Light-emitting device and driving method thereof

• US 20040080474A1
• Filed: 10/24/2002
• Published: 04/29/2004
• Est. Priority Date: 10/26/2001
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kimura, Hajime
• Granted Patent: US 7,456,810 B2
• Time in Patent Office: Days
• US Class Current: 345/82
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H01L 27/1255 integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H01L 27/13 combined with thin-film or thick-film passive components
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 29/78672 Polycrystalline or microcrystalline silicon transistor
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/1216 the pixel elements being capacitors
• CPC Class Codes: H10K 59/123 : Connection of the pixel electrodes to the thin film transistors [TFT]
• CPC Class Codes: H10K 59/131 : Interconnections, e.g. wiring lines or terminals

Abstract

In a light emitting device, luminance irregularities caused by fluctuation in threshold of TFTs for supplying a current to EL elements among pixels hinder the light emitting device from improving the image quality. A voltage equal to the threshold of a TFT 110 is held in capacitor means 111 in advance. When a video signal is inputted from a source signal line, the voltage held in the capacitor means is added to the signal, which is then applied to a gate electrode of the TFT 110. Even when threshold is fluctuated among pixels, each threshold is held in the capacitor means 111 of each pixel, and therefore, influence of the threshold fluctuation can be removed. Since the threshold is stored in the capacitor means 111 alone and the voltage between two electrodes is not changed while a video signal is written, fluctuation in capacitance value has no influence.

Claims

1. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has at least a current supply line, first through fourth transistors, and capacitor means;

a gate electrode of the first transistor is electrically connected to a first electrode of the second transistor and to a first electrode of the capacitor means, a first electrode of the first transistor is electrically connected to the current supply line, a second electrode of the first transistor is electrically connected to a second electrode of the second transistor and to a first electrode of the third transistor;

a gate electrode of the second transistor is inputted with a first signal;

a gate electrode of the third transistor is inputted with a second signal;

a second electrode of the capacitor means is electrically connected to a first electrode of the fourth transistor; and

a gate electrode of the fourth transistor is inputted with a third signal, and a second electrode of the fourth transistor is electrically connected to the current supply line.

47. A light emitting device according to claim 1, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

66. A light emitting device according to claim 1, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

87. An electronic equipment wherein using the light emitting device of claim 1, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

2. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fourth gate signal lines, a current supply line, first through fifth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to the first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to the current supply line;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor and to a gate electrode of the fifth transistor;

a gate electrode of the third transistor is electrically connected to the third gate signal line, and a second electrode of the third transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a gate electrode of the fourth transistor is electrically connected to the fourth gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the light emitting element; and

a second gate electrode of the fifth transistor is electrically connected to the current supply line.

48. A light emitting device according to claim 2, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

67. A light emitting device according to claim 2, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

88. An electronic equipment wherein using the light emitting device of claim 2, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

3. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through third gate signal lines, a current supply line, first through fifth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to the current supply line;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor and to a gate electrode of the fifth transistor;

a gate electrode of the third transistor is electrically connected to the second gate signal line, and a second electrode of the third transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a gate electrode of the fourth transistor is electrically connected to the third gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the light emitting element; and

a second electrode of the fifth transistor is electrically connected to the current supply line.

20. A light emitting device according to claim 3, wherein the second transistor and the third transistor have the same polarity.

49. A light emitting device according to claim 3, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

68. A light emitting device according to claim 3, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

89. An electronic equipment wherein using the light emitting device of claim 3, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

4. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fourth gate signal lines, a current supply line, first through fifth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the second transistor and to a first electrode of the capacitor means;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor and to a gate electrode of the fifth transistor;

a gate electrode of the third transistor is electrically connected to the third gate signal line, and a second electrode of the third transistor is electrically connected to a second electrode of the fifth transistor and to a first electrode of the light emitting element; and

a gate electrode of the fourth transistor is electrically connected to the fourth gate signal line, a second electrode of the fourth transistor is electrically connected to the current supply line.

50. A light emitting device according to claim 4, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

69. A light emitting device according to claim 4, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

90. An electronic equipment wherein using the light emitting device of claim 4, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

5. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through third gate signal lines, a current supply line, first through fifth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the second transistor and to a first electrode of the capacitor means;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor and to a gate electrode of the fifth transistor;

a gate electrode of the third transistor is electrically connected to the second gate signal line, and a second electrode of the third transistor is electrically connected to a second electrode of the fifth transistor and to a first electrode of the light emitting element; and

a gate electrode of the fourth transistor is electrically connected to the third gate signal line, a second electrode of the fourth transistor is electrically connected to the current supply line.

21. A light emitting device according to claim 5, wherein the second transistor and the third transistor have the same polarity.

51. A light emitting device according to claim 5, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

70. A light emitting device according to claim 5, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

91. An electronic equipment wherein using the light emitting device of claim 5, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

6. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fifth gate signal lines, a current supply line, first through sixth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to the current supply line;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor and to a gate electrode of the fifth transistor;

a gate electrode of the third transistor is electrically connected to the third gate signal line, and a second electrode of the third transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a gate electrode of the fourth transistor is electrically connected to the fourth gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the light emitting element;

a second electrode of the fifth transistor is electrically connected to the current supply line; and

a gate electrode of the sixth transistor is electrically connected to the fifth gate signal line, and a first electrode of the sixth transistor is electrically connected to the first electrode of the third transistor or to the second electrode of the third transistor.

41. A light emitting device according to claim 6, wherein the second electrode of the sixth transistor is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line, or to one of the gate signal lines except the gate signal line that controls the pixel.

52. A light emitting device according to claim 6, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

71. A light emitting device according to claim 6, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

92. An electronic equipment wherein using the light emitting device of claim 6, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

7. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fourth gate signal lines, a current supply line, first through sixth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to the current supply line;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor and to a gate electrode of the fifth transistor;

a gate electrode of the third transistor is electrically connected to the second gate signal line, and a second electrode of the third transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a gate electrode of the fourth transistor is electrically connected to the third gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the light emitting element;

a second electrode of the fifth transistor is electrically connected to the current supply line; and

a gate electrode of the sixth transistor is electrically connected to the fourth gate signal line, and a first electrode of the sixth transistor is electrically connected to the first electrode of the third transistor or to the second electrode of the third transistor.

22. A light emitting device according to claim 7, wherein the second transistor and the third transistor have the same polarity.

42. A light emitting device according to claim 7, wherein the second electrode of the sixth transistor is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line, or to one of the gate signal lines except the gate signal line that controls the pixel.

53. A light emitting device according to claim 7, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

72. A light emitting device according to claim 7, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

93. An electronic equipment wherein using the light emitting device of claim 7, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

8. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fourth gate signal lines, a current supply line, first through sixth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fifth transistor and to a first electrode of the sixth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the third gate signal line, and a second electrode of the third transistor is electrically connected to a first electrode of the fourth transistor and to a second electrode of the fifth transistor;

a gate electrode of the fourth transistor is electrically connected to the fourth gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the light emitting element; and

a second electrode of the sixth transistor is electrically connected to the current supply line.

29. A light emitting device according to claim 8, wherein (W₁/L₁)>

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

54. A light emitting device according to claim 8, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

73. A light emitting device according to claim 8, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

94. An electronic equipment wherein using the light emitting device of claim 8, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

9. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through third gate signal lines, a current supply line, first through sixth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fifth transistor and to a first electrode of the sixth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the second gate signal line, and a second electrode of the third transistor is electrically connected to a first electrode of the fourth transistor and to a second electrode of the fifth transistor;

a gate electrode of the fourth transistor is electrically connected to the third gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the light emitting element; and

a second electrode of the sixth transistor is electrically connected to the current supply line.

23. A light emitting device according to claim 9, wherein the second transistor and the third transistor have the same polarity.

30. A light emitting device according to claim 9, wherein (W₁/L₁)>

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

55. A light emitting device according to claim 9, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

74. A light emitting device according to claim 9, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

95. An electronic equipment wherein using the light emitting device of claim 9, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

10. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fourth gate signal lines, a current supply line, first through sixth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fifth transistor and to a first electrode of the sixth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the third gate signal line, and a second electrode of the third transistor is electrically connected to a second electrode of the fifth transistor and to a first electrode of the light emitting element; and

a gate electrode of the fourth transistor is electrically connected to the fourth gate signal line, a first electrode of the fourth transistor is electrically connected to a second electrode of the sixth transistor, and a second electrode of the fourth transistor is electrically connected to the current supply line.

31. A light emitting device according to claim 10, wherein (W₁/L₁)>

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

56. A light emitting device according to claim 10, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

75. A light emitting device according to claim 10, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

96. An electronic equipment wherein using the light emitting device of claim 10, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

11. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through third gate signal lines, a current supply line, first through sixth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fifth transistor and to a first electrode of the sixth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the second gate signal line, and a second electrode of the third transistor is electrically connected to a second electrode of the fifth transistor and to a first electrode of the light emitting element; and

a gate electrode of the fourth transistor is electrically connected to the third gate signal line, a first electrode of the fourth transistor is electrically connected to a second electrode of the sixth transistor, and a second electrode of the fourth transistor is electrically connected to the current supply line.

24. A light emitting device according to claim 11, wherein the second transistor and the third transistor have the same polarity.

32. A light emitting device according to claim 11, wherein (W₁/L₁)>

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

57. A light emitting device according to claim 11, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

76. A light emitting device according to claim 11, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

97. An electronic equipment wherein using the light emitting device of claim 11, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

12. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fourth gate signal lines, a current supply line, first through sixth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the third gate signal line, and a second electrode of the third transistor is electrically connected to a second electrode of the fifth transistor and to a first electrode of the light emitting element;

a gate electrode of the fourth transistor is electrically connected to the fourth gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the sixth transistor; and

a second electrode of the sixth transistor is electrically connected to the current supply line.

33. A light emitting device according to claim 12, wherein (W₁/L₁)>

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

58. A light emitting device according to claim 12, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

77. A light emitting device according to claim 12, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

98. An electronic equipment wherein using the light emitting device of claim 12, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

13. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through third gate signal lines, a current supply line, first through sixth transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the second gate signal line, and a second electrode of the third transistor is electrically connected to a second electrode of the fifth transistor and to a first electrode of the light emitting element;

a gate electrode of the fourth transistor is electrically connected to the third gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the sixth transistor; and

a second electrode of the sixth transistor is electrically connected to the current supply line.

25. A light emitting device according to claim 13, wherein the second transistor and the third transistor have the same polarity.

34. A light emitting device according to claim 13, wherein (W₁/L₁)>

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

59. A light emitting device according to claim 13, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

78. A light emitting device according to claim 13, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

99. An electronic equipment wherein using the light emitting device of claim 13, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

14. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fifth gate signal lines, a current supply line, first through seventh transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fifth transistor and to a first electrode of the sixth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the third gate signal line, and a second electrode of the third transistor is electrically connected to a second electrode of the fifth transistor and to a first electrode of the light emitting element;

a gate electrode of the fourth transistor is electrically connected to the fourth gate signal line, a first electrode of the fourth transistor is electrically connected to a second electrode of the sixth transistor, and a second electrode of the fourth transistor is electrically connected to the current supply line; and

a gate electrode of the seventh transistor is electrically connected to the fifth gate signal line, and a first electrode of the seventh transistor is electrically connected to the first electrode of the third transistor or to the second electrode of the third transistor.

35. A light emitting device according to claim 14, wherein (W₁/L₁)>

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

43. A light emitting device according to claim 14, wherein the second electrode of the seventh transistor is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line, or to one of the gate signal lines except the gate signal line that controls the pixel.

60. A light emitting device according to claim 14, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

79. A light emitting device according to claim 14, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

100. An electronic equipment wherein using the light emitting device of claim 14, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

15. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fourth gate signal lines, a current supply line, first through seventh transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fifth transistor and to a first electrode of the sixth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the second gate signal line, and a second electrode of the third transistor is electrically connected to a second electrode of the fifth transistor and to a first electrode of the light emitting element;

a gate electrode of the fourth transistor is electrically connected to the third gate signal line, a first electrode of the fourth transistor is electrically connected to a second electrode of the sixth transistor, and a second electrode of the fourth transistor is electrically connected to the current supply line; and

a gate electrode of the seventh transistor is electrically connected to the fourth gate signal line, and a first electrode of the seventh transistor is electrically connected to the first electrode of the third transistor or to the second electrode of the third transistor.

26. A light emitting device according to claim 15, wherein the second transistor and the third transistor have the same polarity.

36. A light emitting device according to claim 15, wherein (W₁/L₁)>

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

44. A light emitting device according to claim 15, wherein the second electrode of the seventh transistor is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line, or to one of the gate signal lines except the gate signal line that controls the pixel.

61. A light emitting device according to claim 15, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

80. A light emitting device according to claim 15, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

101. An electronic equipment wherein using the light emitting device of claim 15, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

16. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fifth gate signal lines, a current supply line, first through seventh transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the third gate signal line, and a second electrode of the third transistor is electrically connected to a second electrode of the fifth transistor and to a first electrode of the light emitting element;

a gate electrode of the fourth transistor is electrically connected to the fourth gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the sixth transistor;

a second electrode of the sixth transistor is electrically connected to the current supply line; and

a gate electrode of the seventh transistor is electrically connected to the fifth gate signal line, and a first electrode of the seventh transistor is electrically connected to the first electrode of the third transistor or to the second electrode of the third transistor.

37. A light emitting device according to claim 16, wherein (W₁/L₁)>

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

45. A light emitting device according to claim 16, wherein the second electrode of the seventh transistor is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line, or to one of the gate signal lines except the gate signal line that controls the pixel.

62. A light emitting device according to claim 16, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

81. A light emitting device according to claim 16, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

102. An electronic equipment wherein using the light emitting device of claim 16, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

17. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fourth gate signal lines, a current supply line, first through seventh transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the capacitor means and to a first electrode of the second transistor;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the second gate signal line, and a second electrode of the third transistor is electrically connected to a second electrode of the fifth transistor and to a first electrode of the light emitting element;

a gate electrode of the fourth transistor is electrically connected to the third gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the sixth transistor;

a second electrode of the sixth transistor is electrically connected to the current supply line; and

a gate electrode of the seventh transistor is electrically connected to the fourth gate signal line, and a first electrode of the seventh transistor is electrically connected to the first electrode of the third transistor or to the second electrode of the third transistor.

27. A light emitting device according to claim 17, wherein the second transistor and the third transistor have the same polarity.

38. A light emitting device according to claim 17, wherein (W₁/L₁)>

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

46. A light emitting device according to claim 17, wherein the second electrode of the seventh transistor is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line, or to one of the gate signal lines except the gate signal line that controls the pixel.

63. A light emitting device according to claim 17, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

82. A light emitting device according to claim 17, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

103. An electronic equipment wherein using the light emitting device of claim 17, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

18. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fifth gate signal lines, a current supply line, first through seventh transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the second transistor, to a first electrode of the sixth transistor, and to a first electrode of the capacitor means;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to the current supply line;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode and second electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the third gate signal line, and a second electrode of the third transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a gate electrode of the fourth transistor is electrically connected to the fourth gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the light emitting element;

a second electrode of the fifth transistor is electrically connected to the current supply line; and

the seventh transistor is placed between the second electrode of the first transistor and the first electrode of the sixth transistor, or between the first electrode of the third transistor and the second electrode of the sixth transistor, or between the first electrode of the third transistor and the gate electrode of the sixth transistor, and a gate electrode of the seventh transistor is electrically connected to the fifth gate signal line.

39. A light emitting device according to claim 18, wherein (W₁/L₁)<

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

64. A light emitting device according to claim 18, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

83. A light emitting device according to claim 18, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

104. An electronic equipment wherein using the light emitting device of claim 18, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

19. A light emitting device having a pixel with a light emitting element, wherein:

the pixel has a source signal line, first through fourth gate signal lines, a current supply line, first through seventh transistors, capacitor means, and the light emitting element;

a gate electrode of the first transistor is electrically connected to the first gate signal line, a first electrode of the first transistor is electrically connected to the source signal line, and a second electrode of the first transistor is electrically connected to a first electrode of the second transistor, to a first electrode of the sixth transistor, and to a first electrode of the capacitor means;

a gate electrode of the second transistor is electrically connected to the second gate signal line, and a second electrode of the second transistor is electrically connected to the current supply line;

a second electrode of the capacitor means is electrically connected to a first electrode of the third transistor, to a gate electrode of the fifth transistor, and to a gate electrode and second electrode of the sixth transistor;

a gate electrode of the third transistor is electrically connected to the second gate signal line, and a second electrode of the third transistor is electrically connected to a first electrode of the fourth transistor and to a first electrode of the fifth transistor;

a gate electrode of the fourth transistor is electrically connected to the third gate signal line, a second electrode of the fourth transistor is electrically connected to a first electrode of the light emitting element;

a second electrode of the fifth transistor is electrically connected to the current supply line; and

the seventh transistor is placed between the second electrode of the first transistor and the first electrode of the sixth transistor, or between the first electrode of the third transistor and the second electrode of the sixth transistor, or between the first electrode of the third transistor and the gate electrode of the sixth transistor, and a gate electrode of the seventh transistor is electrically connected to the fourth gate signal line.

28. A light emitting device according to claim 19, wherein the second transistor and the third transistor have the same polarity.

40. A light emitting device according to claim 19, wherein (W₁/L₁)<

(W₂/L₂) is satisfied when the gate length of the fifth transistor is given as L₁, the channel width thereof as W₁, the gate length of the sixth transistor as L₂, and the channel width thereof as W₂.

65. A light emitting device according to claim 19, wherein a second electrode of the light emitting element is electrically connected to a power supply line that has an electric potential different from the electric potential of the current supply line.

84. A light emitting device according to claim 19, wherein:

the pixel has capacitor storage means; and

a first electrode of the capacitor storage means is electrically connected to the second electrode of the first transistor, and a second electrode of the capacitor storage means receives a constant electric potential to hold a video signal inputted from the source signal line.

105. An electronic equipment wherein using the light emitting device of claim 19, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

85. A method of driving a light emitting device having a pixel with a light emitting element,

the pixel having a source signal line, a current supply line, a transistor for supplying a desired current to the light emitting element, the light emitting element, and capacitor means, the method comprising:

a first step of accumulating electric charges in the capacitor means;

a second step of making a voltage between two electrodes of the capacitor means into a voltage equal to the threshold voltage of the transistor;

a third step of inputting a video signal from the source signal line; and

a fourth step of adding the threshold voltage to the electric potential of the video signal and applying it to a gate electrode of the transistor, so that a current is supplied to the light emitting element through the transistor and light is emitted, wherein;

the voltage between the two electrodes of the capacitor means is constant in at least the third step; and

the first transistor is turned non-conductive in at least the first and second steps.

106. An electronic equipment wherein using a method of driving a light emitting device of claim 85, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.

86. A method of driving a light emitting device having a pixel with a light emitting element,

the pixel having at least a current supply line, first through third transistors, and capacitor means,

the first transistor having a gate electrode that is electrically connected to a first electrode of the second transistor and to a first electrode of the capacitor means, the first transistor having a first electrode that is electrically connected to the current supply line, the first transistor having a second electrode that is electrically connected to a second electrode of the second transistor and to a first electrode of the third transistor,

the second transistor having a gate electrode through which a first signal is inputted,

the third transistor having a gate electrode through which a second signal is inputted,

the capacitor means having a second electrode which is electrically connected to a first electrode of the fourth transistor and through which a video signal is inputted,

the fourth transistor having a gate electrode through which a third signal is inputted, the fourth transistor having a second electrode that is electrically connected to the current supply line, the method comprising:

a first step of turning the second through fourth transistors conductive by inputting the first through third signals to thereby accumulate electric charges in the capacitor means;

a second step of turning the third transistor non-conductive and turning the second and fourth transistors conductive by inputting the first and third signals to thereby make a voltage held in the capacitor means into a voltage equal to the threshold voltage of the first transistor;

a third step of turning the second through fourth transistors non-conductive and inputting the video signal through the second electrode of the capacitor means; and

a fourth step of turning the second and fourth transistors non-conductive and turning the third transistor conductive by inputting the second signal to thereby cause a current flow between the source and drain of the first and third transistors, wherein;

the voltage between the two electrodes of the capacitor means is constant in at least the third step.

107. An electronic equipment wherein using a method of driving a light emitting device of claim 86, the electronic equipment being chosen from the group consisting of a video camera, a digital camera, a goggle type display, a navigation system, an audio reproducing device, a notebook personal computer, a game machine, a mobile computer, a cellular phone, and a DVD player.