Imaging systems with column current mirror circuitry

摘要

Electronic devices may include image sensors having image pixel arrays with image pixels arranged in pixel rows and pixel columns. Each pixel column may be coupled to an active and an inactive current supply circuit. Each active current supply circuit may form a portion of a current mirror circuit that includes a common current source and a common input transistor. Each active current supply circuit may include a mirror transistor for mirroring current that flows through the common input transistor and a permanently enabled enabling transistor for activating that mirror transistor. Mirrored current that flows through a particular active mirror transistor may be supplied to image pixels in the pixel column associated with that particular mirror transistor. Each inactive current supply circuit may include a mirror transistor coupled to the input transistor and a permanently disabled enabling transistor.

主权项

1. An image sensor, comprising:
an array of image pixels arranged in pixel rows and pixel columns; a plurality of active current supply circuits; and a plurality of inactive current supply circuits, wherein at least one of the plurality of inactive current supply circuits and a corresponding one of the active current supply circuits are coupled to an associated one of the pixel columns, wherein the at least one of the plurality of inactive current supply circuits and the corresponding one of the active current supply circuits are coupled in parallel to the associated one of the pixel columns, wherein each image pixel in each pixel column comprises:
a photosensitive element; anda source follower transistor having a gate terminal coupled to the photosensitive element, wherein the source follower transistors of the image pixels in each pixel column are configured to receive a bias current from the active current supply circuit that is coupled to that pixel column, wherein, in combination with additional circuitry on the image sensor, each of the active current supply circuits forms a corresponding current mirror circuit for providing the bias current, and wherein the current mirror circuit corresponding to each of the active current supply circuits comprises a feedback-assisted current mirror circuit.