A 348-μW 68.8-dB SNDR 20-MS/s Pipelined SAR ADC With a Closed-Loop Two-Stage Dynamic Amplifier

This letter presents a two-stage dynamic amplifier that achieves the high dc gain and PVT robustness of the residue amplifier in a pipelined successive approximation register (SAR) analog-to-digital converter (ADC). The proposed dynamic amplifier operates in a closed-loop configuration and does not require further calibration. The pipelined SAR ADC occupies 0.065 mm² in a 65-nm CMOS process. It achieves a peak signal-to-noise-and-distortion ratio (SNDR) of 68.8 dB at a sampling rate of 20 MS/s and draws 348 $\mu \text{W}$ from a 1.2-V supply. This corresponds to a Schreier FoM of 173.4 dB and a Walden FoM of 7.7 fJ/conv.-step. Furthermore, it maintains SNDRs over various sampling rates from 1 to 20 MS/s and its power consumption is scaled linearly.