A Differential Digital 4-Way Doherty Power Amplifier with 48% Peak Drain Efficiency for Low Power Applications

Abstract

This paper presents a differential digital 4-way Doherty power amplifier (PA) for low-power applications that achieves high efficiency in deep power back-off (PBO) without supply switching. The PA uses compact input and output matching networks through consolidation of various elements. A proof-of-concept PA was implemented in a 65 nm general purpose CMOS process, and it achieves a peak output stage drain efficiency (DE) of 48% at 4.75 GHz with 7.3 dBm output power (P out ). Also, it achieves peak PBO enhancements at 5.25 GHz with a DE of 42% at 0 dB PBO and 20% at 12.8 dB PBO. This corresponds to 2.2× improvement compared to normalized class B PA. The PA achieves an error vector magnitude (EVM) of −20 dB for a 1 Msym/s 16 QAM baseband signal with an average P out of 2.9 dBm and DE of 34% at 5.25 GHz.