Display device and driving method thereof
View Patent ↗In the respect of an electrical characteristic of a transistor, a channel size W/L of a transistor is preferably designed small in order to decrease an effect of a variation in threshold voltage, while the channel size W/L is preferably designed large in order to widen a saturation region as an operation region of the transistor in the respect of characteristic of a light emitting element. Thus, decreasing an effect of a variation in threshold voltage and widening a saturation region in order not to reduce luminance due to a degradation of the light emitting element are in the relation of trade-off. According to the invention, a current capacity of a driving transistor is increased so as to operate in a wide saturation region. A lighting period control circuit is provided in each pixel for changing a lighting period of each pixel separately. Another configuration of the invention includes a plurality of transistors, for example a first driving transistor and a second driving transistor, and a lighting period control circuit for controlling a lighting period of the light emitting element in each pixel.
1. A display device comprising:
a pixel, the pixel comprising:
a first transistor comprising a first gate, a first source and a first drain;
a second transistor comprising a second gate, a second source and a second drain;
a third transistor comprising a third gate, a third source and a third drain;
a capacitor comprising a first terminal and a second terminal; and
a light emitting element,
wherein the first gate is electrically connected to a first line,
wherein one of the first source and the first drain is electrically connected to the light emitting element,
wherein one of the second source and the second drain is electrically connected to the light emitting element,
wherein the one of the first source and the first drain is directly connected to the one of the second source and the second drain,
wherein the other one of the first source and the first drain is directly connected to the other one of the second source and the second drain,
wherein the second gate is electrically connected to the first terminal,
wherein the second terminal is electrically connected to a second line,
wherein the third gate is electrically connected to a third line,
wherein one of the third source and the third drain is electrically connected to the second gate, and
wherein the other one of the third source and the third drain is electrically connected to a fourth line.
2. The display device according to claim 1 , wherein each of the first transistor and the second transistor is a p-channel transistor; and the third transistor is an n-channel transistor.
3. The display device according to claim 1 , wherein the display device is applied to an electric device selected from the group consisting of a display, a mobile computer, a game machine, a portable phone, and an electronic book reader.
4. The display device according to claim 1 , wherein at least the second transistor is a thin film transistor comprising a crystalline semiconductor film.
5. A display device comprising:
a pixel, the pixel comprising:
a first transistor comprising a first gate, a first source and a first drain;
a second transistor comprising a second gate, a second source and a second drain;
a third transistor comprising a third gate, a third source and a third drain;
a fourth transistor comprising a fourth gate, a fourth source and a fourth drain; and
a light emitting element,
wherein the first gate is electrically connected to a first line,
wherein one of the first source and the first drain is electrically connected to the light emitting element,
wherein one of the second source and the second drain is electrically connected to the light emitting element,
wherein the one of the first source and the first drain is directly connected to the one of the second source and the second drain,
wherein the other one of the first source and the first drain is directly connected to the other one of the second source and the second drain,
wherein the third gate is electrically connected to a third line,
wherein one of the third source and the third drain is electrically connected to the fourth gate,
wherein the other one of the third source and the third drain is electrically connected to a fourth line,
wherein one of the fourth source and the fourth drain is electrically connected to the other one of the first source and the first drain, and
wherein the other one of the fourth source and the fourth drain is electrically connected to a second wiring.
6. The display device according to claim 5 , wherein each of the first transistor and the second transistor is a p-channel transistor.
7. The display device according to claim 5 , wherein the display device is applied to an electric device selected from the group consisting of a display, a mobile computer, a game machine, a portable phone, and an electronic book reader.
8. The display device according to claim 5 , wherein at least the second transistor is a thin film transistor comprising a crystalline semiconductor film.
9. A display device comprising:
a pixel, the pixel comprising:
a first transistor comprising a first gate, a first source and a first drain;
a second transistor comprising a second gate, a second source and a second drain;
a third transistor comprising a third gate, a third source and a third drain;
a fourth transistor comprising a fourth gate, a fourth source and a fourth drain;
a fifth transistor comprising a fifth gate, a fifth source and a fifth drain;
a capacitor comprising a first terminal and a second terminal; and
a light emitting element,
wherein the first gate is electrically connected to a first line,
wherein one of the first source and the first drain is electrically connected to the light emitting element,
wherein one of the second source and the second drain is electrically connected to the light emitting element,
wherein the one of the first source and the first drain is directly connected to the one of the second source and the second drain,
wherein the other one of the first source and the first drain is directly connected to the other one of the second source and the second drain,
wherein the second gate is electrically connected to the first terminal,
wherein the second terminal is electrically connected to a second line,
wherein the third gate is electrically connected to a third line,
wherein one of the third source and the third drain is electrically connected to the second gate,
wherein the other one of the third source and the third drain is electrically connected to a fourth line,
wherein the fourth gate is electrically connected to the third line,
wherein one of the fourth source and the fourth drain is electrically connected to the fifth gate,
wherein the other one of the fourth source and the fourth drain is electrically connected to a fifth line,
wherein one of the fifth source and the fifth drain is electrically connected to the other one of the first source and the first drain, and
wherein the other one of the fifth source and the fifth drain is electrically connected to the second line.
10. The display device according to claim 9 , wherein each of the first transistor and the second transistor is a p-channel transistor; and the third transistor is an n-channel transistor.
11. The display device according to claim 9 , wherein the display device is applied to an electric device selected from the group consisting of a display, a mobile computer, a game machine, a portable phone, and an electronic book reader.
12. The display device according to claim 9 , wherein at least the second transistor is a thin film transistor comprising a crystalline semiconductor film.