Re: Gnucap Newbie: did I come to the right place?

[al davis]

On Thu, 13 Feb 2020 15:35:13 +0100
Matthias Brennwald <address@hidden> wrote:
> Hello World! I am a Linux user who wants to simulate and optimise an audio
> amplifier before actually building it. When I was looking for a simulation
> tool I found Gnucap. However, I am not sure if Gnucap is right for me.
> Skimming through the manual, I realised that many things are not yet
> implemented.
> 
> For example, the input stage of my amplifier is a differential pair made
> from two 2SK170 JFet transistors. 


> According to the manual, JFet devices are
> not yet implemented in Gnucap. 

You may have an old version of gnucap.

JFet devices are available as plugins.  Several spice models of jfets
are in the "spice-models" plugin package.

tarball:
http://git.savannah.gnu.org/cgit/gnucap/gnucap-models.git/snapshot/gnucap-models-20171003.tar.gz

git repository:
http://git.savannah.gnu.org/cgit/gnucap/gnucap-models.git

From there, pick one.  If you don't have any other info, try
plugins/models-spice3f5/jfet .  Compile it, then in gnucap load it with
the command "load /path/to/jfet.so".  (substituting your real path).


> Also, even if JFets were implemented, I
> don't understand how I would tell Gnucap that my JFet is a 2SK170.

Gnucap does not maintain a database of specific models.  There are
millions of them, so there is no way we could keep track of it all.
So google it .. or use another search engine of your choice.  Look for
"2sk170 spice model".   This will lead you to a bunch of them.  

So you will need both the plugin, for the generic jfet model, and the
so-called "spice model", which is really parameters to be used with the
generic model for your specific device.  It's usually a one-liner, or a
few lines extended so it is equivalent to one line, beginning with the
keyword ".model".