Improved passive model for transient prediction of GaAs E/D MESFET analogue switches

An improved passive model of a GaAs MESFET is presented, where the intrinsic elements have a continuous dependence on gate, source and drain voltages for the benefit of transient prediction. Based on this passive model and circuit equations, the transient behaviour of analogue switches with GaAs E/D MESFETs is characterised with transfer time and transient error voltage in the time domain. An analytical expression is derived for the transfer time calculation of symmetrical devices that explains the influence of parasitic and external resistances. The transient error voltage induced by clock feedthrough is calculated in the E/D MESFET switches with a general load. Load and parasitic capacitances reduce the voltage amplitude of transient errors induced by a transient breakthrough in the switches with a low impedance load, but they increase its transfer time. Good agreement is obtained between theoretical prediction and measurement on the transient breakthrough with 0.5 μm GaAs E/D MESFETs