Design Procedure for a High-Efficiency Class-E/F3 Power Amplifier

The switch voltage stress in a Class-E power amplifier (PA) is larger than that in any other switching PAs. A series resonant filter is added across the switch to filter out the third harmonic of the switch voltage and reduce the switch voltage stress. The new circuit is usually called a Class-E/F
₃
PA. The output power, the efficiency, and the component values of a Class-E/F
₃
PA can be sensitive to the design of the harmonic filter. In this article, we perform a sensitivity analysis on Class-E/F
₃
PA and provide guidelines to design a Class-E/F
₃
PA, which is robust against variations in the harmonic filter components. We also provide new design equations to calculate the component values. To validate the proposed design guidelines and equations, a prototype circuit was designed and implemented. At
${{\bm{V}}}_{\mathbf{DD}} = 4.5\;\mathbf{V}$
, the measured output power, the efficiency, and the switching frequency of the prototype PA were 0.96 W, 94.2%, and 800 kHz, respectively.