Tunable current driver and operating method thereof

1. A tunable current driver for a flat-panel display, which comprising:

a semiconductor memory device, comprising:

a first gate electrode;

a first trapping layer disposed under the first gate electrode;

a first gate oxide layer disposed under the first trapping layer;

a first polysilicon layer disposed under the first gate oxide layer and on a glass substrate;

a first source/drain pair formed in the first polysilicon layer at opposing sides of the first gate electrode, wherein one of the first source/drain pair is electrically coupled with a lighting device;

a selective transistor comprising a second gate electrode and a second source/drain pair, wherein one of the second source/drain pair is electrically coupled with the first gate electrode, the other of the second source/drain pair is electrically coupled with a data line, and the second gate electrode is electrically coupled with a select line; and

at least one buffer layer disposed between the first polysilicon layer and the glass substrate.

2. The tunable current driver as claimed in claim 1 , wherein the first trapping layer comprises a material selected from the group consisting of SiNx, SiON, nanocrystal, and combinations thereof.

3. The tunable current driver as claimed in claim 1 , wherein the selective transistor is a NMOS.

4. The tunable current driver as claimed in claim 1 , wherein the selective transistor further comprising:

a second trapping layer disposed under the second gate electrode;

a second gate oxide layer disposed under the second trapping layer; and

a second polysilicon layer disposed under the second gate oxide layer and on a glass substrate, wherein the second source/drain pair formed in the second polysilicon layer at opposing sides of the second gate electrode.

5. The tunable current driver as claimed in claim 1 , wherein the selective transistor is a programmable PMOS.

6. The tunable current driver as claimed in claim 1 , wherein the semiconductor memory device's threshold voltage is changed by means of F-N tunneling mechanism, channel hot electron, band-to-band-tunneling mechanism or gate hole injections.

7. The tunable current driver as claimed in claim 1 , wherein the lighting device is an OLED.

8. An operating method for the tunable current driver of claim 1 , which comprising:

driving the semiconductor memory device to output a driving current;

determining whether the driving current is less than a predetermined current; and

programming the semiconductor memory device when the driving current is less than a predetermined current.

9. The operating method as claimed in claim 8 , further comprising:

amplifying the driving current and the predetermined current before determining whether the driving current is less than the predetermined current.

10. The operating method as claimed in claim 8 , wherein the predetermined current is about 1.5 μA to about 2 μA.

11. The operating method as claimed in claim 8 , wherein the step of programming the semiconductor memory device, comprising:

applying a first electrical potential to the select line;

applying a second electrical potential to the data line; and

applying a third electrical potential to the other of the first source/drain pair.

12. The operating method as claimed in claim 11 , wherein the first electrical potential minus the second electrical potential leaves about 2 Volts, and the third electrical potential is about 0 Volt.

13. The operating method as claimed in claim 11 , wherein the first electrical potential is about 25 Volt, about 30 Volt, about 35 Volt or about 40 Volt.

14. The operating method as claimed in claim 8 , further comprising:

driving a standard semiconductor memory device to output the predetermined current under the same condition as driving the semiconductor memory device.