A 26-40 GHz GaN Doherty Power Amplifier with >20% PAE at 6-dB Back-Off Supporting Multi-Band 5G mm-Wave Applications

This paper presents a two-stage symmetrical wideband Doherty power amplifier (DPA) implemented on a 0.1μm gate-length GaN-on-SiC HEMT technology. The DPA features a low-pass π impedance inverting network (IIN), which effectively incorporates the equivalent output capacitance of the transistors in the final stage. Notably, the transistors in this stage are supplied by a single DC voltage delivered through a short-circuited stub within the post-matching network. As a result, the IIN is designed with minimal frequency-dependent components, enabling broadband operation at peak power and at 6 dB output power back-off (OPBO). On-wafer measurements under continuous-wave (CW) excitation demonstrate that the DPA delivers a saturated output power of 32.4−33.7dBm and a power-added efficiency (PAE) of 22.5−29% over 26 to 40 GHz. At 6 dB OPBO, the DPA achieves a PAE of 20−23% from 26 to 40 GHz, corresponding to a fractional bandwidth of 42.4%. To the author's best knowledge, this is the broadest circuit bandwidth reported to date for millimeter-wave DPAs.