# US 9,006,757 B2 · Method of driving a light emitting device

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- Number: US 9,006,757 B2
- Document ID: US9006757B2
- Status: Granted
- Kind: B2
- Application number: 13/955,154
- Filed: 2013-07-31
- Published: 2013-11-28
- Granted: 2015-04-14
- Earliest claimed: 2002-04-30
- Assignees: Semiconductor Energy Laboratory Co., Ltd.
- Applicants: Semiconductor Energy Laboratory Co., Ltd.
- Inventors: Shunpei Yamazaki; Mitsuaki Osame; Jun Koyama
- Web page: https://patentgrep.com/patent/US9006757B2

## CPC

- H05B 45/395: Linear regulators
- H05B 45/60: Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
- H10D 86/441: {Interconnections, e.g. scanning lines}
- H10D 86/60: wherein the TFTs are in active matrices
- Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

The present invention is characterized in that a transistor with its L/W set to 10 or larger is employed, and that |VDS| of the transistor is set equal to or larger than 1 V and equal to or less than |VGS−Vth|. The transistor is used as a resistor so that the resistance of a light emitting element can be held by the transistor. This slows down an increase in internal resistance of the light emitting element and the resultant current value reduction. Accordingly, a change with time in light emission luminance is reduced and the reliability is improved.

## Claims

### Claim 1

A light-emitting device comprising:
a pixel including a signal line, a scanning line, a light-emitting element, a first transistor, and a second transistor over a substrate,
wherein one of source and drain of the first transistor is electrically connected to the light-emitting element, a gate of the first transistor is electrically connected to one of source and drain of the second transistor,
wherein the other of source and drain of the second transistor is electrically connected to the signal line, a gate of the second transistor is electrically connected to the scanning line,
wherein a semiconductor including a channel of the first transistor has a region extending in a first direction and a region extending in a second direction under the gate of the first transistor, and
wherein the first direction is not parallel to the second direction.

### Claim 2 (depends on 1)

The light-emitting device according to claim 1, wherein the semiconductor including the channel of the first transistor has an S-shape.

### Claim 3 (depends on 1)

The light-emitting device according to claim 1, wherein a channel length L and a channel width W of the first transistor satisfies L/W≧10.

### Claim 4 (depends on 1)

The light-emitting device according to claim 1, wherein the other of source and drain of the first transistor is electrically connected to a power supply line.

### Claim 5 (depends on 1)

The light-emitting device according to claim 1, wherein the light-emitting device is incorporated in one selected from the group consisting of a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction apparatus, a goggle type display, a video camera, and a mobile telephone.

### Claim 6

A light-emitting device comprising:
a pixel including a signal line, a scanning line, a light-emitting element, a first transistor, and a second transistor over a substrate,
wherein one of source and drain of the first transistor is electrically connected to the light-emitting element, a gate of the first transistor is electrically connected to one of source and drain of the second transistor,
wherein the other of source and drain of the second transistor is electrically connected to the signal line, a gate of the second transistor is electrically connected to the scanning line,
wherein a semiconductor including a channel of the first transistor has a region extending in a first direction and a region extending in a second direction under the gate of the first transistor, and
wherein the first direction is orthogonal to the second direction.

### Claim 7 (depends on 6)

The light-emitting device according to claim 6, wherein the semiconductor including the channel of the first transistor has an S-shape.

### Claim 8 (depends on 6)

The light-emitting device according to claim 6, wherein a channel length L and a channel width W of the first transistor satisfies L/W≧10.

### Claim 9 (depends on 6)

The light-emitting device according to claim 6, wherein the other of source and drain of the first transistor is electrically connected to a power supply line.

### Claim 10 (depends on 6)

The light-emitting device according to claim 6, wherein the light-emitting device is incorporated in one selected from the group consisting of a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction apparatus, a goggle type display, a video camera, and a mobile telephone.

### Claim 11

A light-emitting device comprising:
a transistor including a gate electrode and a channel in a semiconductor over a substrate,
wherein the semiconductor including the channel has a region extending in a first direction and a region extending in a second direction under the gate of the transistor, and
wherein the first direction is not parallel to the second direction.

### Claim 12 (depends on 11)

The light-emitting device according to claim 11, wherein the semiconductor including the channel of the transistor has an S-shape.

### Claim 13 (depends on 11)

The light-emitting device according to claim 11, wherein a channel length L and a channel width W of the first transistor satisfies L/W≧10.

### Claim 14 (depends on 11)

The light-emitting device according to claim 11, wherein the light-emitting device is incorporated in one selected from the group consisting of a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction apparatus, a goggle type display, a video camera, and a mobile telephone.

### Claim 15

A light-emitting device comprising:
a transistor including a gate electrode and a channel in a semiconductor over a substrate,
wherein the semiconductor including the channel has a region extending in a first direction and a region extending in a second direction under the gate of the transistor, and
wherein the first direction is orthogonal to the second direction.

### Claim 16 (depends on 15)

The light-emitting device according to claim 15, wherein the semiconductor including the channel of the transistor has an S-shape.

### Claim 17 (depends on 15)

The light-emitting device according to claim 15, wherein a channel length L and a channel width W of the transistor satisfies L/W≧10.

### Claim 18 (depends on 15)

The light-emitting device according to claim 15, wherein the light-emitting device is incorporated in one selected from the group consisting of a digital still camera, a lap-top computer, a mobile computer, a portable image reproduction apparatus, a goggle type display, a video camera, and a mobile telephone.