Semiconductor device

• US 7,852,330 B2
• Filed: 06/03/2004
• Issued: 12/14/2010
• Est. Priority Date: 06/06/2003
• 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): Dinh; Duc Q
• Application Number:
  US10/859,475
• Publication Number:
  US 20050168905A1
• Time in Patent Office: 2,385 Days
• Field of Search: 345 76-102, 345/690, 345/204, 345/211
• US Class Current: 345/211
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with 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 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• 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 3/325 the data current flowing through the driving transistor during a setting phase, e.g. by using a switch for connecting the driving transistor to the data driver
• 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

Abstract

A semiconductor device is provided in which a transistor which supplies a current to a load (an EL pixel and a signal line) can supply an accurate current without being affected by a variation. A voltage of each terminal of a transistor is controlled by using a feedback circuit using an amplifier circuit. A current Idata is inputted from a current source circuit to a transistor and a gate-source voltage (a source potential) required for the transistor to flow the current Idata is set by using the feedback circuit. The feedback circuit is controlled to operate so that a drain potential of the transistor becomes a predetermined potential. Then, a gate voltage required to flow the current Idata is set. By using the set transistor, an accurate current can be supplied to the load (an EL element and a signal line). As a drain potential can be controlled, the kink effect can be reduced.

Claims

1. A semiconductor device comprising a circuit which controls by a transistor a first current to be supplied to a load,

wherein a source or a drain of the transistor is electrically connected to a current source circuit,

wherein an amplifier circuit is provided which controls a gate-source voltage and a drain-source voltage of the transistor when a second current is supplied from the current source circuit to the transistor, so that the first current to be supplied to the load flows into the transistor, and

wherein a gate of the transistor is electrically connected to an output of the amplifier circuit.

4. A semiconductor device according to claim 1, wherein the semiconductor device is used in a display portion of an electric apparatus selected from the group consisting of a light emitting device, a digital still camera, a computer, a mobile computer, an image reproducing apparatus, a goggle type display, a video camera and a portable phone.

2. A semiconductor device comprising a circuit which controls by a transistor a current to be supplied to a load,

wherein a source or a drain of the transistor is electrically connected to a current source circuit,

wherein an amplifier circuit is provided which stabilizes a gate potential of the transistor so that a drain potential of the transistor becomes a predetermined potential, and so that the current to be supplied to the load flows into the transistor, and

wherein a gate of the transistor is electrically connected to an output of the amplifier circuit.

5. A semiconductor device according to claim 2, wherein the semiconductor device is used in a display portion of an electric apparatus selected from the group consisting of a light emitting device, a digital still camera, a computer, a mobile computer, an image reproducing apparatus, a goggle type display, a video camera and a portable phone.

3. A semiconductor device comprising a circuit which controls by a transistor a current to be supplied to a load,

wherein a source or a drain of the transistor is electrically connected to a current source circuit,

wherein a feedback circuit is provided which stabilizes a gate potential of the transistor so that a drain potential of the transistor becomes a predetermined potential, and so that the current to be supplied to the load flows into the transistor, and

wherein a gate of the transistor is electrically connected to an output of the feedback circuit.

6. A semiconductor device according to claim 3, wherein the semiconductor device is used in a display portion of an electric apparatus selected from the group consisting of a light emitting device, a digital still camera, a computer, a mobile computer, an image reproducing apparatus, a goggle type display, a video camera and a portable phone.

7. A semiconductor device comprising:

a transistor having a drain electrically connected to a current source circuit;

an amplifier circuit; and

a capacitor,

wherein a first input terminal of the amplifier circuit is electrically connected to the drain of the transistor,

wherein a second input terminal of the amplifier circuit is electrically connected to a wiring,

wherein an output terminal of the amplifier circuit is electrically connected to a gate of the transistor, and

wherein a first terminal of the capacitor is electrically connected to the gate of the transistor and a second terminal of the capacitor is electrically connected to a source of the transistor.

8. A semiconductor device according to claim 7, wherein the semiconductor device is used in a display portion of an electric apparatus selected from the group consisting of a light emitting device, a digital still camera, a computer, a mobile computer, an image reproducing apparatus, a goggle type display, a video camera and a portable phone.