A low propagation delay dispersion comparator for low cost level-crossing ADCs

Abstract

This paper presents a low delay dispersion comparator for low cost level-crossing Analog-to-Digital converters. The conventional comparator circuit is modified by adding a variable driving-current block (VDCB) which is used such that it supplies the output node of the differential amplifier with a current that is inversely proportional with the level of input signal. The modification incurs small area overhead (only three transistors) compared with the previous works. The proposed comparator is designed in order to reduce the propagation delay dispersion caused by variable input overdrive and the common mode level. The proposed circuit is implemented in 130nm technology. The simulation results show that the overdrive-related propagation delay dispersion of the proposed technique is 27% of its counterpart in the conventional comparator for an input frequency up to 600MHz. The active area of the technique140.2 μm2 and the power consumption is 250 μW at 200MHz.