Current-mediated, current-reset 768×512 active pixel sensor array

Abstract

A current-mode active pixel sensor (APS) architecture provides an alternative to voltage-mediated source-follower APS devices, offering an architecture that can be built in a digital CMOS technology with fewer FETs in the pixel and readout, fewer bus lines strapping the array and less clocking required for operation. A current-reset approach reduces fixed-pattern noise due to FET performance variations. The architecture is robust with respect to the process-induced variations in a digital process, though this comes at the expense ofincreased power consumption during current reset. A current-mode APS CMOS image sensor with a 768-by-512 array of 15/spl mu/m/sup 2/ pixels is presented in a photographic mode that demonstrates the device variable electronic shutter operation, the x-y addressable nature ofthe circuit, and the inherent antiblooming.