Using SPICE Models

Perhaps the biggest benefit to using the SPICE-based Simulation Backends in QUCS-S is the ability to use industry-standard models for real devices. It’s very common for electronics manufacturers to provide free SPICE models for their devices, which you can utilize in simulating your designs.

Read on to learn how to bring these models into QUCS-S.

Warning

The examples in this section of the documentation have all been performed with the ngspice Simulation Backend.

Many of these concepts may also apply to the other SPICE-based backends (Xyce and SPICEOpus), however the syntax may be subtly different in some cases.

None of these examples will work in the QucsatorRF backend (it is not SPICE-compatible).

Modeling Methods

There are essentially two methods for modeling real devices in SPICE-based simulators:

  1. For discrete semiconductors and passives (FETs, BJTs, diodes, etc), you can use a Device Model.

    • This is most often done with the .MODEL directive, although sometimes .INCLUDE may be used as well.

  2. For complex devices (like integrated circuits), you can use a Subcircuit Model.

    • This is done with the SPICE .SUBCKT directive.

    • Note that this is NOT the same thing as a QUCS-S Subcircuit!

Additional Reading