On analog comparators for CMOS digital pixel applications. A comparative study

Abstract

Abstract Voltage comparator is the only - apart from the light-to-voltage converter - analog component in the digital CMOS pixel. In this work, the influence of the analog comparator nonidealities on the performance of the digital pixel has been investigated. In particular, two versions of the digital pixel have been designed in 0.35 μm CMOS technology, each using a different type of analog comparator. The properties of both versions have been compared. The first pixel utilizes a differential comparator with the increased size and improved electrical performance. The second structure is based on a very simple non-differential comparator with a reduced size and degraded performance. Theoretical analysis of the comparator nonideality effect on the quality of the image obtained from the digital pixel matrix as well as simulation results are provided.