High speed, low offset voltage cmos comparator

Abstract

The Analog to digital converters are the key interface blocks between the continuous time domain and the discrete-time digital domain. The performance of high-speed data conversion and digital communication interfaces is generally limited by the speed and precision with which the function of comparison can be performed. Thus, comparator speed and precision play a vital role in high performance ADC’s. CMOS comparators suitable for integration in VLSI technologies have been successfully realized for audio frequency applications, such as analog - to-digital (A/D) converters. The speed and resolution of MOSFET comparators are typically limited by the inherent MOSFET characteristics of low trans-conductance and relatively large device mismatches. However, there are several techniques for dynamic offset cancellation, dynamic biasing, and analog pipelining which significantly improve the speed and resolution achievable in an MOS based comparator. The thesis proposes a novel approach which minimizes the offset of pre-amplifier as well as the latch with increment in the speed of the comparator. The total offset thus referred back to the input is minimized and hence the pre-amplifier gain be relaxed. The CMOS circuit is implemented in 0.18 μm technology and simulated in LT-Spice.