Design of the high speed, high accuracy and low power current comparators

Abstract

Comparators are non linear, decision making analog circuits, which find wide spread application in data converters, data transmission and others. Comparison can be done in terms of “Voltage” or “Current”. A current comparator can be referred as trans-impedance amplifiers which compares applied input currents and generate CMOS compatible output voltage. In this work, study and simulations of various current domain comparator circuits have been done; some of these follow basic analog circuit concepts like current mirroring and Voltage current feedback. This thesis presents a novel idea for analog current comparison with controlled hysteresis. Proposed circuit is based on current mirror and latching techniques. Comparator presented is designed optimally in 0.18μm CMOS process in LTspice environment. Designing issues have also been discussed for no hysteresis (or very less hysteresis) case, where comparator gives higher accuracy and speed at the cost of increased power consumption. In addition to this a simple circuit is proposed which satisfies high speed, high accuracy and low power consumption constraints for the mentioned technology parameters. It utilizes amplification properties of Common gate circuit for generating CMOS compatible output voltage by comparison of applied input signal current and reference current