Image sensor with stacked pixels including charge sharing gates

Abstract

An image sensor includes a logic die, including column readout circuits and bitlines connected to the column readout circuits. A sensor die is overlaid on the logic die. The image sensor includes an array of detector elements, each including a sensing circuit on the sensor die, which includes a photodiode, a floating diffusion nodea charge sharing transistor coupled between the photodiode and the floating diffusion node, a reset transistor coupled to the floating diffusion node, and a source follower transistor. In each detector element, a pixel circuit on the logic die includes a select transistor, which has an input coupled to the output of the source follower and an output coupled to one of the bitlines. Two current memory circuits are coupled to the input of the select transistor and are configured to sense and output respective signals indicative of levels of noise in the detector element.