Driver circuit, display device including the driver circuit, and electronic device including the display device

• US 8,427,417 B2
• Filed: 09/08/2010
• Issued: 04/23/2013
• Est. Priority Date: 09/16/2009
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Koyama, Jun
• Primary Examiner(s): Chang, Kent
• Assistant Examiner(s): Lu, William
• Application Number:
  US12/877,705
• Publication Number:
  US 20110064186A1
• Time in Patent Office: 958 Days
• Field of Search: 345204-215, 345690-699, 345 98-100, 257/314, 257/326, 257/327, 257/348, 257/359, 257/215
• US Class Current: 345/100
• CPC Class Codes: G09G 2310/0267 Details of drivers for scan electrodes, other than drivers for liquid crystal, plasma or OLED displays
• CPC Class Codes: G09G 2310/0286 Details of a shift registers arranged for use in a driving circuit
• CPC Class Codes: G09G 2310/0289 Details of voltage level shifters arranged for use in a driving circuit
• CPC Class Codes: G09G 2310/0291 Details of output amplifiers or buffers arranged for use in a driving circuit
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G11C 19/28 using semiconductor elements G11C19/14, G11C19/36 take precedence

Abstract

A driver circuit where malfunctions in the circuit can be suppressed even when a thin film transistor is changed into an enhancement transistor or a depletion transistor is provided. In a pulse output circuit, a circuit for raising potentials of source terminals of first and second transistors from low power supply potentials is provided between the source terminals of the first and second transistors and a wiring for supplying a low power supply potential. Further, a switch for setting the potentials of the source terminals of the first and second transistors to low power supply potentials is provided. The switch is controlled by a judgment circuit for judging whether the first and second transistors are enhancement transistors or depletion transistors.

Claims

1. A driver circuit comprising plural stages of pulse output circuits, each of the pulse output circuits comprising:

a first circuit for outputting an output signal in accordance with a potential of a first node and a potential of a second node;

a second circuit for supplying a signal corresponding to an output signal from a pulse output circuit in a preceding stage to the first node;

a third circuit for intermittently supplying a signal having a high power supply potential to the second node;

a first transistor for controlling the potential of the first node in accordance with the potential of the second node; and

a second transistor for controlling the potential of the second node,

wherein the second node is electrically connected to a gate of the first transistor,

wherein the signal corresponding to the output signal from the pulse output circuit in the preceding stage is supplied to a gate of the second transistor,

wherein a fourth circuit for raising potentials of source terminals of the first and second transistors from a low power supply potential is provided between the source terminals of the first and second transistors and a wiring for supplying the low power supply potential,

wherein a switch for setting the potentials of the source terminals of the first and second transistors to a low power supply potential is provided, and

wherein the switch is controlled by a judgment circuit for judging whether the first and second transistors are enhancement transistors or depletion transistors.

2. The driver circuit according to claim 1,

wherein the fourth circuit includes a transistor,

wherein a gate and a drain terminal of the transistor are electrically connected to each other, and

wherein a source terminal of the transistor is electrically connected to a wiring to which the low power supply potential is supplied.

3. The driver circuit according to claim 2, wherein L/W of the transistor included in the fourth circuit is higher than L/W of each of the first transistor and the second transistor.

4. The driver circuit according to claim 1, wherein the judgment circuit includes a constant current source, a transistor, a comparator, and a buffer circuit.

5. The driver circuit according to claim 1, wherein the switch is a transistor.

6. The driver circuit according to claim 1, wherein the transistor includes a semiconductor layer formed using an oxide semiconductor layer.

7. A display device comprising the driver circuit according to claim 1.

8. The display device according to claim 7, wherein the display device is incorporated in one of a camera and a computer.