A Self-Tuned Class-E Power Oscillator

Abstract

The efficiency and output power of a high- $Q$ Class-E power amplifier (PA) are very sensitive to the values of the circuit components. Any mismatch between the nominal Class-E frequency and the input clock frequency could result in considerable degradation in the efficiency and much change in the output power. In this paper, we present a new self-oscillating Class-E PA, or so-called Class-E power oscillator (PO), whose feedback network is mainly constructed of a low- $Q$ RC circuit. As a result, the phase response of the feedback network is almost flat around the operating frequency, and if the nominal Class-E frequency of the load network changes due to variations in the component values, the phase shift in the feedback network does not change considerably, and therefore, the Class-E operation of the circuit is substantially maintained. We also present a complete design procedure for the proposed Class-E PO. We have built and tested a sample Class-E PO based on the proposed circuit. At $V_{DD}= {\text{4.5}}\,{\text{V}}$ , the measured oscillation frequency, output power, and efficiency of the circuit are 800 kHz, 0.96 W, and 89%, respectively. Simulation and measurement results confirmed that the efficiency and output power of the proposed Class-E PO have small sensitivities to the variations in the component values; therefore, we call the proposed circuit a self-tuned Class-E PO.