Compact Triple-Transistor Doherty Amplifier Designs: Differential/Power Combining

This paper investigates two novel triple-transistor Doherty power amplifier (DPA) designs. A compact fully differential DPA topology will be firstly introduced. Three active devices, two carriers, and one peaking are combined in a very judicious way to amplify the differential signal like what a typical Doherty amplifier does. Due to the reduction of transistor number from four for a classic differential DPA to three, the realization cost and layout dimension is reduced simultaneously. A second triple-transistor design, which amplifies an in-phase input signal and outputs a combined single-ended one, is introduced next. Similar to the differential design, a twin-carrier single-peaking configuration is applied. The functions of Doherty amplification and power combining are well integrated. Theoretical analysis will be given for a deep understanding of the operation principles regarding these two proposed architectures. To validate their effectiveness, prototypes corresponding to them are implemented based on Cree´s GaN HEMT CGH40010. Experimental results demonstrate notably high drain efficiencies at saturation and 6-dB back-off regions for both of the designs.