A fully-integrated efficient CMOS inverse Class-D power amplifier for digital polar transmitters

We demonstrate a fully-integrated, high-efficiency inverse Class-D power amplifier in 65nm CMOS process. Such efficient switching amplifiers can form the core of digital polar transmitters. A comprehensive analytical framework has been developed to reveal the design trade-offs and enable efficiency maximization. Operating from a 1-V supply, the PA delivers 22dBm output power with a high efficiency of 44% without using any RF process options. The PA efficiency is comparable to that of state-of-the-art CMOS switching PAs, though it uses a much simpler output matching network. The PA has been integrated into a mixed-signal polar transmitter and meets the 802.11g (54Mbps 64QAM OFDM) spectral mask and EVM requirements with more than 18% average efficiency.