This paper presents an analytical design method for the high-efficiency Class-EF \(_{n}\) power amplifier (PA). The proposed Class-EF power amplifier overcomes the practical limitation of the large inductance required in the load network and has a low normalized switch voltage of 2. The description of the two new lumped element and transmission line load networks have been presented. It is essential to mention that the proposed load networks simultaneously satisfy the impedance requirements at fundamental, second, third, fourth, and fifth harmonics. However, dc-to-RF efficiency is theoretically higher than the Class-EF with a lower harmonic control circuit. More importantly, adding one or more higher-order harmonic components can further improve the voltage or current waveforms. When more harmonic tuning is applied, more ripples are generated. To verify the validity of the proposed PA, two design examples, one with lumped elements and the other with transmission lines, have been designed. The measured results show a wide bandwidth from 1.9 to 2.9 GHz. Over this frequency range, drain efficiency is between 70-83%, with output power greater than 39.5 dBm and power gain larger than 10 dB.
