A GaN HEMT Doherty amplifier with a series connected load

Abstract

Doherty introduced two types of concepts for high-efficiency amplifiers in 1936. One involved a shunt connected load and the other involved a series connected load. The first one is well known. We propose a microwave Doherty power amplifier with a series connected load using baluns. A 1.9 GHz GaN HEMT Doherty power amplifier was designed and fabricated. At 24 dBm middle and 31 dBm saturated output powers, the amplifier realized improved power efficiencies of 31% and 56%, respectively, compared to power efficiencies of 15% at 24 dBm output power and 57% at 34 dBm saturated power, respectively, obtained with a reference push-pull amplifier.