Image sensor and high-conversion-gain and low-noise pixel readout circuit

Abstract

The invention provides a pixel circuit of a CMOS (complementary metal oxide semiconductor) image sensor, which is characterized by using at least two transferring transistors for respectively transferring the accumulated optical signals of corresponding photodetectors to a first node, using a resetting transistor for resetting the voltage of the first node as the preset resetting voltage of a second node, and using a source follower for buffering the integrated optical signals. In the embodiment of the invention, a capacitor is connected between the first node and the second node, so as to reduce the impact of the effective capacitance comprising the capacitance in the floating diffusion areas and the stray capacitance in the photodetectors and transferring transistors.

Description

Technical field [0001] The present invention relates to a complementary metal oxide semiconductor (CMOS) image sensor, in particular to a pixel readout circuit of a CMOS image sensor with a smaller area, and a pixel readout circuit with a feedback (or switching) capacitor Out of the circuit. Background technique [0002] A CMOS image sensor is an electronic device that captures images, for example, used in a camera to convert light intensity into electric charge, then convert it into voltage and read it out. Figure 1A A passive pixel sensor (PPS) is shown, which is a kind of traditional CMOS image sensor. For ease of description, only two pixels in the pixel array are shown in the figure. Each pixel contains a photodiode D and access transistor (or switch) M acc . Word line (e.g. WL 1 ) Are connected to pixels in the same row, and bit lines (such as BL) are connected to pixels in the same column. There is an amplifier 10 at the end of each bit line BL. [0003] Figure 1B The ...

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[0005] Figure 1C The pixel circuit will occupy a considerable chip a

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