A NEW CHARGE CONSERVING CAPACITANCE MODEL FOR GAAS-MESFETS

We present a new charge conserving capacitance model for Gallium-Arsen ide (GaAs) metal semiconductor field effect transistors (MESFET's) bas ed on the quasi-static approximation and a proper partitioning of the channel charge between the source and the drain terminals. A total of nine so-called transcapacitances were determined by taking derivatives of the various terminal charges with respect to the voltages at sourc e, drain, and gate. The transcapacitances are nonreciprocal, i.e., C-i j not equal C-ji when i not equal j, and can be organized in a 3 x 3 m atrix incorporating Kirchhoff's current law (charge conservation) and independence of reference. The present capacitance model is valid both above and below threshold, and shows good agreement with experimental data over a wide range of gate and drain biases. The model is analyti cal and suitable for implementation in circuit simulators.