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US 8,552,948 B2Granted
Display device comprising threshold control circuit
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorsHiroyuki Miyake, Atsushi Umezaki
Life of this patent
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Abstract
The display device includes an output circuit, a threshold control circuit which sequentially selects one of a forward bias voltage and a reverse bias voltage, and a power supply control circuit which applies one of the forward bias voltage and the reverse bias voltage which is selected to a gate of a transistor included in the output circuit. Time in which the reverse bias voltage is applied to the gate of the transistor is determined in accordance with time in which the forward bias voltage is applied to the gate of the transistor.
Claims24
A display device comprising:
- a pixel comprising a first transistor;
- an output circuit comprising a second transistor, one of a source and a drain of the second transistor is electrically connected to a gate of the first transistor through a scan line;
- a power supply control circuit configured to apply one of a first voltage and a second voltage to a gate of the second transistor, and
- a threshold control circuit configured to control the power supply control circuit,
- wherein the other of the source and the drain of the second transistor is electrically and directly connected to a wiring supplied with a third voltage,
- wherein the third voltage is higher than the first voltage and lower than the second voltage, and
- wherein the threshold control circuit includes a measurement circuit configured to measure first time during which the second voltage is applied to the gate of the second transistor so that a forward bias voltage is applied to the second transistor, and an arithmetic circuit configured to calculate second time during which the first voltage is applied to the gate of the second transistor using the first time so that a reverse bias voltage is applied to the second transistor,
- wherein a threshold voltage of the second transistor shifts in a reverse direction by applying the reverse bias voltage, and
- wherein the reverse direction is opposite to a positive direction in which the threshold voltage of the second transistor shifts by applying the forward bias voltage.
6 more elements
A display device comprising:
- an output circuit comprising a transistor, one of a source and a drain of the transistor is electrically connected to a scan line;
- a power supply control circuit configured to apply one of a first voltage and a second voltage to a gate of the transistor, and
- a threshold control circuit configured to control the power supply control circuit,
- wherein the other of the source and the drain of the transistor is electrically and directly connected to a wiring supplied with a third voltage,
- wherein the third voltage is higher than the first voltage and lower than the second voltage, and
- wherein the threshold control circuit includes a measurement circuit configured to measure first time during which the second voltage is selected so that a forward bias voltage is applied to the transistor, and an arithmetic circuit configured to calculate second time during which the first voltage is selected using the first time so that a reverse bias voltage is applied to the transistor,
- wherein a threshold voltage of the transistor shifts in a reverse direction by applying the reverse bias voltage, and
- wherein the reverse direction is opposite to a positive direction in which the threshold voltage of the transistor shifts by applying the forward bias voltage.
5 more elements
A display device comprising:
- a pixel comprising a first transistor;
- an output circuit comprising a second transistor, one of a source and a drain of the second transistor is electrically connected to a gate of the first transistor through a scan line;
- a power supply control circuit configured to apply one of a first voltage and a second voltage to a gate of the second transistor , and
- a threshold control circuit configured to control the power supply control circuit,
- wherein the other of the source and the drain of the second transistor is electrically and directly connected to a wiring supplied with a third voltage,
- wherein the third voltage is higher than the first voltage and lower than the second voltage, and
- wherein the threshold control circuit includes a measurement circuit configured to measure first time during which the second voltage is applied to the gate of the second transistor so that a forward bias voltage is applied to the second transistor, a memory in which data is to be used to calculate second time during which the first voltage is applied to the gate of the second transistor from the first time is stored, and an arithmetic circuit configured to calculate the second time using the first time and the data so that a reverse bias voltage is applied to the second transistor,
- wherein a threshold voltage of the second transistor shifts in a reverse direction by applying the reverse bias voltage, and
- wherein the reverse direction is opposite to a positive direction in which the threshold voltage of the second transistor shifts by applying the forward bias voltage.
6 more elements
A display device comprising:
- an output circuit comprising a transistor, one of a source and a drain of the transistor is electrically connected to a scan line;
- a power supply control circuit configured to apply one of a first voltage and a second voltage to a gate of the transistor, and
- a threshold control circuit configured to control the power supply control circuit,
- wherein the other of the source and the drain of the transistor is electrically and directly connected to a wiring supplied with a third voltage,
- wherein the third voltage is higher than the first voltage and lower than the second voltage, and
- wherein the threshold control circuit includes a measurement circuit configured to measure first time during which the second voltage is selected so that a forward bias voltage is applied to the transistor, a memory in which data is to be used to calculate second time during which the first voltage is selected from the first time is stored, and an arithmetic circuit configured to calculate the second time using the first time and the data so that a reverse bias voltage is applied to the transistor,
- wherein a threshold voltage of the transistor shifts in a reverse direction by applying the reverse bias voltage, and
- wherein the reverse direction is opposite to a positive direction in which the threshold voltage of the transistor shifts by applying the forward bias voltage.
5 more elements
Dependencies are inferred from the claim text.