Light Emitting Device, Method of Driving a Light Emitting Device, Element Substrate, and Electronic Equipment
AssigneeSemiconductor Energy Laboratory Co., Ltd.
InventorHajime Kimura
Life of this patent
Estimating the term…
Abstract
A display device capable of obtaining a constant luminance without being influenced by temperature change is provided as well as a method of driving the display device. A current mirror circuit composed of a first transistor and a second transistor is provided in each pixel. The first transistor and second transistor of the current mirror circuit are connected such that their drain currents are kept almost equal irrespective of the level of load resistance. By controlling the OLED drive current using the current mirror circuit, a change in OLED drive current due to fluctuation in characteristics between transistors is avoided and a constant luminance is obtained without being influenced by temperature change.
Claims22
A light emitting device comprising:
- a first transistor having a first gate, a first source, and a first drain;
- a second transistor having a second gate electrically connected to the first gate, a second source electrically connected to the first source, and a second drain;
- wherein the first drain is electrically connected to the second drain in a first period, and
- wherein the second drain is electrically connected to a light emitting element in a second period.
A light emitting device comprising:
- a first transistor having a first gate, a first source, and a first drain;
- a second transistor having a second gate electrically connected to the first gate, a second source electrically connected to the first source, and a second drain;
- a third transistor having third source and drain, wherein one of the third source and drain is electrically connected to the first drain;
- a fourth transistor having fourth source and drain, wherein one of the fourth source and drain is electrically connected to the first and second gates;
- a fifth transistor having fifth source and drain, wherein one of the fifth source and drain is electrically connected to the first drain, and another one of fifth source and drain is electrically connected to the second drain;
- a sixth transistor having sixth source and drain, wherein one of the sixth source and drain is electrically connected to the second drain;
- and
- a light emitting element electrically connected to another one of the sixth source and drain.
A method of driving a light emitting device comprising steps of:
- wherein a first transistor having a first gate, a first source, and a first drain, and a second transistor having a second gate electrically connected to the first gate, a second source, and a second drain, and
- wherein the first and second drains are electrically connected to a first terminal;
- and the first and second sources are electrically connected to a second terminal,
- flowing a signal current Ic between the first and second terminals in accordance with inputting a video signal to the first terminal, wherein the signal current Ic causes a drain current I1 flowing between the first source and drain and a drain current I2 flowing between the second source and drain, in a first period;
- and
- supplying the drain current I2 to a light emitting element through the second transistor in a second period.
A light emitting device comprising:
- a first transistor having a first gate, a first source, and a first drain;
- a second transistor having a second gate electrically connected to the first gate, a second drain electrically connected to the first drain, and a second source;
- wherein the first source is electrically connected to the second source in a first period, and
- wherein the second drain is electrically connected to a light emitting element in a second period.
A light emitting device comprising:
- a first transistor having a first gate, a first source, and a first drain;
- a second transistor having a second gate electrically connected to the first gate, a second drain electrically connected to the first drain, and a second source;
- a third transistor having third source and drain, wherein one of the third source and drain is electrically connected to the first source;
- a fourth transistor having fourth source and drain, wherein one of the fourth source and drain is electrically connected to the first and second gates;
- a fifth transistor having fifth source and drain, wherein one of the fifth source and drain is electrically connected to the first source, and another one of fifth source and drain is electrically connected to the second source;
- a sixth transistor having sixth source and drain, wherein one of the sixth source and drain is electrically connected to the second source;
- and
- a light emitting element electrically connected to another one of the sixth source and drain.
Dependencies are inferred from the claim text.