A Current-Subtraction-Type Offset-Cancellation Technique for Comparator Circuit and its Application for Flash-Type ADC

Abstract

We proposed a comparator circuit scheme using a current-subtraction-type offset-cancellation technique. Chopper amps are commonly used in CMOS comparators. However, the drawback of chopper amp is reduction of offset cancellation effect by the coupling capacitor in the signal path. To overcome this problem, a new offset-cancellation technique is developed. The effect of the offset-cancellation technique is verified by a prototype ADC fabricated in a 0.18um CMOS.