A parasitic elimination bootstrapped switch and a fast settling residual amplifier for high-speed and high-resolution pipelined ADC

Abstract

This letter proposes a parasitic elimination bootstrapped switch and a fast settling residual amplifier to be used in multiplying digital-to-analog converter (MDAC) in order to improve the performance of pipelined ADC at high frequency. The parasitic elimination bootstrapped switch improves the sampling spurious free dynamic range (SFDR) by more than 6dB by shielding the nonlinear parasitic capacitance of the MOS transistor substrate. In addition, at high frequency, the negative zero point introduced by the later stage switch-capacitor circuit (which is easy to be ignored) will seriously deteriorates the settling time of residual amplifier in the former stage. A new zero-pole elimination technique is proposed, which greatly reduces the settling time of residual amplifier by nearly 11% and further improve the performance of MDAC. Simulated in 28nm CMOS technology, as the input signal is 1.38GHz, the former stage of the pipelined ADC implements high-speed high-resolution to obtain a SFDR of 75.77dB and a signal-to-noise-plus-distortion ratio (SNDR) of 68.05dB at a sampling frequency of 2.2GS/s.