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CMOS (Complementary Metal Oxide Semiconductor) image sensor

An image sensor and pixel unit technology, applied in the field of image sensors, can solve the problems of limited bandwidth of negative feedback operational amplifier A and limited effect of eliminating reset noise, etc., and achieve the effect of ensuring removal of reset noise, reduction of reset noise, and stable voltage

Active Publication Date: 2010-08-25
BRIGATES MICROELECTRONICS KUNSHAN
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] However, it is found in practice that the disadvantage of the above-mentioned CMOS image sensor is that the negative feedback operational amplifier A can only eliminate the noise part whose bandwidth is within the bandwidth of the negative feedback operational amplifier A, but in practice, the negative feedback operational amplifier A has a limited bandwidth and eliminates reset noise limited effect

Method used

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Examples

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no. 1 example

[0042] Please refer to FIG. 3 , which is a schematic circuit diagram of a 3T CMOS image sensor according to a first embodiment of the present invention. The CMOS image sensor includes a pixel unit 201 , a feedback unit 203 and a reset unit 202 . The 3T type CMOS image sensor in the present invention specifically means that the pixel unit 201 includes one photodiode and three NMOS transistors, namely: photodiode PD, reset transistor M1, amplifier transistor M2, and selection transistor M3. The reset transistor M1 has a source, and the source is called the sensing node FD of the pixel unit by those skilled in the art.

[0043] Continuing to refer to FIG. 3 , the feedback unit 203 includes a negative feedback operational amplifier A, and the negative feedback operational amplifier A includes an input negative terminal V - , input positive terminal V + and the output V out , the input negative terminal V - electrically connected to the source of select transistor M3, the input...

no. 2 example

[0073] FIG. 5 is a schematic diagram of a circuit structure of a 4T CMOS image sensor according to a second embodiment of the present invention.

[0074] The CMOS image sensor includes a pixel unit 201 , a feedback unit 203 and a reset unit 202 . The 4T type CMOS image sensor described in the present invention specifically means that the pixel unit 201 includes 1 photodiode and 4 NMOS transistors, which are respectively: photodiode PD, reset transistor M1, amplification transistor M2, selection transistor M3, transfer transistor M4. The reset transistor M1 has a source, which is referred to as a sensing node FD of the pixel unit 201 by those skilled in the art.

[0075] Referring to Fig. 5, as a preferred embodiment, the CMOS image sensor also includes:

[0076] The first switch K1, the drains of the amplifying transistor M2 and the reset transistor M1 are electrically connected to the output end of the feedback unit 203 through the first switch K1, the first switch K1 recei...

no. 3 example

[0088] Please refer to FIG. 6 , which is a schematic circuit diagram of a 5T CMOS image sensor according to a third embodiment of the present invention. The CMOS image sensor includes a pixel unit 201 , a control unit 202 and a feedback unit 203 . The 5T type CMOS image sensor in the present invention refers to that the pixel unit 201 includes 1 photodiode and 5 NMOS transistors, which are respectively: photodiode PD, reset transistor M1, amplification transistor M2, selection transistor M3, transfer transistor M4, global Reset transistor M5. The reset transistor M1 has a source, and the source is called the sensing node FD of the pixel unit by those skilled in the art.

[0089] As a preferred embodiment, the CMOS image sensor also includes:

[0090] The first switch K1, the drains of the amplifying transistor M2 and the reset transistor M1 are electrically connected to the output end of the feedback unit 203 through the first switch K1, the first switch K1 receives the cont...

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Abstract

The invention provides a CMOS (Complementary Metal Oxide Semiconductor) image sensor which comprises a pixel unit, wherein the pixel unit comprises a reset transistor, a selecting transistor and an amplifying transistor; the reset transistor comprises a source electrode, and the source electrode is used as an inducing node of the pixel unit. The CMOS image sensor also comprises a reset unit, wherein the reset unit improves the potential of the inducing node to a high potential when an input first signal is the high potential and increases the channel resistance of the reset transistor when the first signal is converted into a low potential from the high potential. By increasing the conducting resistance of the reset transistor, the reset noise bandwidth is relatively reduced so that more reset noise can be removed by a negative feedback operation amplifier.

Description

technical field [0001] The present invention relates to an image sensor, in particular to a CMOS image sensor including a reset unit. Background technique [0002] Image sensors of digital color imaging devices such as video cameras, digital cameras, and digital video cameras usually use CCD (Charge-coupled device, charge-coupled device) or CMOS (Complementary Metal Oxide Semiconductor, complementary metal oxide semiconductor) technology. Image sensors using CMOS technology have become mainstream due to their advantages of low power consumption, low cost, and ease of production in standard production lines. [0003] A pixel unit of a CMOS image sensor in the prior art usually includes a photodiode and 3, 4 or 5 NMOS transistors. The CMOS image sensor may be classified into a 3T type, a 4T type, and a 5T type according to the number of transistors included in a pixel unit. The working principles of the existing 3T and 4T image sensors are the same as those of the 5T image s...

Claims

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Application Information

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IPC IPC(8): H04N5/335
Inventor 任张强
Owner BRIGATES MICROELECTRONICS KUNSHAN
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