Simple Design of a Class-J Amplifier With Predetermined Efficiency

We present theoretical background of a Class-J power amplifier (PA), with infinite number of harmonic components in the output voltage, explicitly deriving novel simple formulas which govern the amplifier efficiency. We also derive a novel design curve which governs the optimal PA parameters for a predetermined (high) efficiency. The presented theory is applied in a design and fabrication of a 1.5 GHz high-gain GaN HEMT PA. Measured drain efficiencies of the PA at 1 and 2 dB compression points are 55.2% and 70%, respectively. The maximum drain efficiency is higher than 85% at the saturated output power of 40 dBm. Measured (small signal) $S$- parameters, output power, gain, and drain efficiency of the PA compare extremely well with full-wave and circuit-based cosimulations.