Large-signal and small-signal models for arbitrarily-doped four-terminal field-effect transistors

Models are derived for a four-terminal field-effect transistor (FTFET) with an arbitrary (one-dimensional) impurity distribution. The models apply for both four-terminal and conventional three-terminal devices operated in either the pinch-off or nonpinch-off modes; moreover, they describe behavior when either large or small signals are applied to the gates. The model parameters can be determined either from terminal measurements or from knowledge of the physical make-up. Because an arbitrary impurity distribution is assumed in their derivation, the models represent devices made with any of the common fabrication techniques. Measured step-function response of epitaxial, single-diffused and double-diffused FTFET´s shows good agreement with calculated behavior for broad ranges of resistive source and load terminations.