Design technique for class E RF/MW amplifiers with linear equivalent of transistor’s output capacitance

Abstract

In class E amplifiers the nonlinear output capacitance of the device often reaches, or even exceeds the necessary value given by classical analysis in RF applications. The 100-percent efficiency condition imposes a constraint on the maximum susceptance value of the shunting capacitor consequently limiting the maximum frequency of the stage. In order to easily incorporate this nonlinear capacitance to the analysis and design of class E amplifiers, this paper addresses the use of a linear equivalent of a transistor nonlinear voltage-dependent output capacitance. The EQUIVALENT [Mediano, 2000] concept as well as a FORM FACTOR [Mediano, 2000] representing the quotient of the nonlinear capacitance to the linear theoretical case are used. Other important consequences affecting the normalization, design procedure and frequency scheme of class E amplifiers are also presented.