A Pseudodifferential Class AB DAC for Low-Power Wireless Transmitter

A low spurious 12-bit 122.88-MS/s digital-to-analog converter (DAC) enabling a low-power wireless transmit (Tx) chain is proposed and demonstrated. Pseudodifferential class AB DACs are introduced, and the benefits of using them in wireless Tx paths are discussed. The major power savings are achieved in multistage baseband Tx filters and upconversion mixers by using code-dependent linearly scaled dc that is generated from class AB transmit DACs. A two-channel I/Q DAC core consumes 6 mA with a 1.3/2.2-V dual supply. The 0.18-mm² I/Q DAC core fabricated in a 65-nm digital CMOS process, along with a highly integrated digital baseband processor and radio frequency transceiver, achieves a 73-dB spurious free dynamic range, 61-dB signal-to-noise-plus-distortion ratio, and -70-dB total harmonic distortion for a 990-kHz sinusoid at a 122.88-MS/s sample rate.