Optimum and Suboptimum Operations of Class-E/F3 Power Amplifier with Nonlinear Shunt Capacitance at Different Grading Coefficient

This paper presents the theoretical analysis of the Class-E/F 3 power amplifier (PA) with nonlinear shunt capacitor at different grading coefficient ( m ), for both optimum (i.e., ZVS and ZVDS) and suboptimum (i.e., ZVS and non-ZVDS) operations. The effects that the grading coefficient has on the load network parameters, maximum operating frequency, and the peak switch voltage and current are investigated in details for m = 0 up to m = 0.8. Three design examples are given to explain the design procedure, and two circuit prototypes were built using power MOSFETs with m = 0.3 and m = 0.5 to validate the theory. The constructed PAs delivered an output power of 3.5 W/2.55 W and a drain efficiency of 92.3%/92% at an operating frequency of 3.8/3.85 MHz, respectively.