THE LINEAR STATISTICAL DC MODEL OF GAAS-MESFET USING FACTOR-ANALYSIS

The linear statistical model of the GaAs MESFET's current generator is obtained by means of factor analysis. Three different MESFET determin istic models are taken into account in the analysis: the Statz model ( ST), the Materka-type model (MT) and a new proprietary model of MESFET with implanted channel (PLD). It is shown that statistical models obt ained using factor analysis provide excellent generation of the multid imensional random variable representing the drain current of MESFET. T he method of implementation of the statistical model into the SPICE pr ogram is presented. It is proved that for a strongly limited number of Monte Carlo analysis runs in that program, the statistical models con sidered in each case (ST, MT and PLD) enable good reconstruction of th e empirical factor structure. The empirical correlation matrix of mode l parameters is not reconstructed exactly by statistical modelling, bu t values of correlation matrix elements obtained From simulated data a re within the confidence intervals for the small sample. This paper pr oves that a formal approach to statistical modelling using factor anal ysis is the right path to follow, in spite of the fact, that CAD syste ms (PSpice[MicroSim Corp.], Microwave Harmonica[Compact Software]) are not designed properly for generation of the multidimensional random v ariable. It is obvious that further progress in implementation of stat istical methods in CAD software is required. Furthermore, a new approa ch to the MESFET's d.c. model is presented. The separate functions, de scribing the linear as well as the saturated region of MESFET output c haracteristics, are combined in the single equation. This way of model ling is particularly suitable for transistors with an implanted channe l.