Improved Genetic Algorithm in SPICE OPUS for Model Parameter Extraction

SPICE is a widely used tool for simulation of analog circuits. Accurate models of devices are crucial for obtaining realistic results from the simulation. Although SPICE provides circuit designers with built-in models for most widely used devices many devices still must be modelled with subcircuit models in order to achieve sufficient accuracy. The hardest part of creating a SPICE model for a particular part is determining the parameter values of subcircuit elements. With analytical methods the problem quickly becomes impossible to manage. The only remaining alternative is optimisation. Use of SPICE OPUS optimisation capabilities for model parameter extraction is presented. Three commonly used optimisation methods are examined on examples and discussed in terms of their sensitivity to initial parameter values, speed and numeric stability.