Generalization of conditions for 100% efficiency and nonzero output power in power amplifiers and frequency multipliers

In a previous paper, basic limitations on the switch current and voltage waveforms in single-ended switching-mode tuned power amplifiers have been discussed for perfect filtering of harmonics at the output. This paper expands on the previous idea by providing more general conditions for both nonzero output power and 100-percent efficiency at any number of harmonics in the output power. The load network and load are assumed to be passive and linear. It is shown that it is not possible to achieve both nonzero output power and 100-percent efficiency. In switching-mode circuits, it is not possible to eliminate both the transistor turnon switching loss and the transistor turnoff switching loss while obtaining nonzero output power; at least one of the switching losses must be nonzero at nonzero output power. The results presented here are useful in synthesis and analysis of high-efficiency power amplifiers and frequency multipliers.