Gain partitioning: a new approach for analyzing the high-frequency performance of compound semiconductor FETs

A novel approach for analyzing the high-frequency performance of compound semiconductor FETs is presented. The approach is based on a circuit description that separates intrinsic and parasitic circuit elements of active devices in a general way. Mason's gain (U) and current gain (A_i) are used to illustrate this approach. Significant results from U are related to a more commonly used nomenclature involving maximum stable gain and maximum available gain and, in particular, to the transition from a potentially unstable device to a potentially stable device. Results show that the requirements for maximizing these cutoff frequencies are different. Minimized parasitic circuit elements maximize f_τ. A maximized f_max, on the contrary, may be obtained if interactions of parasitic and intrinsic circuit elements satisfy certain conditions