Power efficiency calculation of class E amplifier with nonlinear shunt capacitance

Power efficiency of a class E RF power amplifier versus dc supply voltage V_DD when the shunt capacitance of the class E amplifier is a nonlinear capacitance with the grading coefficient m = 0.5 is obtained. In the calculation of power efficiency, switching loss due to non-zero turning on of the MOSFET, power loss due to forward voltage drop of the MOSFET body diode, and power loss due to MOSFET on-resistance are incorporated. It is found that the highest power efficiency is obtained at a lower dc supply voltage than the designed dc supply voltage, even though the circuit was designed to achieve the nominal operation at the designed dc supply voltage. The calculation was performed with Mathcad programming and the results were verified with Pspice simulations.