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

Abstract

This paper presents an approach to maximize the gain and power-added efficiency (PAE) of a Doherty power amplifier (PA) using a 0.25 $\mu$ m GaN pHEMT. The conventional carrier PA has an input matching for the ${R}_{\rm OPT}$ load and does not deliver the 3 dB higher gain with ${2R}_{\rm OPT}$ 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 ${2R}_{\rm OPT}$ 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.