Design of a High-Speed and Low Power CMOS Comparator for A/D Converters

Comparators play a critical role in the analog to digital converters (ADCs) and digital to analog converters (DACs). So, different structures have been proposed to improve their performance. Power, delay, offset, and noise are the important factors that have significantly affect the comparator’s performance. In low power applications, power consumption and delay are the critical concerns that should be minimized to obtain better performance. In this work, a low-power and high-speed comparator has been proposed, which is suitable for applications operating at a low power supply.

Based on the conventional structure of the comparator, some modifications are implemented to achieve better performance in terms of power consumption and delay. Additionally, the proposed structure gives great performance when the difference of inputs is very small. To verify the proposed structure, it is designed and simulated in a 0.18 μm CMOS technology with a power supply of 1 V and sampling frequency of 2 MHz.

To draw a fair comparison, the conventional and proposed structure is simulated in equal circumstance. The size of transistors is designed with appropriate W/L ratios to achieve appropriate performance. The proposed structure not only reduces the power consumption by 44%, but also it decreases the delay by 9.1%. The power consumption of the proposed structure is around 0.12 µw. The total occupied area by the proposed structure is approximately 127.44 µm2.

In this paper, we presented a delay analysis for the proposed dynamic comparator. Also, based on theoretical analyses, a new dynamic comparator consumes less power and operates faster compared with the conventional structure. The simulation results verify the theoretical analysis.