An Operational Amplifier Assisted Input Buffer and An Improved Bootstrapped Switch for High-Speed and High-Resolution ADCs

Abstract

Parasitic attenuation, memory effect and channel-length modulation limit the linearity of the state-of-the-art CMOS integrated ADC input buffer, this paper introduces an operational amplifier assisted input buffer that improves the linearity. A bootstrapped switch with improved linearity is also presented. Simulation results show that the proposed input buffer achieves an averaged SFDR improvement of 15dB in the first Nyquist zone. The proposed bootstrapped switch achieves 8.8dB SFDR improvement near Nyquist input frequency compared to the conventional circuit. The proposed techniques improved the linearity of the sampling front-end significantly.