A 0.18µm CMOS low-power charge-integration DPS for X-ray imaging

This paper presents a new CMOS active pixel sensor specifically for digital X-ray imagers. The proposed DPS architecture includes a novel lossless A/D conversion scheme, a dark current self-cancellation mechanism, as well as self-biasing and built-in test capabilities, all at pixel level. Furthermore, FPN compensation is achieved by introducing gain programmability inside the A/D converter of each individual pixel. The proposed CMOS circuits make extensive use of subthreshold transistor operation and circuit reuse to obtain a low-power and compact DPS cell. A circuit implementation in standard 0.18 μm CMOS 1-polySi 6-metal technology is presented together with experimental preliminary results.