A GaAs MESFET small-signal equivalent circuit including transmission line effects

A small-signal equivalent circuit for the GaAs MESFET, suitable for the design of integrated circuits, was developed that includes the following features: (1) at high frequencies, the gate channel has the character of an RC transmission line, for which a pi -equivalent representation is used; (2) under saturated current conditions, a stationary high-field domain may be present in the conducting channel, for which an equivalent is derived in terms of a small-signal admittance. The resulting equivalent circuit was optimized with very good results by modeling process average S-parameters between 1 and 25 GHz for a 1 mu m gate device. The basic structure of the model is relevant for other FET designs such as heterostructure FETs (HEMTs) and devices with submicrometer gate lengths.<
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