A Multimode GaN Doherty Power Amplifier MMIC With N-Scalable Amplifiers for Selective Back-Off Power Level

This article presents a multimode Doherty power amplifier (M-DPA) monolithic microwave integrated circuit (MMIC). The M-DPA comprises of a load network (LN) based on a combination of current- and voltage-combining methods. By arranging the turn-on transitions of four parallel amplifiers based on the input power level, two carrier and two peaking amplifiers (2C2P) mode for 6-dB output power back-off (OBO) or one carrier and three peaking amplifiers (1C3P) mode for 12-dB OBO can be configured. The performances between efficiency and gain can be balanced according to the selected mode. The M-DPA concept was theoretically expanded to a generalized structure based on N (or = 2^m) scalable amplifiers in parallel that were simply modeled as current sources. This generalized M-DPA supports N-1 different operation modes with m different OBO levels. For verification, the M-DPA MMIC was implemented using a 0. 25- m gallium nitride (GAN) -HEMT process for 5G new radio (NR) applications (3. 3–3. 6-GHz band). Using a 5G NR downlink signal with a signal bandwidth of 100 MHz and a peak-to-average power ratio (PAPR) of 7. 86 dB, at a frequency of 3. 55 GHz, the drain efficiencies (DEs) of 37. 7 and 33. 8% and power gains of 8. 3 and 6. 4 dB were obtained for the 2C2P mode with an average output power of 37. 0 dBm and for the 1C3P mode with an average output power of 31. 0 dBm, respectively.