DISPLAY DEVICE

Abstract

In the display device which is used in a miniaturized portable equipment, when a drive circuit is also connected on the same substrate as pixels, an input signal of low voltage has a level thereof shifted even when the threshold value is large or fluctuated. The display device includes pixel electrodes, switching elements which supply video signals to the pixel electrodes, and a drive circuit which supplies the video signals to the switching elements on the same substrate, wherein the drive circuit includes a level shift circuit, the level shift circuit includes a transistor. In a state that the transistor assumes an ON state, when an input signal is inputted to a source terminal and the input signal is at a low voltage level, a drain terminal assumes a low voltage level. Further, even when the input signal is at a high voltage level equal to or lower than a threshold value, the drain terminal outputs a voltage equal to or more than the threshold value as a high level voltage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing a display device of an embodiment of the present invention;

FIG. 2 is a schematic circuit diagram showing a level shift circuit of the embodiment of the present invention;

FIG. 3 is a schematic circuit diagram showing a level shift circuit of the embodiment of the present invention;

FIG. 4 is a schematic circuit diagram showing a level shift circuit of the embodiment of the present invention;

FIG. 5 is a schematic circuit diagram showing a level shift circuit of the embodiment of the present invention; and

FIG. 6 is a schematic circuit diagram showing a level shift circuit of the embodiment of the present invention.

Claims

1. A display device comprising: a display panel,a drive circuit which is formed on the display panel, anda level shift circuit which is formed on the display panel; whereinthe level shift circuit includes a transistor,an input signal is inputted to a source terminal of the transistor,the input signal has a high voltage level and a low voltage level, andthe level shift circuit outputs an output voltage equal to or more than a threshold value voltage of the transistor from a drain terminal of the transistor when the input signal is the high voltage level.

2. A display device according to claim 1, wherein the high voltage level of the input signal is equal to or less than the threshold value voltage of the transistor.

3. A display device according to claim 1, wherein an ON voltage which is equal to or more than the threshold value voltage of the transistor is supplied to a gate terminal of the transistor,a drain resistance is connected to the drain terminal to which a power source voltage is applied via the drain resistance,the high voltage level of the input signal is a lower voltage than the threshold value voltage,the output voltage is a lower voltage than the threshold value voltage which is obtained by a voltage drop of the power source voltage by a current flowing in the drain resistance when the input signal is the low voltage level, andthe output voltage is a higher voltage than the threshold value voltage which is obtained by decreasing the voltage drop in the drain resistance when the input signal is the high voltage level.

4. A display device according to claim 1, wherein the transistor is formed of poly-silicon.

5. A display device according to claim 1, wherein the transistor is brought into an ON state when an enable signal is inputted to the level shift circuit.

6. A display device comprising: a display panel,a drive circuit which is formed on the display panel,a plurality of level shift circuits which are formed on the display panel, andat least one of selection circuits which are formed on the display panel; whereinthe respective level shift circuits and the respective selection circuits include a transistor,a drain resistance is connected to a drain terminal of the transistor,the drain resistance of the respective level shift circuits has different value each other,the drain resistance of the respective selection circuits has a equal value with the drain resistance of at least one of the level shift circuits,an input signal is inputted to a source terminal of the transistor of the respective level shift circuits,Each of the plurality of level shift circuits outputs an output voltage from the drain terminal of the transistor, andat least one of the selection circuits selects the output voltage which is outputted by one of the plurality of level shift circuits.

7. A display device according to claim 6, wherein at least one of the selection circuits select the output voltage which is higher than a threshold value voltage of the transistor when the input signal is a high voltage level.