How to (and how not to) write a compact model in Verilog-A

Verilog-A was recently enhanced to provide greater support for compact modeling. In order for Verilog-A to become the standard language for compact model development and implementation, two more steps are necessary: compact model developers must become familiar with the language, and simulators must run compact models written in Verilog-A almost as quickly and reliably as those hand-coded in C. This paper addresses both of these steps: it provides a quick introduction to writing compact models in Verilog-A and, by indicating the sorts of techniques that compact model writers may use, helps simulator vendors understand the sorts of optimizations that are expected from their Vefilola-A interfaces.