A Class-$E$ RF Power Amplifier With a Flat-Top Transistor-Voltage Waveform

Abstract

This paper shows a new class-$E$ amplifier topology with the objective to increase the nominal class-$E$ output power for a given voltage and current stress on the power transistor. To obtain that result, a parallel LC resonator is added to the load network, tuned to the second harmonic of the switching frequency. A class-$E$ power amplifier is obtained whose transistor-voltage waveform peak value is 81% of the peak value of the voltage of a nominal class- $E$ amplifier using the same dc supply voltage. In this amplifier, the peak voltage across the transistor is 3.0 times the dc supply voltage, instead of the 3.6 times associated with nominal class-$E$ amplifiers. A normalized design is presented, and the behavior of the circuit is analyzed with simulation showing that the ratio of output power versus transistor peak voltage times peak current is 20.4% better than the nominal class $E$. The proposed converter and normalized design approach are verified by simulations and measurements done on an experimental prototype.