GaN HEMT MMIC Doherty Power Amplifier With High Gain and High PAE

This paper presents an approach to maximize the gain and power-added efficiency (PAE) of a Doherty power amplifier (PA) using a 0.25 μm GaN pHEMT. The conventional carrier PA has an input matching for the ROPT load and does not deliver the 3 dB higher gain with 2ROPT load due to the mismatch and it degrades gain and PAE of the PA. To solve the problem, the input match of the carrier PA is optimized at the back-off power level with the 2ROPT output load, while the input is mismatched at a high power level. A Doherty PA with the concept is designed and implemented using a GaN pHEMT MMIC process at 1.8 GHz. The measured average output power, power-added efficiency and gain are 35.6 dBm, 56.3%, and 18.9 dB for a 10 MHz LTE signal with a 6.5 dB PAPR.