Over 10MHz bandwidth envelope-tracking DC/DC converter for flexible high power GaN amplifiers

This paper describes a fast envelope-tracking circuit capable of 10 MHz (up to 17.5 MHz) bandwidth based on RF GaN switching devices and 50 MHz switching frequency. The efficiency of the VHF converter is 84% to 90% which is comparable to a conventional DC/DC converter for spaceborne application. A demonstrator has been built and mated with a RF GaN HEMT output stage. The C/I measurement for 10-12W RF output power close to saturation show a linearity improvement by 5-8 dB and an efficiency improvement of up to 8 points when compared to the case of no tracking circuit.