Modeling for circuit and system design

The role of characterization and modeling is a vital one in bringing computers progressively into tighter loops in the design cycle. While a coordinated characterization effort provides the backbone of computation, it can also become an end in itself; it provides a bridge between several disciplines, particularly device development, circuit design, and computer analysis. Complete characterization includes several activities; selecting mathematical models for devices; developing measurement techniques, and measurement jigs; and devising statistical representations to account for manufacturing variability, environmental changes, and aging effects. Such a characterization effort with details of recent advances in bi-polar transistor modeling is outlined. In addition to tying together computer ac, dc, and transient analysis capability, the modeling approach allows investigation of "real world" effects such as manufacturing variability, temperature changes, and aging effects. This is an essential prerequisite for valid design studies.