Small-signal, high-frequency equivalent circuit for the metal¿oxide¿semiconductor field-effect transistor

The differential equations describing the small-signal sinusoidal operation of the `intrinsic¿ m.o.s.f.e.t. structure are solved using modified Bessel functions of the first kind. Expressions for the small-signal short-circuit admittance parameters are obtained in series form. By retaining appropriate terms in the series, the elements of a convenient equivalent circuit are computed for both the nonpinchoff and the pinchoff cases. Results are compared with those presented by other authors, to show that previous calculations for the nonpinchoff case are incorrect.