Abstract: An active pixel sensor implemented with CMOS technology that employs a plurality of photocells, each including a photodiode to sense illumination and a separate storage node with a stored charge that is discharged during an integration period by the photocurrent generated by the photodiode. Each photocell includes a switching network that couples the photocurrent to the storage node only during the integration period while ensuring that a relatively constant voltage is maintained across the photodiode during integration and non-integration periods. The transistors in the switching network operate in a forward active subthreshold region, ensuring linear operation and the diode voltage is clamped to a small positive voltage so that the diode is always reverse-biased. A source-follower generates a output signal correlated to the charge on the storage node that is coupled to column output circuitry that samples the signal.

Abstract: A color space converter is implemented using current mode analog circuitry to efficiently transform video data from a YC.sub.b C.sub.r format to an RGB format in order to allow the display of video signals on a color monitor. The analog current-mode circuitry is implemented in an integrated circuit that will operate at high clock rates and can be integrated in a small die area so as to reduce its cost. The color space converter includes Y, C.sub.b and C.sub.r current-mode conversion circuits to compute Y, C.sub.b and C.sub.r contributions to the G, R and B signals, and current-mode adders that add those contributions to the G, R and B signals to generate the G, R and B signals. Each conversion circuit includes (A) a respective folded cascode structure having an input coupled to a respective analog Y, C.sub.b or C.sub.r signal, each conversion circuit generating a respective Y, C.sub.b or C.sub.r current output; (B) at least one respective current mirror that generates from the Y, C.sub.b or C.sub.