An Ultrawideband Distributed-Doherty Amplifier With Frequency-Shaping Adaptive Bias

This letter presents the design and implementation of a distributed Doherty power amplifier (DDPA) employing a multibias matching network (MBMN) and frequency-shaping adaptive bias (FSAB) techniques. MBMN effectively compensates for phase variation characteristics with lower dc bias loss, thereby significantly enhancing the DDPA’s bandwidth and efficiency. To address the limitation of insufficient high-frequency bias voltage, FSAB dynamically adjusts the gate bias according to frequency. Implemented in a 0.25-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula>m gallium nitride (GaN) process, the prototype amplifier achieves 1.5–6.8-GHz bandwidth. Experimental characterization demonstrates drain efficiency (DE) of 38–47% across the full band while occupying a compact <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.3\times 4$</tex-math> </inline-formula> mm die area.