Anding Zhu

This article presents an analytical and design methodology for a fully integrated continuous-mode three-stage Doherty power amplifier (CMTS-DPA). The impedance solution space of three-stage DPAs has been expanded using the continuous-mode concept with analytical derivation. The corresponding impedance inverter network (IIN) parameters have also been analyzed, enabling broadband implementation of the proposed CMTS-DPA. To validate the proposed approach and architecture, a CMTS-DPA monolithic microwave integrated circuit (MMIC) operating from 5.8 to 8.2 GHz, designed and fabricated using a gallium nitride (GaN) high electron mobility transistor (HEMT) process, achieves a saturated power of around 10 W with a fractional bandwidth (FBW) of 34.3%. Furthermore, the fabricated CMTS-DPA maintains a drain efficiency (DE) of 38.1%–42.3% at the 9.5-dB back-off. When driven by 100/200-MHz 256-quadrature amplitude modulation (QAM) signals, it shows good adjacent channel power ratio (ACPR) and error vector magnitude (EVM) after digital predistortion (DPD).