A Wide-Range 12b 150MS/s P-SAR ADC with Open-Loop Residue Amplifier for Ultrasound AFE

A wide-range wide-band ADC is a crucial part of the high-frequency ultrasound imaging system analog front-end (AFE). This paper presents a wide input range 12b 150MS/s pipelined-SAR ADC design using a novel linearized open-loop subthreshold residue amplifier. The nonlinearity of the traditional subthreshold differential input pair is examined. Based on the examination, a new open-loop amplifier with a combined fully- and pseudo-differential input pair is proposed and mathematically analyzed. The proposed 12b 150MS/s pipelined-SAR ADC with the new residue amplifier is implemented and simulated using 28nm CMOS technology, attaining 74dB SFDR, 63dB SNDR and 14fJ/conv-step with a 1.44V full-scale range.