Scaleability of DC/AC non-linear dispersion models for microwave FETs

This paper addresses the issue of scaleability in circuit based models for FETs, emphasising for the first time the particularly difficult problems associated with the scaleability of DC/AC dispersion phenomena. Results of a study carried out on both MESFET and PHEMT foundry processes, show that while the differential DC/AC transconductance obeys straightforward scaling rules, the output conductance does not. An equivalent circuit based solution that incorporates a differential DC/AC dispersion modelling methodology is presented. The solution is compact, obeys the required conservation constraints and can account for the scaling inconsistencies observed in the output conductance.