US 2012/0056537 A1Published application

El display device and electronic device including the same

AssigneeSemiconductor Energy Laboratory Co., Ltd.

InventorJun KOYAMA

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Abstract

An object is to suppress luminance variation due to change in the amount of current flowing through a light-emitting element, caused by change in environmental temperature. A monitor circuit for compensating the cathode potential of the light-emitting element in accordance with environmental temperature is provided in the vicinity of a pixel portion in order to compensate a change in properties, due to environmental temperature, of a transistor including an oxide semiconductor layer and the light-emitting element. The monitor circuit includes a monitor power supply line, a monitor transistor including an oxide semiconductor layer, a monitor light-emitting element, a current source circuit, and an amplification circuit that compensates the cathode potential of the light-emitting element. The potential of the monitor power supply line is lower than the potential of a power supply line in the pixel.

Claims19

Dependent claims

An EL display device comprising:

a monitor circuit comprising:
a monitor power supply line,
a monitor transistor comprising a first terminal electrically connected to the monitor power supply line and a gate electrically connected to the monitor power supply line,
a monitor light-emitting element comprising a first electrode electrically connected to a second terminal of the monitor transistor,
a current source circuit electrically connected to a second electrode of the monitor light-emitting element, and
an amplification circuit comprising an input terminal electrically connected to the second electrode of the monitor light-emitting element;
and
a pixel comprising:
a light-emitting element comprising a first electrode electrically connected to an output terminal of the amplification circuit, and
a driving transistor comprising a first terminal electrically connected to a second electrode of the light-emitting element, a second terminal electrically connected to a power supply line, and a gate electrically connected to a signal line,
wherein each of the monitor transistor and the driving transistor comprises a semiconductor layer comprising an oxide semiconductor, and
wherein a potential of the monitor power supply line is lower than a potential of the power supply line.

9 more elements

An EL display device comprising:

a first monitor circuit comprising:
a first monitor power supply line,
a first monitor transistor comprising a first terminal electrically connected to the first monitor power supply line and a gate electrically connected to the first monitor power supply line,
a first monitor light-emitting element comprising a first electrode electrically connected to a second terminal of the first monitor transistor,
a first current source circuit electrically connected to a second electrode of the first monitor light-emitting element, and
a first amplification circuit comprising an input terminal electrically connected to the second electrode of the first monitor light-emitting element;
a second monitor circuit comprising:
a second monitor power supply line,
a second monitor transistor comprising a first terminal electrically connected to the second monitor power supply line and a gate electrically connected to the second monitor power supply line,
a second monitor light-emitting element comprising a first electrode electrically connected to a second terminal of the second monitor transistor,
a second current source circuit electrically connected to a second electrode of the second monitor light-emitting element, and
a second amplification circuit comprising an input terminal electrically connected to the second electrode of the second monitor light-emitting element;
a first pixel comprising:
a first light-emitting element comprising a first electrode electrically connected to an output terminal of the first amplification circuit, and
a first driving transistor comprising a first terminal electrically connected to a second electrode of the first light-emitting element, a second terminal electrically connected to a first power supply line, and a gate electrically connected to a first signal line;
and
a second pixel comprising:
a second light-emitting element comprising a first electrode electrically connected to an output terminal of the second amplification circuit, and
a second driving transistor comprising a first terminal electrically connected to a second electrode of the second light-emitting element, a second terminal electrically connected to a second power supply line, and a gate electrically connected to a second signal line,
wherein each of the first monitor transistor, the second monitor transistor, the first driving transistor, and the second driving transistor comprises a semiconductor layer comprising an oxide semiconductor,
wherein a potential of the first monitor power supply line is lower than a potential of the first power supply line, and
wherein a potential of the second monitor power supply line is lower than a potential of the second power supply line.

19 more elements

An EL display device comprising:

a monitor circuit comprising:
a monitor power supply line,
a monitor transistor comprising a first terminal electrically connected to the monitor power supply line and a gate electrically connected to the monitor power supply line,
a monitor light-emitting element comprising a first electrode electrically connected to a second terminal of the monitor transistor,
a current source circuit electrically connected to a second electrode of the monitor light-emitting element, and
an amplification circuit comprising an input terminal electrically connected to the second electrode of the monitor light-emitting element;
and
a pixel comprising:
a light-emitting element comprising a first electrode electrically connected to an output terminal of the amplification circuit, and
a driving transistor comprising a first terminal electrically connected to a second electrode of the light-emitting element, a second terminal electrically connected to a power supply line, and a gate electrically connected to a signal line,
wherein each of the monitor transistor and the driving transistor comprises a semiconductor layer comprising an oxide semiconductor,
wherein a potential of the monitor power supply line is lower than a potential of the power supply line,
wherein each of the monitor transistor and the driving transistor is formed over a first substrate, and
wherein the amplification circuit is formed over a second substrate.

11 more elements

Dependencies are inferred from the claim text.