Gnucap has three distinct styles of adding models:
-
Model Compiler
- is the easiest way to add models, but the least
flexible. The model compiler generates .cc and .h files using the
enhanced subcircuit mode. It is possible to develop models
with almost no knowledge of the simulator internals. In most cases,
this is the preferred way. The standard MOSFET and diode models are
done this way.
- Enhanced subcircuit
- is less efficient than primitive but
has other advantages that make it preferable to primitive when
you can use it. The model is defined as a combination of equations
and topology. The AC and pole-zero code is inherited from a base
class, so you don't need to to it. You need to understand the
simulator's internals, and it is not likely to be portable to other
simulators.
- Primitive
- should be used only when absolutely necessary. If it
is done correctly, it will result in the fastest execution, but you
need to do everything. It requires thorough knowledge of the
simulator internals, including how Gnucap is different from other
simulators. If you miss some of the details, it is possible that
your model will work but slow down the simulator significantly.
Most of the primitive devices (resistors, sources) are done this
way. A few device types that have special considerations, like
gates and transmission lines, are also done this way.