4T pixel structure based on semi-floating gate

Abstract

The invention discloses a 4T pixel structure based on a semi-floating gate. The 4T pixel structure comprises a semi-floating gate device MSFG, three switching tubes and a capacitor, wherein the semi-floating gate device is used for collecting signal charges; the capacitor is similar to a photoelectric conversion region in a traditional 4T pixel, can be a capacitor of any type, is determined according to specific design and is used for converting a current signal output by the semi-floating gate device into a voltage signal; the three switch tubes can be switch tubes of any type, are determinedaccording to specific design, and are respectively used as a source follower MSF, a reset tube MRST and a selection tube MSEL; the source follower is used for signal amplification, and the reset tubeis used for resetting signals in the capacitor; and the selection tube is used for controlling the output of a pixel array row signal through a time sequence; The structure solves a problem of voltage distribution in a traditional 4T pixel photoelectric detection region and a photoelectric conversion region, and compared with a 1T pixel structure based on a semi-floating gate device, the pixel design with high full well capacity, large output swing and low noise can be realized.

Description

technical field [0001] The invention relates to the field of CMOS image sensors, in particular to a 4T pixel design based on a half-floating gate capable of realizing high full well capacity, large output swing and low noise. Background technique [0002] Since the invention of passive pixel image sensors in the 1960s, CMOS image sensors have experienced the development of passive pixel image sensors, 3T active pixel image sensors, 4T active pixel image sensors, and digital pixel image sensors. [0003] The passive pixel structure includes a photodiode and a switch tube, and has the advantages of simple structure and high fill factor. The disadvantage is serious tailing and high noise. [0004] The 3T active pixel structure includes a photodiode and three switch tubes. The advantage is that the accumulated signal charge can be output without damage, and the signal-to-noise ratio is higher than that of passive pixels. The disadvantage is that the reset noise is large, and t...

AI Technical Summary

Problems solved by technology

[0008] Aiming at the technical problems existing in the prior art, the present invention proposes a 4T pixel structure based on a half-floating gate, which solves the voltage distribution problem seen in the photodetection area and photoelectric conversion area of ​​a traditional 4T pixel, and is relatively based on a half-floating gate device. For the 1T pixel structure, high full well capacity, large output swing, and low noise pixel design can be realized

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