Circuit for expanding pixel full well capacity of CMOS image sensor

Abstract

The invention relates to a circuit for expanding the pixel full well capacity of a CMOS (Complementary Metal-Oxide-Semiconductor Transistor) image sensor, which is technically characterized in that asource electrode of a second transistor is connected with a drain electrode of a third transistor, and a source electrode of the third transistor is connected to an analog column output bus; the gridelectrode of the second transistor, the source electrode of a fifth transistor and the negative electrode of a photodiode are jointly connected to one input end of the comparator; the output end of the comparator is connected with the drain electrode of the first transistor, the source electrode of the first transistor is connected with the first phase inverter, the output end of the first phase inverter is connected with the second phase inverter and one input end of the NAND gate, and the output end of the NAND gate is connected with the grid electrode of the fifth transistor; the output endof the second phase inverter is connected with a counter, the output end of the counter is connected to a three-state control switch, and the output end of the three-state control switch is connectedto a digital column output bus. According to the circuit, the super-large expansion function of the full-well capacity in a single pixel of the CMOS image sensor is realized by carrying out multipletimes of transfer counting reset on full-well charges.

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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