Analysis of class E amplifier with both linear and nonlinear shunt capacitance at any duty cycle, grading coefficient and supply modulation

Abstract

This work studies the effects of the drain pn capacitance grading coefficient, duty cycle and supply modulation on the operation of class E amplifier. The class E operation analysis with a combination of nonlinear and linear output capacitances is revisited and duty cycle is added to the equations to allow further investigations for optimum class E circuit tuning. The presented analysis method can be used for synthesis as well, where necessary load components are calculated for a transistor with a specific grading coefficient both in the output capacitance and in the nonlinear feedback capacitance. Further, the grading coefficient of the nonlinear output capacitance is varied in the paper while investigating the changes in normalized peak voltages and harmonics. Drain efficiency, supply-to-amplitude modulation (V dd /AM) and supply-to-phase modulation (V dd /PM) are studied. It is shown that by varying the device duty cycle, one can scale the optimum load and the level of peak voltages over the switching device. Also, the choice of grading coefficient affects the drain efficiency, V dd /AM and V dd /PM behaviour of the class E amplifier. Last, a case study about increasing the efficiency of a class E amplifier with hyperabrupt output junction capacitance is shown.