A 1.2 V Single Supply Hybrid Current-/Voltage-Mode Three-Way Digital Doherty PA with Built-In Large-Signal Phase Compensation Achieving Less-Than 5° AM-PM

This paper presents a single supply (1.2V) hybrid current-/voltage-mode three-way digital Doherty PA with built-in large-signal phase compensation technique to improve the power amplifier (PA) efficiency at deep power back-off (PBO), substantially reduce AM-PM distortion, and further simply supply power management. The design leverages one current-mode digital PA (C-DPA) as the main path and two voltage-mode digital PAs (V-DPAs) as the two auxiliary paths, combined by three-way transformer-based series Doherty output network. As a proof-of-concept, the three-way hybrid digital Doherty PA is implemented in 45 nm CMOS SOI process occupying 3 mm-by-2 mm. It achieves +22.4 dBm peak output power (P_sat) together with 38.5/32.1/18.7% drain efficiency (DE) for the peak/3.4/9.3 dB output power back-off (PBO) at 2.3 GHz. The proposed digital Doherty PA demonstrates 1.26×/1.46× PBO efficiency enhancement, compared to an ideal class-B implementation at 3.4/9.3 dB PBO. The maximum AM-PM distortion is 4.7° at 2.3 GHz without using AM-PM look-up table (LUT). The measured error vector magnitude (EVM) of 64-QAM/40 MHz and 256QAM/10 MHz are -32 dB and -32.1 dB with 24.7% and 23.2% average DE without AM-PM LUT.