A circuit for expanding the full well capacity of pixels in cmos image sensors

Abstract

The invention relates to a circuit for expanding the full well capacity of a pixel of a CMOS image sensor, and its technical characteristics are: the source of the second transistor is connected to the drain of the third transistor, and the source of the third transistor is connected to an analog column output bus; The gate of the second transistor, the source of the fifth transistor and the cathode of the photodiode are commonly connected to an input terminal of the comparator, the output terminal of the comparator is connected to the drain of the first transistor, and the source of the first transistor is connected to the first Inverter, the output terminal of the first inverter is connected with the second inverter and an input terminal of the NAND gate, and the output terminal of the NAND gate is connected with the gate of the fifth transistor; the second inverter The output end of the counter is connected to the counter, the output end of the counter is connected to the three-state control switch, and the output end of the three-state control switch is connected to the digital column output bus. The invention realizes the super large expansion function of the full well capacity in a single pixel of a CMOS image sensor by performing multiple transfer count resets on the full well charge.

Description

technical field [0001] The invention belongs to the technical field of semiconductor photodetection, in particular to a circuit for expanding the full well capacity of pixels of a CMOS image sensor. Background technique [0002] The current image sensor mainly has two kinds of CCD and CMOS. In the early days, due to the limitations of the technology level, CMOS image sensors had problems such as high noise and low sensitivity, while CCD image sensors, which were invented later than CMOS image sensors, began to develop rapidly and are widely used in military, aerospace, civil and industrial industries. field. However, with the advancement of CMOS technology, CMOS image sensors began to develop rapidly in the 1990s due to their advantages of low power consumption, low cost, high integration, and strong anti-radiation interference, and have basically reached the characteristics of CCD image sensors. Level. [0003] Different from the MOS capacitor structure of CCD, many of t...

AI Technical Summary

Problems solved by technology

However, the full well capacity obtained by the above method is still far from meeting the needs of some specific applications for ultra-large well capacity. For example, for CMOS image sensors used in all-day star-sensitive detection. Extremely strong, it is easy to cause the charge saturation of the image sensor, and the full well capacity needs to reach the Me level to realize daytime detection

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