Direct extraction method of HEMT switch small‐signal model with multiparasitic capacitive current path

Abstract

It has been found that the analytical extraction methods cannot be applied to the usual test structure of the switch high electron-mobility transistor (HEMT) with a large-value gate grounded resistor. The significant effect of the precise multicapacitive current path on switch model precision has also been found. The multicapacitive current path here is different from the seemingly similar hypothesis proposed for the distributed parasitic effects at high frequencies (eg, D-band). In fact, for switch based HEMT, it is important to distinguish between the capacitive current paths accurately even at relatively low frequencies. Due to the existing of the large gate resistance, the usual capacitance mix decreases the accuracy of the switch model significantly. Thus an analytical method has been developed to calculate parasitic capacitances (the capacitance to ground and the interelectrode capacitance) through full-wave electromagnetic analysis. For practical applications and further verification, the whole HEMT switch small-signal models and the direct extraction methods are presented. The simulated results fit well with the measurements up to 40 GHz.