Re: gEDA-user: TwoStageAmp example

[al davis <ad136@xxxxxxxxxxxxxxxx>]

On Monday 02 April 2007 12:44, Patrick Doyle wrote:
> I'll take a look at that.  I read on Stuart's web page that
> ngspice "experienced a burst of development during 2004, and
> incorporates a number of new patches which have increased its
> stability and augmented its feature set, and is therefore the
> preferred open-source SPICE (for now)."  So I started by
> looking there.
>
> I was probably a little scared away from gnucap since it
> didn't have "spice" in its name :-)

Spectre  and Nanosim don't have spice in the name either, yet 
they are the preferred commercial simulators among those in the 
know.

Some people equate "spice" with circuit simulation.  To me that 
is equivalent to equating "FORTRAN" with mathematical 
programming, despite that fact that most of it is done in C++.

It's long past time to move away from Spice.  It has served us 
well, but we need more.  Gnucap is our project to make a more 
advanced simulator, closer to the commercial simulators like 
spectre and nanosim.

Spice has too much baggage for that.  It has pretty much 
remained stagnant since about 1990.  There have been minor 
enhancements and new models added, but the inside is the same.  
NG-spice has collected the impovements that were scattered and 
made some bug fixes, so  it is the preferred open-source SPICE.  
But, it's SPICE.

Gnucap was stalled around 2004, for reasons I cannot reveal now 
but will probably eventually leak out.  Development has been 
very active over the last year.  

The idea is not to duplicate spice.  Instead, learn from all of 
past work including spice, but not limited to it.  Back off, 
decide how to make something better and do it.  

It is more interactive, has better scripting, better probe 
capability.  The development version supports plugins, which 
dramatically adds to its capability in the long run.  One 
capability it has is to accept the models designed for other 
simulators, such as spice.  I'm referring to the "C" code here.  

The current snapshot has plugins with the complete set of BSIM 
models, from the oldest up to the new BSIM460 that hasn't made 
it to most commercial simulators yet.  There is also 
a "spice3f5" set, and a "ngspice17" set.  You attach the ones 
you want, and the rest don't get in the way.

I expect soon to be able to use other formats also as plugins.

The input language is changing to use Verilog-AMS by default, 
with Spice through a plugin.  I think (and so do several other 
experts) that the only thing holding back Verilog-AMS at 
replacing the Spice format is that no free simulators have it.

When I have to go back to Spice for something, it is always 
frustrating.  Spice probes are very limited.  There is no help 
when you run into problems.  The fourier analysis is not 
accurate enough to be useful.  

Gnucap has its drawbacks, but I am working on it.  The biggest 
one is the lack of beginner documentation.


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