# US 2021/0082981 A1 · Image sensor with increased dynamic range

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- Number: US 2021/0082981 A1
- Document ID: US20210082981A1
- Status: Published application
- Kind: A1
- Application number: 17/019,075
- Filed: 2020-09-11
- Published: 2021-03-18
- Earliest claimed: 2019-09-17
- Assignees: Commissariat à I'Énergie Atomique et aux Énergies Alternatives
- Applicants: Commissariat à I'Énergie Atomique et aux Énergies Alternatives
- Inventors: François Ayel
- Web page: https://patentgrep.com/patent/US20210082981A1

## CPC

- H04N 25/57: Control of the dynamic range
- H10F 39/8037: {the integrated elements comprising a transistor}
- H04N 25/59: by controlling the amount of charge storable in the pixel, e.g. modification of the charge conversion ratio of the floating node capacitance
- H04N 25/77: Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
- H04N 25/78: Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters
- H10F 39/18: Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION

## Abstract

An image sensor including: a pixel circuit comprising a first transistor having one of its main conducting nodes connected to an output line, the other of its main conducting nodes coupled to a supply voltage rail via a read transistor, and its control node coupled to a sense node of the pixel circuit; a current source coupled to the output line; and a control circuit configured to read a pixel voltage from the pixel circuit by: activating the current source while the read transistor is non-conducting; and deactivating the current source and activating the read transistor of the pixel circuit in order to impose a boosted voltage at the sense node.

## Claims

### Claim 1

An image sensor comprising:
a pixel circuit comprising a first transistor having one of its main conducting nodes connected to an output line, the other of its main conducting nodes coupled to a supply voltage rail via a read transistor, and its control node coupled to a sense node of the pixel circuit;
a current source coupled to the output line; and
a control circuit configured to read a pixel voltage from the pixel circuit by:
activating the current source while the read transistor is non-conducting; and
deactivating the current source and activating the read transistor while the current source remains deactivated in order to impose a boosted voltage at the sense node.

### Claim 2 (depends on 1)

The image sensor of claim 1, wherein, after imposing the boosted voltage at the sense node, the control circuit is further configured to activate the current source and to transfer charge from a photodiode of the pixel circuit to the sense node.

### Claim 3 (depends on 2)

The image sensor of claim 2, wherein the pixel circuit further comprises a transfer gate coupling the photodiode to the sense node, and the control circuit is configured to transfer the charge from the photodiode to the sense node of the pixel circuit by activating the transfer gate.

### Claim 4 (depends on 1)

The image sensor of claim 1, wherein the control circuit is further configured to couple the sense node of the pixel circuit to a reset voltage rail prior to activating the read transistor.

### Claim 5 (depends on 1)

The image sensor of claim 1, wherein the pixel circuit is part of an array of pixel circuits arranged in rows and columns, a plurality of the pixel circuits of a same column being coupled to said output line.

### Claim 6 (depends on 1)

The image sensor of claim 1, wherein the current source comprises a second transistor forming a branch of a current mirror, and a third transistor configured to selectively prevent conduction of the second transistor in order to deactivate the current source.

### Claim 7 (depends on 6)

The image sensor of claim 6, wherein the third transistor is coupled in series with the second transistor.

### Claim 8 (depends on 6)

The image sensor of claim 6, wherein the third transistor is coupled between a control node of the second transistor and a further supply rail.

### Claim 9

A method of reading a pixel voltage from a pixel circuit of an image sensor, the pixel circuit comprising a first transistor having one of its main conducting nodes connected to an output line, the other of its main conducting nodes coupled to a supply voltage rail via a read transistor, and its control node coupled to a sense node of the pixel circuit, the method comprising:
activating a current source of the image sensor coupled to the output line while the read transistor is non-conducting; and
deactivating the current source and activating the read transistor while the current source remains deactivated in order to impose a boosted voltage at the sense node.

### Claim 10 (depends on 9)

The method of claim 9, further comprising, after imposing the boosted voltage at the sense node, activating the current source and transferring charge from a photodiode of the pixel circuit to the sense node.

### Claim 11 (depends on 10)

The method of claim 10, wherein the pixel circuit further comprises a transfer gate coupling the photodiode to the sense node, the method further comprising transferring charge from the photodiode to the sense node of the pixel circuit by activating the transfer gate.

### Claim 12 (depends on 9)

The method of claim 9, further comprising coupling the sense node of the pixel circuit to a reset voltage rail prior to activating the read transistor.