Re: gEDA-user: newbie opamp blues

[sdb@xxxxxxxxxx (Stuart Brorson)]

OK, you're using spice-sdb.  Great!!

Spice-sdb triggers off of the "pinseq" attribute to emit the pins in
the right order when netlisting.  You need to make sure that you
attach the pinseq attribute to the pins in order to have them
netlisted correctly in the output SPICE file.  Attaching attributes to
pins requires you to edit the symbol itself.

There may be an op-amp already set up in the SPICE symbol directory in
gschem.  You might try looking there.  I have forgotten if it is or
not. . . .

Also, when you try to create a SPICE model using an opamp, you need to
specify which .subckt or .model you want for the op-amp.  No SPICE
program has a generic "opamp" model built into it.  Therefore, you
need to get an opamp SPICE model file from somewhere (Google is your
friend), and then put the model file in your local directory.  Then
attach the "file" and "model-name" attributes to the opamp's
symbol. Read about how to use spice-sdb with gEDA here: 

http://www.brorson.com/gEDA/HOWTO/

I have some vendor SPICE models which you can play with linked here:

http://www.brorson.com/gEDA/SPICE/

They are not included in the gEDA distribution because they are not
GPLed.  

> In pspice, whatever it is is already done. I just poke in 
> the opamp, and everything comes out. In that software though, I have to 
> specify an actual opamp, such as a ua741, which I have been unable to 
> find in the geda parts list.

PSpice is commercial software which assumes you are an idiot and does
everything for you in its own rigid way.  GEDA is an open-source
project which requires you to learn a little more and do a little more
work than PSpice, but rewards you with more flexibility, power, and
control over your design.  GEDA also includes a community of smart
hackers who enjoy playing with electronics.  Welcome to the club!  

Happy SPICE hacking!

Stuart