Modeling of high-speed, large-signal transistor switching transients from s-parameter measurements

A new technique has been developed to derive the large-signal transient response of semiconductor devices from small-signal frequency response data. The large-signal switching response can be calculated for an arbitrary input signal voltage and risetime. This new technique utilizes the Fourier transformation to combine arrays of small-signal data to compute the response waveform. The input waveform is decomposed into a superposition of small pulses. The response to each pulse is obtained by Fourier transformation techniques, using s-parameter data at appropriate bias points. The sum of these responses approximates the overall transient response. Simulations were performed for a GaAs MESFET for step inputs with the risetimes of 8 nsec and 150 psec. Good agreement was obtained between simulated waveforms and measured output waveforms in risetime, magnitude and waveform shape. This algorithm is general and will work for other measured small-signal transfer parameters as a function of frequency and bias.