Perspectives on Analytical Modeling of Small Geometry MOSFETs in SPICE for Low Voltage/Low Power CMOS Circuit Design

The present state of the art in analytical MOSFET modeling for SPICE circuit simulation is reviewed, with emphasis on the circuit design usage of these models. It is noted that the model formulation represents an upper limit of what is possible from any type of model, but that good parameter extraction is required to most closely approach that limit. The individual model types presently in common use are examined, with discussion of the behavior of each model, its strengths and weaknesses, its applicability to certain types of circuits, and criteria that a circuit design consumer can employ to judge a model before using it for circuit design. Some related issues, such as node charge and gate capacitance modeling, charge conservation, and statistical simulation of process variations, are also evaluated. Finally, new trends, directions, and requirements of MOSFET modeling for circuit simulation are considered.