Active Pixel Sensors: Concepts and Applications

This lecture discusses the concept of Active Pixel Sensors (APS) within the context of CMOS cameras. It begins with an overview of the APS architecture, highlighting the role of components such as the column and row address decoders, reset followers, and pixel configurations. The instructor explains the equivalent circuit of a pixel in an APS, detailing the function of the photodiode and various transistors involved in the reset and signal processing. The lecture further elaborates on the layout of a 3T APS, emphasizing the proximity of the photodiode to the source follower and its implications for fill factor and noise. The design of multiple pixels in an APS is also covered, showcasing how they interact within the system. The discussion includes advanced configurations like two-stage and three-stage source followers, illustrating their impact on charge-voltage conversion and overall performance. The lecture concludes with insights into the applications of APS technology in modern imaging systems.