Novel non-linear equivalent circuit extraction scheme for microwave field-effect transistors

Non-linear equivalent circuits of microwave field-effect transistors (MESFET's, HEMT's) are now recognised to be of prime importance for the accurate design of microwave circuits, especially in monolithic technology. Many topologies have been proposed so far, together with extraction techniques [1-8]; recently, also some fundamental problems of physical consistency have been recognised and addressed [9, 10]. In the present work we propose an extended topology of the equivalent circuit that correctly represents the physical structure of the transistor and allows the fulfilment of the mentioned consistency constraints. For this circuit a practical extraction method is proposed, for the accurate and non-destructive evaluation of parasitic and intrinsic elements of the equivalent circuit. In addition, an altemative extraction method is introduced, that allows the simultaneous identification of both the bias dependent intrinsic elements and the reactive parasitic elements, at standard full-bias operating conditions.