Display device and driving method thereof

1. A display device comprising:

a substrate;

a gate line formed on the substrate; and

a gate-off voltage generator that generates a gate-off voltage supplied to the gate line, wherein the gate-off voltage generator comprises:

a transistor having a base terminal, a collector terminal connected to ground, and an emitter terminal connected to the gate line, wherein the emitter terminal outputs the gate-off voltage to the gate line;

a first resistor and a second resistor connected in series between the emitter terminal and a terminal supplied with a reference voltage fixed and different from ground;

a discharge resistor between the emitter terminal and the ground; and

a controller connected to the base terminal and feedback with a feedback voltage which is a voltage of a node connected with the first resistor and the second resistor,

wherein the gate line includes a first end supplied with the gate-off voltage and a second end supplied with a second gate-off voltage and

wherein the second gate-off voltage is lower than the gate-off voltage.

2. The device of claim 1 , wherein the gate-off voltage generator is formed on the substrate.

3. The device of claim 1 , wherein the controller controls a base voltage supplied to the base terminal based upon the feedback voltage.

4. The device of claim 3 , wherein the controller is configured to:

detect the gate-off voltage based upon the feedback voltage,

compare the gate-off voltage with a first voltage, and

when the gate-off voltage is different than the first voltage, control the base voltage such that the gate-off voltage becomes the first voltage.

5. The device of claim 1 , wherein:

the gate-off voltage generator further comprises a resistor between the emitter terminal and a terminal supplied with the second gate-off voltage.

6. A driving method of a display device having a substrate, a gate line formed on the substrate, and a gate-off voltage generator that generates a gate-off voltage supplied to the gate line, wherein the gate-off voltage generator comprises a transistor having a base terminal, a collector terminal and an emitter terminal wherein the emitter terminal outputs the gate-off voltage by connecting to the gate line, a first resistor and a second resistor connected in series between the emitter terminal and the terminal supplied with a reference voltage fixed and different from ground, a discharge resistor between the emitter terminal and the ground, and a controller connected to the base terminal, the method comprising:

supplying a first end of the gate line with the gate-off voltage while supplying a second end of the gate line with a second gate-off voltage, wherein the second gate-off voltage is lower than the gate-off voltage,

feeding back a feedback voltage which is a voltage of a node connected with the first resistor and the second resistor;

detecting the gate-off voltage based upon the feedback voltage in the controller;

comparing the gate-off voltage with a first voltage in the controller; and

controlling the base voltage such that the gate-off voltage becomes the first voltage when the gate-off voltage is different from the first voltage in the controller.

7. The method of claim 6 , wherein the gate-off voltage generator is formed on the substrate.

8. A gate-off voltage generator for providing a gate-off voltage to a gate line of a display panel, comprising:

a transistor having a base terminal, a collector terminal, and an emitter terminal connected to the gate line, the emitter terminal configured to output the gate-off voltage to a first end of the gate line, a controller connected to the base terminal;

a first resistor and a second resistor connected in series between the emitter terminal and a terminal supplied with a reference voltage fixed and different from ground;

a discharge resistor between the emitter terminal and the ground; and

a feedback circuit connected between the gate line and the controller, the feedback circuit configured to provide to the controller a feedback voltage which is a voltage of a node connected with the first resistor and the second resistor, based upon the gate-off voltage outputted from the emitter terminal,

wherein a second end of the gate line is supplied with a second gate-off voltage,

wherein the gate-off voltage from the emitter terminal is compared with a desired gate-off voltage in the controller and a voltage at the base terminal is controlled by the controller to provide the desired gate-off voltage to gate line,

wherein the second gate-off voltage is lower than the gate-off voltage.