Analytical method for determining equivalent circuit parameters of GaAs FETs

An analytical method has been developed that gives a simple and practical means of extracting small-signal equivalent circuit parameters (ECPs) of GaAs FETs with negligibly small bond-pad capacitances. Only the S-parameter measurement of the pinched-off cold field-effect transistor (FET) is enough to determine the extrinsic FET ECPs. The intrinsic FET ECPs of a medium-power Ku-band GaAs FET chip with a total gate width of 800 μm have been analytically extracted for two types of eight-element intrinsic FET models; Model 1 (Curtice model) and Model 2 that differ in the control voltage (V_G) definition. Model 2 with V_G defined across the gate-source capacitance is found more appropriate judging from the smaller frequency dependence of the ECPs and a better agreement between the calculated and measured S-parameters over 2-20 GHz