Semiconductor device

• US 8,378,578 B2
• Filed: 03/23/2011
• Issued: 02/19/2013
• Est. Priority Date: 09/21/2001
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kimura, Hajime
• Primary Examiner(s): VU, JIMMY T
• Application Number:
  US13/069,427
• Publication Number:
  US 20110169008A1
• Time in Patent Office: 699 Days
• Field of Search: 3151691-1694, 345/33, 345/44, 345/46, 345/48, 345 76- 84, 345/92, 345/204, 345211-214
• US Class Current: 315/169.1
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• 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 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements
• CPC Class Codes: H01L 27/088 the components being field-effect transistors with insulated gate
• CPC Class Codes: H01L 27/15 including semiconductor components having potential barriers, specially adapted for light emission

Abstract

A light emitting device capable of performing signal electric current write-in operations at high speed and without dispersion in the characteristics of TFTs structuring pixels influencing the brightness of light emitting elements is provided. The gate length L of a transistor in which an electric current flows during write-in of a signal electric current is made shorter than the gate length L of a transistor in which electric current supplied to EL elements flows during light emission, and high speed write-in is thus performed by having a larger electric current flow than the electric current flowing in conventional EL elements. A converter and driver transistor (108) is used for signal write-in. By using the converter and driver transistor (108) and a driver transistor (107) when supplying electric current to a light emitting element during light emission, dispersion in the transistor characteristics can be made to have less influence on brightness than when using a structure in which write-in operations and light emission operations are performed using different transistors.

Claims

1. A semiconductor device comprising:

a first transistor having a first gate, a first source, and a first drain;

a second transistor having a second gate, a second source, and a second drain;

a third transistor having a third gate, a third source, and a third drain;

a fourth transistor having a fourth gate, a fourth source, and a fourth drain;

a capacitor having a first electrode and a second electrode; and

an EL element,

wherein one of the first source and the first drain is electrically connected to one of the second source and the second drain,

wherein one of the first source and the first drain is electrically connected to one of the fourth source and the fourth drain,

wherein the first gate is electrically connected to the second gate,

wherein the first gate is electrically connected to one of the first electrode and the second electrode,

wherein the first gate is electrically connected to one of the third source and the third drain,

wherein the other one of the third source and the third drain is electrically connected to the other one of the fourth source and the fourth drain,

wherein the other one of the first source and the first drain is electrically connected to the other one of the first electrode and the second electrode, and

wherein the other one of the first source and the first drain is electrically connected to the EL element.

2. The semiconductor device according to claim 1, wherein a first electric current flows through the first transistor and does not flow through the second transistor during write-in.

3. The semiconductor device according to claim 1, wherein a first electric current flows through the first transistor during write-in, and

wherein a second electric current flows through the first transistor during light emission.

4. The semiconductor device according to claim 1, wherein an electric current flows through the first transistor and the second transistor during light emission.

5. The semiconductor device according to claim 1, wherein the first transistor and the second transistor have a same polarity.

6. The semiconductor device according to claim 1,

wherein the third gate is electrically connected to a first gate signal line, and

wherein the fourth gate is electrically connected to a second gate signal line.

7. The semiconductor device according to claim 1, wherein the semiconductor device is applied to an electronic equipment selected from the group consisting of an organic light emitting display device, a digital still camera, a laptop computer, a mobile computer, an image reproduction apparatus including a recording medium, a goggle type display, a video camera and a mobile phone.

8. A semiconductor device comprising:

a first transistor having a first gate, a first source, and a first drain;

a second transistor having a second gate, a second source, and a second drain;

a third transistor having a third gate, a third source, and a third drain;

a fourth transistor having a fourth gate, a fourth source, and a fourth drain;

a capacitor having a first electrode and a second electrode; and

an EL element,

wherein one of the first source and the first drain is electrically connected to one of the second source and the second drain, wherein one of the first source and the first drain is electrically connected to one of the fourth source and the fourth drain,

wherein one of the first source and the first drain is electrically connected to one of the third source and the third drain,

wherein the first gate is electrically connected to the second gate, wherein the first gate is electrically connected to one of the first electrode and the second electrode,

wherein the first gate is electrically connected to the other one of the third source and the third drain,

wherein the other one of the first source and the first drain is electrically connected to the other one of the first electrode and the second electrode, and

wherein the other one of the first source and the first drain is electrically connected to the EL element.

9. The semiconductor device according to claim 8, wherein a first electric current flows through the first transistor and does not flow through the second transistor during write-in.

10. The semiconductor device according to claim 8, wherein a first electric current flows through the first transistor during write-in, and

wherein a second electric current flows through the first transistor during light emission.

11. The semiconductor device according to claim 8, wherein the first transistor and the second transistor have a same polarity.

12. The semiconductor device according to claim 8,

wherein the third gate is electrically connected to a first gate signal line, and

wherein the fourth gate is electrically connected to a second gate signal line.

13. The semiconductor device according to claim 8, wherein the semiconductor device is applied to an electronic equipment selected from the group consisting of an organic light emitting display device, a digital still camera, a laptop computer, a mobile computer, an image reproduction apparatus including a recording medium, a goggle type display, a video camera and a mobile phone.

14. The semiconductor device according to claim 8, wherein a second electric current flows through the first transistor and the second transistor during light emission.