Using gschem to simulate active circuits with ngspice

I have gschem and ngspice running under Ubuntu Hardy and have successfully simulated passive (RLC) and a few with NPN and/or PNP transistors.

I am having difficulty properly setting up simulations using operational amplifiers (i.e. TL071) or MOSFETS (i.e. 2N7000). I have been able to successfully download the Spice 3 models (as 'subcircuits') from manufacturer's sites and associate them with the schematic symbols in gschem (by setting the 'file' attribute).

Possibly my problem is a misunderstanding of pin numbering and how to line up pin numbers on a schematic symbol with those in a subcircuit. I seem to have this problem with operational amplifiers especially.

There are also other strange things I am stuck on, for example, why the gschem MOSFET parts have varying numbers of pins:

nmos-1.sym: 4 pins nmos-2.sym: 4 pins nmos-3.sym: 3 pins

Which should be used for simulation with, for example, the 2N7000 model? I imagine it ia nmos-3.sym but what are the other symbols used for, in that case?

Can anyone recommend good books or other sources of information for guiding someone like me through the fundamentals of using Spice and gschem for active circuit simulation? I've seen many of the gEDA/ gschem tutorials and they all seem to skip this aspect to some extent. I could really get a lot from a single, clear article that explains how to set up a simple operational amplifier circuit simulation, step- by-step, in gEDA/gschem/ngspice!


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