Power-Efficiency Characteristics of Class-F and Inverse Class-F Synchronous Rectifiers

This paper presents analytic and experimental results for high-efficiency GaN HEMT class-F and inverse class-F (class-F-1) synchronous rectifiers. The rectifier designs are based on time-reversed duals of corresponding class-F amplifiers. A detailed analysis of the power efficiency of a class-F rectifier is presented. The analysis shows that, unlike the amplifier dual, the rectifier configuration does not have significant overlap loss because of device constraints in terms of operation in quadrant III. Consequently, the power efficiency of the class-F rectifier is slightly higher than the amplifier circuit under equal source power conditions. Experimental measurements are shown, which compare the rectification efficiency of a class-F rectifier with class-F-1 rectifiers. It is shown that operation of the rectifiers under back-off conditions mimics the power efficiency of an amplifier with envelope tracking. Based on this paper, it is concluded that the class-F-1 mode has better rectification efficiency compared with that of class-F, both at peak power and under back-off conditions.