A MESFET variable-capacitance model for realizing MMIC voltage-controlled function

A variable-capacitance model for a GaAs MESFET three-terminal varactor applied to MMIC voltage-controlled runing frequency is presented. In this model, because the source is connected with the drain, the gate capacitance is only considered by analytical expressions, which are classified into three different regions for gate bias voltage: a before-pinch-off region, an after-pinch-off region, and a transition region. The model also includes the free-carrier movement in the active region, which is a very important contributor to the gate capacitance. The analytical results with the use of this model, compared with the experiment and other models, support the validity of the derived variable-capacitance model. © 1996 John Wiley & Sons, Inc.