An offset cancellation technique for comparators using body-voltage trimming

In this paper an offset cancellation technique based on body voltage trimming is presented to be used in the comparators employed in Flash or Successive-Approximation analog-to-digital converters. The proposed offset cancellation is achieved by body voltage adjustment using low-power simple analog control feedback circuit without any additional capacitive loading at the comparator output. The accuracy of the proposed technique is higher than its digital calibration counterparts due to its analog nature. The technique is employed in the design of a 6-bit 1-GSps Flash ADC in 0.18 μm CMOS technology. Simulation results show that using the proposed technique the standard deviation of the comparator offset is significantly reduced from 28 mV to 750 μV operating at 1-GHz with only 25 μW power in offset cancellation. The cancellation scheme generally improves the ENOB by approximately 0.5 bit after cancellation.