Image sensor pixel unit and clamping circuit

Abstract

The invention relates to a pixel unit of an image sensor. The pixel unit comprises a transmitting gate, a source follower, a reset transistor and a photodetector, wherein the reset transistor is controlled by a word line switch, and the output of the reset transistor is connected to a floating diffusion (FD) region so as to control the source follower; and the photodetector is used for transmitting optical signals to a bit line through the transmitting gate and the source follower. In the embodiment, a first power supply generates a second power supply through a power switch, and the second power supply supplies power to the reset transistor and the source follower. In another embodiment, the first power supply supplies power to the source follower, the first power supply is adjusted by an adjuster to generate the second power supply, and the second power supply supplies power to the reset transistor through a second power switch.

Description

technical field [0001] The invention relates to a complementary metal oxide semiconductor (CMOS) image sensor, in particular to a CMOS image sensor capable of increasing the photosensitive area. Background technique [0002] A Complementary Metal Oxide Semiconductor (CMOS) image sensor is an electronic device used to capture images, which converts light intensity into electric charge, which is then converted into voltage and read out. figure 1 A pixel cell of a conventional four-transistor (4T) image sensor is shown, which includes a photodiode D and four transistors -M tx , M rst , M sf , M sel . When resetting the transistor M rst When the reset signal R is turned on, the voltage can be reset. Source follower M sf It can be used to buffer or amplify the integrated light signal of the photodiode D. When the transfer transistor M tx When the transmitted signal T is turned on, it can be used to transmit the accumulated light signal of the photodiode D. When selectin...

AI Technical Summary

Problems solved by technology

[0003] The traditional 4T pixel unit will occupy a considerable chip area, so it is not suitable for modern high-density CMOS image sensors

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