Harmonic-tuned switching power amplifiers are attractive for many power applications from power converters to a wide range of RF circuits, due to their improved power efficiency over other amplifier classes. The most studied harmonic-tuned amplifier classes are the ZVS (zero-voltage switched) classes E and inverse-F along with their ZCS (zero-current switched) duals, classes F and inverse-E. These classes, however, are by no means the only possible tuning methods, and are not necessarily the most desirable. A more complete picture of the switching amplifier family can be seen in the figure. A new set of ZVS power amplifier classes, which includes both classes E and inverse-F as degenerate members, was discovered and named the E/F family. Among these, many show superior performance when compared to previously known classes. Also, by using a push-pull topology, many may be implemented with the circuit simplicity of a class-E amplifier. The basic topology of one of them, class E/Fodd is shown here. A new comprehensive analytic solution for switching amplifiers has also been developed, which gives new and interesting insights about their behavior while yielding exact solutions for all the members of the E/F family.

E/F ZVS Amplifier FamilyI
This device represents the first demonstrated switching amplifier in the new E/F2,odd class belonging to the new E/Fx family of switching power amplifiers. Besides demonstrating the feasibility of the E/Fodd push/pull amplifier family, this device exhibits 1.1kW, 85% drain efficiency and 17dB gain at 7MHz. The amplifier uses low cost switching MOSFETs and fits in a volume of only 900cm3, considerably smaller than is possible with a similar class-E design. The E/Fodd tuning technique first demonstrated with this device allows microwave switching amplifiers to be constructed in silicon, such as the 2.4GHz, 2.2W design recently reported by Caltech. Applications in the HF frequencies might include efficiency and/or operation frequency increases over traditional designs, as well as the size reductions shown in this device.

7-MHz, 1.1-kW Demonstration of the New E/F2,odd Switching Amplifier Class , Scott Kee, Ichiro Aoki and David Rutledge-submitted to the IEEE MTT-S Intl. Microwave Symposium, May 20-25, 2001, Phoenix, AZ.

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updated March 1, 2001