A UNIVERSAL LARGE SMALL-SIGNAL 3-TERMINAL FET MODEL USING A NONQUASI-STATIC CHARGE-BASED APPROACH

We introduce a charge-based nonquasi-static large/small signal FET model that is extracted from measured small signal S-parameter and dc data, and can be applied to an arbitrary 3-terminal FET structure. The model is based on general physical principles, and provides consistent topologies for both large and small signal simulations to frequencies above f(t) and over a wide range of node voltages. The procedure for extracting model elements includes de-embedding linear parasitic elements and extracting bi-cubic, B-spline functions, which represent large signal model elements. The spline coefficients are calculated using a constrained least squares fit to a set of small signal parameters and/or dc currents that have been measured at a number of node voltage values. Advantages of this approach include fast parameter extraction for new FET structures, accuracy, computational efficiency, charge conservation, and the requirement of only a single model for all simulation modes. The model can also be used to interface device simulators (e.g., PISCES) with circuit simulators for accurate predictive modeling. Simulation results are demonstrated for a GaAs/AlGaAs MISFET.