CMOS implementation of a low power absolute value comparator circuit

Abstract

Absolute value comparators are becoming essential building blocks for new biomedical signal processing systems. Direct conversion of conventional comparators, which work on actual signal values, into absolute value comparators involve full wave rectifiers and this is suboptimal for a number of reasons. This paper presents a novel absolute value comparator circuit implemented without the use of full-wave rectifier blocks and with low complexity. The overall circuit consumes 113 nW from a 1V supply and is suitable for processing bio-signals in low power biomedical systems. The circuit has been fabricated in a 0.35 μm CMOS technology occupying an area of 0.07 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . A top-level implementation and analysis has also been presented. This would allow designers to perform comparisons between absolute values of input signals, by changing the circuit level implementations of each of the blocks to meet the system target specifications.