Design of class-E power amplifier for zero-current switching operation with MOSFET nonlinear output parasitic capacitance

Abstract

The subnominal condition is defined as only the zero-current switching (ZCS) condition is satisfied. On the other hand, as the operating switching frequency increases, the effect of the MOSFET nonlinear output parasitic capacitance increases. This article introduced the design expressions with the analytical approaches for the design of the class-E power amplifier with a shunt inductor at the subnominal condition, taking into account the MOSFET nonlinear drain-to-source capacitance. The element's values for achieving the subnominal condition are expressed as a function of the phase shift between the input and output voltage. Moreover, the MOSFET nonlinear drain-to-source capacitance affects the switch-current waveform. Therefore, the switch-current waveform does not satisfy the class-E ZCS conditions if the nonlinear effect of the MOSFET output parasitic capacitance ignored. Using the class-E subnominal operation, the degree of the design freedom of the class-E power amplifier is increased by one. The maximum output power along with the increment of the operating frequency at the subnominal condition is obtained. A circuit design example using the proposed design procedure of the class-E power amplifier with ZCS condition is given. The waveforms obtained from the laboratory measurements showed the quantitative agreements with PSpice simulations that proved the usefulness and effectiveness of our proposed design expressions. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:801–808, 2014