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.