High Resolution CMOS Current Comparators

Abstract

A 2¿m CMOS current comparator prototype is presented with an input current comparison range of 140dB and virtual zero offset(≪10pA). The circuit uses capacitive sensing for high resolution and nonlinear feedback to achieve small input voltage variations in the complete input current range. Operation speed for low current is abot two orders of magnitude larger than for conventional circuits. Simplified modeling issues are used to compare alternative comparator architectures.