This paper presents a 250MS/s pipelined ADC with 1.8Vpp full scale and low harmonic distortion implemented in 40nm CMOS. To reduce the large distortion of the conventional source follower when it drives a large sampling capacitor at a large swing
an improved current injection technique and a drain voltage bootstrapping technique were employed. Switches used for sampling and charge transfer in the ADC were implemented with thin-oxide devices to reduce the parasitic capacitance and charge injection. Moreover
on-chip LDOs were applied to provide safe supply voltages for these switches to protect thin-oxide devices from reliability problems. Test results show that with a 10.1MHz input
the ADC achieves the signal-to-noise and distortion (SNDR) of 68.3dB
the spurious free dynamic range (SFDR) of 76.4dBc and the total harmonic distortion (THD) of -75.1dBc at -1dBFS