Source follower noise limitations in CMOS active pixel sensors

摘要

CMOS imagers are commonly employing pinned photodiode pixels and true correlated double sampling to eliminate kTC noise and achieve low noise performance. Low noise performance also depends on optimisation of the readout circuitry. This paper investigates the effect of the pixel source follower transistor on the overall noise performance through several characterization methods. The characterization methods are described, and experimental results are detailed. It is shown that the source follower noise can be the limiting factor of the image sensor and requires optimisation.