Large-signal model of picosecond FETs and measurement of the step response

An FET large-signal model is developed for the time-domain computer-aided design (CAD) of ultrafast circuits. Numerical 2-D look-up tables describe the nonlinear parameters; a DC and microwave FET characterization as a function of bias voltage, followed by parameter extraction, completely determines the tables of parameters. The model can be implemented with simulators handling 2-D tables and applied to commercial transistors without a detailed knowledge of the internal structure of the device. The step response of an NEC710 MESFET is measured and compared with the prediction of the model, demonstrating its accuracy in representing switching waveforms and transient phenomena in the range covering tens of picoseconds. The 20-ps switching time of the NEC710 shows that the modeling methodology, measurement, and simulation are adequate for studying picosecond transient phenomena in single transistors.< >