Active Pixel Sensors: Design and Functionality

This lecture discusses the design and functionality of 7T active pixel sensors used in CMOS cameras. It begins by explaining the structure of the sensor, which includes a pinned photodiode, a reset transistor, and a floating diffusion. The instructor details the role of three transistors and CCDs that act as reservoirs, facilitating the transfer of signals. The layout of the sensor is described, highlighting the components such as the source follower and raw selector. The lecture emphasizes the advantages and disadvantages of the 7T design, particularly regarding the field factor. The process of correlated double sampling and global shutter operation is explained, detailing how the sensor captures images simultaneously across all pixels. The instructor outlines the steps involved in transferring data from the photodiode to the mid reservoir and then to the output diffusion, ensuring accurate signal reading. The lecture concludes with a mention of Sony's Pregius sensors, which utilize a similar three-reservoir system for enhanced performance.