A 1.2-GHz comparator with adaptable offset in 0.35-μm CMOS

We apply the technique of floating-gate differential injection to a 1.2-GHz CMOS comparator to achieve arbitrary, accurate, and adaptable offsets. The comparator uses nonvolatile charge storage on floating-gate nodes for either offset nulling or automatic programming of a desired offset. We utilize impact-ionized pFET hot-electron injection to achieve fully automatic offset programming. The design has been fabricated in a commercially available 4-metal, 2-poly 0.35-mum CMOS process. Experimental results confirm the ability to reduce the variance of comparator offset by 3600times and to accurately program a desired offset with maximum observed residual offset of 469 muV and standard deviation of 199 mu V. We achieve controlled injection to accurately program the input offset to voltages uniformly distributed from -1 to 1 V. The comparator operates at 1.2 GHz with a power consumption of 3.3 mW.