Investigation of Inverse Class-E Power Amplifier at Sub-Nominal Condition for Any Duty Ratio

The performance of the inverse class-E power amplifier at sub-nominal condition for any duty ratio is investigated in this paper. Comparing with the inverse class-E power amplifier at nominal condition, which demands both zero-current-switching (ZCS) and zero-current-derivative-switching (ZCDS) conditions simultaneously, the presented inverse class-E power amplifier at sub-nominal condition is only restricted by the ZCS condition. The proposed power amplifier increases two design parameters because the ZCDS condition limitation is cancelled and the duty ratio can be arbitrarily set. The analytical results demonstrate that the theoretical drain efficiency is still 100% and that all the circuit elements can be adjusted by the two released parameters. Furthermore, the influences of the transistor´s parasitic switch-on resistor and output capacitor are investigated and a simulation example is given to verify the proposed design methodology´s accuracy. Although it is not sufficiently tolerant of the elements mismatches and the transistor´s parasitic capacitor in practical design, the inverse class-E power amplifier at sub-nominal condition is still one of the promising candidates for high-efficiency power amplifier design if the two drawbacks are appropriately averted.