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CMOS image sensor for reducing partition noise

An image sensor, pixel technology, applied in image communication, electric solid state devices, semiconductor devices, etc., can solve the problem of short turn-off time of transfer transistor TX

Inactive Publication Date: 2006-08-30
CROSSTEK CAPITAL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, due to the short off-time of the transfer transistor TX, not all channel electrons can move to the floating diffusion node FD

Method used

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  • CMOS image sensor for reducing partition noise
  • CMOS image sensor for reducing partition noise
  • CMOS image sensor for reducing partition noise

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0050] The first embodiment increases the falling time of the transfer control signal applied to the gate of the transfer transistor by reducing the W / L ratio of the NMOS transistor of the CMOS type driver DRV.

[0051] 7A to 7C are circuit diagrams describing a driver for controlling a transfer transistor according to a first embodiment of the present invention.

[0052] The CMOS inverter type driver shown in FIG. 7A includes a PMOS transistor P and an NMOS transistor N connected in series between a power supply voltage VDD and a ground voltage VSS. The CMOS inverter type driver receives an input signal IN through the gates of these two transistors to show an inverted signal OUT.

[0053] Assuming that the W / L ratio of the NMOS transistor N is K, by increasing the length L or decreasing the width W, the resistance can be increased, that is, the current can be reduced, thereby increasing the fall time of the transfer control signal.

[0054] Meanwhile, the width W of the gate...

Embodiment 2

[0063] The second embodiment increases the fall time (τ) of the transfer transistor by adding a capacitor C. FIG.

[0064] Figure 9 and 10 is a diagram describing a CMOS type driver for driving a transfer transistor according to a second embodiment of the present invention.

[0065] As shown, the CMOS image sensor includes a plurality of unit pixels P1 to P1280 and a CMOS type driver DRV. Each unit pixel P1 to P1280 includes a photodiode, a floating diffusion node, a transfer transistor, a reset transistor, a driving transistor, and a selection transistor. The CMOS type driver DRV controls the turn-on and turn-off operations of the transfer transistors TX1 to TX1280 included in the unit pixel.

[0066] As an example of the CMOS type driver DRV, a CMOS inverter type driver is shown. A plurality of unit pixels P1 to P1280 are arranged in a single row. Accordingly, the CMOS type driver DRV simultaneously controls a plurality of transfer transistors TX1 to TX1280 of unit pix...

Embodiment 3

[0074] By partially modifying the structure of the first embodiment, the layout can be designed more simply.

[0075] Figures 11A to 11C is a circuit diagram of a driver for controlling a transfer transistor according to a third embodiment of the present invention.

[0076] As shown, the CMOS inverter type driver includes one PMOS transistor P111 and four NMOS transistors N111 to N114 connected in series.

[0077] Although the basic structure is similar to that of FIG. 7C, the sources of the NMOS transistors N111 to N114 are commonly connected to the ground voltage VSS, thereby forming a kind of resistor.

[0078] exist Figure 11A , the sources of the NMOS transistors N111 to N114 are commonly connected to the ground voltage VSS. exist Figure 11B , the sources of the NMOS transistors N112 to N114 are commonly connected to the ground voltage VSS. exist Figure 11C In , the source of no NMOS transistor is connected to the ground voltage VSS.

[0079] exist Figures 11...

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Abstract

A CMOS image sensor according to an embodiment of the present invention includes a unit pixel, including a transfer transistor controlled by a transfer control signal; and a transfer control signal controller for controlling a rising and a falling times of the transfer control signal, wherein the falling time of the transfer control signal is sufficiently increased to reduce a partition noise.

Description

technical field [0001] The present invention relates to a CMOS image sensor; and more particularly, to a CMOS image sensor that reduces allocation noise by prolonging the falling time of a transfer control signal applied to a gate of a transfer transistor. Background technique [0002] Image sensors are semiconductor devices that convert light images into electrical signals. Image sensors are classified into Charge Coupled Device (hereinafter, referred to as CCD) image sensors and Complementary Metal Oxide Semiconductor (hereinafter, referred to as CMOS) image sensors. [0003] A CCD image sensor includes at least one capacitor. These capacitors are arranged in close proximity to each other, and charge carriers are stored in and transferred to the capacitors. [0004] In contrast, a CMOS image sensor includes a plurality of unit pixels manufactured through a CMOS process. Each of the unit pixels includes a photodiode and three or four MOS transistors for driving the unit ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04N5/335H01L27/146H04N25/00
CPCH01L27/14601H04N5/3651H04N25/671H01L27/146
Inventor 裴昌民沈敬珍
Owner CROSSTEK CAPITAL
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