JFET CIRCUIT SIMULATION USING SPICE IMPLEMENTED WITH AN IMPROVED MODEL

Junction field effect transistor (JFET) circuit simulation using an ex isting physics-based JFET model is presented. This improved model has more predictive capability than the conventional JFET model employed i n SPICE. Furthermore, it treats the linear and saturation regions in a unified mannner and includes the subthreshold behavior, an effect not accounted for in the conventional model. The improved model is implem ented into PSPICE run on a Sun workstation, and steady-state and trans ient responses are simulated for a JFET switching circuit and a JFET v oltage follower circuit. Results obtained from the improved model comp are favorably with that obtained from a two-dimensional device simulat or PISCES and from measurements. For JFET's operating outside the subt hreshold region, the conventional model with optimized parameters (ext racted from measurements) also shows good accuracy. However, large dis crepancies arise from the conventional model if JFET's are biased in t he subthreshold region or if default model parameters are used.