It's my understanding that when you specify (for example) 
BSIM430, that means you want BSIM430, whatever that is, not 
BSIM440 or anything else.

Also, when a new one comes out, it should be able to be used as 
is, so you can have it right away.

Those models do not support the "m" parameter as supplied.

Now, also consider subcircuits ..  Specify "m=" when you 
instantiate a subckt ..  that propagates down to everything 
under it.  No exceptions.  If a device inside also 
specified "m", it's not an override, but a multiplier.

Also consider that there are a bunch of parameters that can be 
probed.  Some multiply, some divide, some are not changed.  
There is no indication in the code of which is which.  There 
could be hundreds of parameters that could be probed.  All that 
is known is a name and the type (real, int, string, ....) that 
it returns.  There is no notion of across, through, or anything 
that helps the decision of how to scale.

The only method I can think of is to add another section to 
the "wrapper.h" file, where you can arbitrarily define new 
probes (already on the to-do list), or a table where you can 
list the probes and mark how they are scaled.  Even that is not 
a full solution, because it only applies to models that use 
wrapper.h and spice-wrapper.cc.  Still, this is a manual 
operation, something that may not always be done.

If you have any better ideas, please tell me.




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