US Patent 7602430 High-gain multicolor pixel sensor with reset noise cancellation

An active CMOS pixel sensor includes a red photodiode and a green photodiode coupled to sense nodes. Blue photodiodes are coupled to a blue sense node through select transistors. A blue reset transistor is coupled between a supply node and the blue sense node. A source-follower transistor is coupled to the blue sense node. A blue row-select transistor is coupled to the source-follower transistor and a biased blue column line. Red and green amplifier transistors have gates coupled to sense nodes, drains coupled to a supply node, and sources. Red and green reset transistors have drains coupled to the drains of the amplifier transistors, sources coupled to the sense nodes. Feedback capacitors couple the sense nodes to the reset transistor drains. Red and green row-select transistors have drains coupled to the sources of the amplifier transistors, sources coupled to biased column lines, and gates coupled to a red-green row-select line.