ANALYTICAL BIAS DEPENDENT NOISE MODEL FOR INP HEMTS

A practical device model for both high frequency small signal and nois e behavior of InP-HEMT's depending on both gate and drain voltage has been developed. The model is based on the two-piece linear approximati on using charge control and saturation velocity models, Combining larg e signal model and analytical expressions for the noise source paramet er P, R, and C, an analytical bias-dependent noise model can be obtain ed, For implementation into high frequency simulation software, the ex act calculated bias dependence was mathematically fitted by elementary functions, It could be shown that lowest noise is observed when the d rain current for maximum gain is reduced to a third while the drain vo ltage is reduced to the start of the saturation region V-ds = 0.6 V. M odeling scaling effects of the noise behavior shows that lowest noise is observed for a gate width of 1 x 40 mu m. Multi-finger layouts are preferable for gate widths above 70 mu m. Furthermore it is shown, tha t the optimum width of each finger decreases with the number of finger s.