This article introduces a single-supply balun-first three-way parallel Doherty power amplifier (PA) tailored for millimeter-wave (mm-wave) fifth-generation (5G) applications. It incorporates a bandwidth enhancement technique that widens the operational frequency range, enhances broadband power back-off (PBO) efficiency, and reduces impedance mismatch between differential PAs. Realized in 40-nm CMOS bulk technology with a core area of 0.77 mm2 , the prototype delivers a saturated power/peak gain surpassing 20 dBm/16 dB, and it demonstrates a drain efficiency (DE) exceeding 15%/22%/33% at 9.5 dB/6 dB/0 dB PBO across a 24–30 GHz band. The proposed mm-wave PA achieves EVM/ACLR values of − 24.3 dB/ − 30.1 dBc for a 1-GHz 64-QAM OFDM signal, operating at an average output power (Pout) of 9.4 dBm with an average DE of 15%. For a 50-MHz 1024-QAM OFDM signal, it achieves an average Pout/DE of 8.6 dBm/12% with EVM/ACLR of − 30 dB/ − 36.3 dBc.@en