On the Efficiency Enhancement of Voltage Mode Digital Doherty Power Amplifiers

This paper investigates the efficiency limits of an asymmetric Doherty power amplifier, made of two differently sized Switched-Capacitor Power Amplifiers (SCPAs). For each output power level, the optimal power partition between the two SCPAs that maximizes the efficiency is derived. The proposed analysis shows that the efficiency is strongly dependent on how the two SCPAs are controlled. Moreover, it is shown that optimal power partition leads to two Power Back-Off (PBO) efficiency peaks using just one supply voltage. All the theoretical results have been validated by simulations using a commercial 22 nm CMOS technology at an operation frequency of 2.4 GHz.