A wideband voltage mode Doherty power amplifier

Abstract

This paper presents a new wideband Doherty Amplifier technique that can achieve high efficiency while maintaining excellent linearity. By modifying a “forgotten” topology originally proposed by Doherty, a new Doherty Amplifier architecture is realized with two voltage mode PAs and transformers, thus eliminating a narrowband impedance inverter. The voltage mode PA is implemented with a switched capacitor PA known for its excellent linearity. The PA is fabricated in 65 nm low-leakage CMOS and achieves 24 dBm saturated power (at standard supply voltage) with 45%/34% PAE at peak and 5.6dB back-off over 750 MHz to 1050 MHz 1dB bandwidth. With memory-less linearization, this PA can transmit 40 MHz 256-QAM 9dB PAPR 802.11ac modulation centered at 900 MHz meeting the spectral mask with measured EVM of -34.8dB and 22% PAE without backing-off or equalization.