FIT-S, a simulation-based data-driven parameter extraction program

Abstract

FIT–S is an interactive program for extraction of device parameters for SPICE–like circuit simulators. It is based on a circuit simulator rather than an explicit set of model equations. Basic advantages of the proposed approach include: (1) explicit model equations need not be known as they are provided by the circuit simulation tool used, (2) fitting can be performed not only for single devices but for functional blocks or whole circuits as well, and (3) the same extractor can be used for a variety of devices and/or device models. The extractor supports numerical as well as symbolic simulation so repeated analyses of linearized circuit (for frequency domain analyses) can be performed very efficiently using the symbolic functions generated from the Coates flowgraph representation of the circuit. Several optimization methods are built into the program to provide robust as well as efficient fitting of device characteristics. Flexibility of the approach is obtained by specification of extraction details in the data sets rather than the extraction procedure. Parameter extraction for heterojunction bipolar transistors (HBT) is used as an illustration of FIT–S capabilities.