Dual-Adaptive Bias Scheme of Condition-Tolerant Doherty Power Amplifier for 5G Handsets

This study presents a dual-adaptive bias (DAB) scheme for controlling the bias of peak amplifiers (PeAs) in Doherty power amplifiers (DPAs). The proposed scheme enhances the robustness of DPAs under varying operating conditions, such as load variation, gain variation, and supply variation—common challenges associated with applying DPAs to handsets. The DAB incorporates a feedback loop to activate the PeAs and adapt to changing conditions. Additionally, it features a feedforward path that accelerates control and enables rapid response for handling wideband modulated signals specifically for 5G handsets that operate at 2.5 GHz. The fabricated DAB-DPA demonstrates improvements in robustness across various conditions, with its effectiveness confirmed experimentally. The combination of feedforward and feedback in the DAB enhances performance and robustness under nominal conditions. Experimental results confirm that the DPA can amplify 5G signals with a 100 MHz bandwidth without requiring digital predistortion (DPD), achieving 42.8% power-added efficiency (PAE) and −35 dBc adjacent channel leakage ratio (ACLR). The proposed technology has significant potential to improve handset battery life in the future.