16.3 A 330mW 14b 6.8GS/s dual-mode RF DAC in 16nm FinFET achieving −70.8dBc ACPR in a 20MHz channel at 5.2GHz

Direct-RF synthesis has gained increasing attention in recent years [1] [2] as it simplifies the transmitter system by eliminating the intermediate frequency stage. It also offers the opportunity to address the extensive range of cellular bands with the same architecture and building blocks. Direct synthesis of carriers in the 5 to 6GHz unlicenced bands remains a challenge for RF-DACs operating in the 1st Nyquist band, as sampling rates in excess of 12GS/s are required. A more power efficient way to synthesize directly these frequencies is to use wideband mixing-DACs, which increase the output power in the 2nd and 3rd Nyquist bands [3]. In [3] the mixing is done using the quad-switch configuration, which doubles the number of switches and drivers, directly impacting the overall DAC width. In [4] the mixer is inserted in-line between the current cell switch and the output cascode, which requires additional headroom in the output stage. Both implementations impact the overall performance and power of the DAC even when the mixing operation is not used.