Paired differential active pixel sensor

Abstract

An active pixel sensor includes a photosensitive device and a transistor that when paired with the transistor in an adjacent pixel will form a differential input pair of an operational amplifier, where the rest of the operational amplifier circuit is located off the active pixel sensor, and is shared by the rows or columns of the active pixel sensor array. A number of switches are included in the active pixel sensor to configure the inputs of the differential pair to couple with the photosensitive device or the feedback signal from the output of the operational amplifier such that the operational amplifier is configured for unit gain. The pair of differential transistors operate in current mode where the biasing can be included inside active pixel sensor (while the biasing transistor can be shared among the two pixels that form the differential pair) or off the active pixel sensors. It can also be configured to operate in voltage mode by using a different operational amplifier topology. There are a number switches that connect and isolate the active pixel sensors from the bit line which is shared by active pixel sensors in the active pixel sensor array. Those switches can also be configured in a way that a plurality of active pixel sensors are connected to the same bit line, such that they operate at the same time to enhance the sensitivity and dynamic range of the device. Photo-sensitive elements in close proximity can share the read out circuitry that includes the differential pair through a number of selection switches in order to increase the fill-rate of the active pixel sensors. A correlated double sampler can be connected to the output of the operational amplifier for providing a fixed pattern noise free signal.

Dependencies are inferred from the claim text.