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

[r <nbs.public@xxxxxxxxx>]

On Thu, Mar 5, 2009 at 2:23 AM, al davis <ad151@xxxxxxxxxxxxxxxx> wrote:
>
>> >
>> > 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.

Well, I'm not sure. I don't know how it is implemented in these
simulators. I guess these guys have simply modified the models (they
have modified quite a few other things there so I guess they wouldn't
have minded adding "m" parameter as well).

> 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.

Perhaps it could be done at the time of stamping the matrix - by
multiplying all gm's by a factor of "m". Then all the probes would
"just work". I have no idea how it could be done technically, though.

BTW, some simulators preprocess the netlist and reduce parallel
devices into a single device with an "m" parameter set. This gives a
huge performance boost in extracted sims.

-r.


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