Pixel circuit, solid-state image pickup device, and camera system

Abstract

A pixel circuit has first, second, and third field effect transistors integrated and connected in series from a photoelectric conversion element to a side of an amplifier circuit. The first and second field effect transistors have gate electrodes to be simultaneously collectively driven. A threshold voltage of the first field effect transistor is set to be higher than that of the second field effect transistor. As the gate electrodes are driven step by step, electrons generated by the photoelectric conversion element and transferred via the first field effect transistor are accumulated in a channel region of the second field effect transistor. The electrons accumulated in the channel region are transferred to an input of the amplifier circuit via the third field effect transistor.

Description

technical field [0001] The present invention relates to a pixel circuit represented by a CMOS image sensor, a solid-state imaging device and a camera system. Background technique [0002] In recent years, CMOS imagers for digital cameras, camcorders, security cameras, etc. have been widely used and the market has expanded. [0003] A CMOS imager converts light incident on each pixel into electrons through a photodiode as a photoelectric conversion element, accumulates the electrons for a fixed period of time, digitizes a signal reflecting the amount of charge it has accumulated, and outputs the digitized signal to the outside. [0004] figure 1 is a schematic diagram showing an example of a pixel circuit including four transistors in one unit pixel. [0005] One unit of pixel circuit PX1 has photodiode 1 , transfer transistor 2 , reset transistor 3 , amplification circuit 4 , row selection transistor 5 , accumulation node 6 , and floating diffusion (FD, floating diffusion...

AI Technical Summary

Problems solved by technology

[0036] However, the dynamic range of the potential of the FD 7 is limited, so there are disadvantages in that the potential change amount ΔVf cannot be sufficiently increased and the S / N ratio cannot be increased

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