1. Field of the Invention
The invention relates to an active matrix type display apparatus and a driving device of a load which are used for a television receiver, monitors of a computer, a cellular phone, a digital camera, a digital video camera (camcorder), and the like, an exposure device for an electrophotography printer, an exposure light source for a photolithography, and the like. More particularly, the invention relates to an active matrix type display apparatus (or device) and a driving device (or apparatus) of an active device as a load which are preferably used for a current driving type display device.
2. Related Background Art
As an active matrix electroluminescent display device, for example, there is a device disclosed in JP-A-2002-517806. FIG. 12 is a circuit diagram of a conventional pixel circuit.
The circuit shown in FIG. 12 operates as follows. Switches (transistors) 37 and 32 are closed. A switch (transistor) 33 is opened. An input signal Iin corresponding to a device current necessary for light emission of an electroluminescent device 20 as an active device is inputted. A voltage across a capacitor 38 in a stationary state becomes a gate-source voltage necessary to drive a current flowing in a channel of a drive transistor 30. When the switches 37 and 32 are opened, the gate-source voltage which is determined in accordance with the input signal Iin is held in the capacitor 38.
Subsequently, when the switch 33 is closed, a drive current according to a level of the holding voltage flows in the electroluminescent device 20 through the drive transistor 30, so that light is emitted. Reference numeral 34 denotes a power line for setting a voltage (V2) on the anode side of the electroluminescent device 20 and 31 indicates a power line for setting a voltage (V1) on the source side of the transistor.
In JP-A-2002-517806, there is such a disclosure that n-type MOS transistors are used as transistors 32, 37, and 30 and a p-type MOS transistor is used as a transistor 33.
There is also known a pixel circuit in which a p-type MOS transistor is used as a drive transistor and a p-type MOS transistor is used as a switching transistor for short-circuiting a circuit between a gate and a drain of the drive transistor. (Refer to the Official Gazette of International Publication No. WO01/91094.)
In the active matrix type display device and the driving apparatus of the active device, there is still a room to be improved from two viewpoints in which the drive current in the dark state is set to zero and a fluctuation of the drive current due to an unnecessary leakage current is prevented.