A highly efficient WLAN CMOS PA with two-winding and single-winding combined transformer

In this paper, a fully integrated high-efficiency linear CMOS power amplifier (PA) is developed for 802.11g WLAN applications with the proposed power combining transformer. In comparison with conventional power combining transformers, the proposed power combining transformer can offer high-efficiency performances with a smaller die size. The fabricated two-stage PA using a 65nm CMOS technology achieves a saturated output power of 26.7 dBm with a drain efficiency (DE) of 47.7% at 2.48 GHz. The PA is tested with 54Mbps WLAN 802.11g signal and it meets the stringent error vector magnitude (EVM) and spectral mask requirements at a 20.13-dBm output power with a DE of 21.4%.