Spice is a powerful tool for circuit analysis. But it often surprises users with
. holes in its abilities and strange definitions
. lack of industry-wide standards
. the need for the user to model the physics of their circuit, not just draw the schematic

I hope this blog will educate users and promote discussion in these areas.

Creating your own Spice subcircuit

Creating a subcircuit allows you to reuse a portion of your circuit in other places in the same circuit. Or in another circuit. You can distribute the subcircuit to other Spice users (distributing any third party models/subcircuits called by your subcircuit may be restricted by copyright).

Manual Creation
The process of manually creating a subcircuit is tricky. See the link for an article I wrote some time ago on doing this.
CREATING A SPICE SUBCIRCUIT

Automating Subcircuit Creation
If you want to make a number of subcircuits, or a complex one, consider the Professional version of 5Spice Analysis (my program). It has a sophisticated tool to make the schematic circuit into a Spice subcircuit, along with guidance on doing this.

The schematic remains the master document and you can generate a revised version of the subcircuit at any time. Signal Sources and TestPoints can be used in the schematic to make testing easy but optionally be excluded from the subcircuit. Subcircuit parameters are supported.