Voltage Mode Doherty Power Amplifier

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 power amplifiers (PAs) and transformers, thus eliminating a narrowband impedance inverter. The voltage mode PA is implemented using switched capacitor PA techniques. The PA is fabricated in 65-nm low-leakage CMOS and achieves 24-dBm saturated power (at the standard supply voltage) with PAE of 45% at peak power and 34% at 5.6-dB back-off over 750 to 1050 MHz 1 dB bandwidth. With memory-less linearization, the PA can transmit 40 MHz 256-QAM 9 dB peak-to-average power ratio 802.11ac modulation centered at 900 MHz meeting the spectral mask with measured EVM of -34.8 dB and 22% PAE without backing off or equalization.