Re: gEDA-user: ngspice and parts

[sdb@xxxxxxxxxx (Stuart Brorson)]

> Is there a particular site, or a list of sites, available for 
> downloading spice parts? I found a bunch of diodes and a bunch of 
> transistors. But I still haven't found any that I'm actually *using*, 
> just some that are relatively comparable.

You usually can find SPICE .subckts on vendor websites.  Googling
around helps too. 

> Other than looking for spice files for parts that I really am using, I 
> am currently looking for an LM317, which wasn't included in the ngspice 
> install, even though a gschem symbol exists. Is that going to be true 
> for all gschem symbols? The symbol will exist, but I will have to hunt 
> down a spice file?

Here's a past posting about an LM317 model to sci.electronics.cad.
Caveat emptor.  

http://groups-beta.google.com/group/sci.electronics.cad/browse_frm/thread/fbf84f10d86a4d23/e66bf3354362d541?q=LM317+spice+model&rnum=3#e66bf3354362d541


> I presume that in many cases (if not in most cases), it's impractical to 
> write your own spice file due to the difficulty of measuring all of the 
> interesting values that go into it (especially in the case of diodes...I 
> expect other parts have similar difficulties.) The data sheets don't 
> even come close to containing all of the values that go into a spice 
> file (at least in the case of diodes.)

Generating a SPICE model or .subckt from the datasheet is difficult,
and best left to experts.  It requires understanding enough about the
guts of SPICE to be able to know what all the parameters mean.

> So finding spice files written by electronics manufacturers, or major 
> electronics companies is the way to go?

Yes.

Stuart