Shift register circuit and method of operating the same

1. A shift register circuit, comprising:

an OR-gate unit for receiving a start pulse or an output of a previous stage and a feedback signal;

a level shift unit for level-shifting a swing voltage of a clock signal in response to an output signal of an inverter circuit of the OR-gate unit; and

a buffer for transferring an output of the level shift unit to a next stage as an input signal,

wherein the OR-gate unit includes an NOR-gate circuit and an inverter circuit serially connected to the NOR-gate circuit,

wherein the NOR-gate circuit includes two PMOS transistors (T 1 , T 2 ) connected in serial and two NMOS transistors (T 3 , T 4 ) connected in parallel which are connected to the two PMOS transistors in serial, and the inverter circuit includes an NMOS transistor (T 5 ) and a PMOS transistor (T 6 ), and

wherein the level shift unit includes a plurality of NMOS transistors and a plurality of PMOS transistors, and a predetermined bias voltage is additionally applied to the level shift unit.

2. The shift register circuit according to claim 1 , wherein the clock signal is one of two-phase clock signals and the two-phase clock signals are complementary to each other.

3. The shift register circuit according to claim 2 , wherein the two-phase clock signals have a swing voltage lower than 10V and are inputted from an external circuit.

4. The shift register circuit according to claim 1 , wherein the feedback signal is a signal outputted from a first inverter in the buffer after the clock signal is inputted to the level shift unit.

5. The shift register circuit according to claim 1 , wherein the output signal of the OR-gate unit is generated by inputting the feedback signal to the T 1 and T 4 , inputting the start pulse to T 2 and T 3 , and passing the outputs through the T 5 and T 6 .

6. The shift register circuit according to claim 1 , wherein the level shift unit operates only when the OR-gate unit generates a high state.

7. The shift register circuit according to claim 1 , wherein the buffer includes a plurality of inverter circuits connected in a cascade form and an output of a first inverter circuit is feed-backed to a transistor of the OR-gate unit.

8. A method of operating a shift register circuit, comprising:

inputting a start pulse or an output of a previous stage and a feedback signal to an OR-gate unit;

defining an operating period by an output signal of the OR-gate unit and level-shifting a swing voltage of a clock signal by a level shift unit; and

transferring an output of the level shift unit to a next state using a buffer, wherein the OR-gate unit includes an NOR-gate circuit and an inverter circuit serially connected to the NOR-gate circuit,

wherein the NOR-gate circuit includes two PMOS transistors (T 1 , T 2 ) connected in serial and two NMOS transistors (T 3 , T 4 ) connected in parallel which are connected to the two PMOS transistors in serial, and the inverter circuit includes an NMOS transistor (T 5 ) and a PMOS transistor (T 6 ), and

wherein the level shift unit includes a plurality of NMOS transistors and a plurality of PMOS transistors, and a predetermined bias voltage is additionally applied to the level shift unit.

9. The method according to claim 8 , wherein the clock signal is one of two-phase clock signals and the two-phase clock signals are complementary to each other.

10. The method according to claim 9 , wherein the two-phase clock signals have a swing voltage lower than 10V and are inputted from an external circuit.

11. The method according to claim 8 , wherein the feedback signal is a signal outputted from a first inverter in the buffer after the clock signal is inputted to the level shift unit.

12. The method according to claim 8 , wherein the level shift unit operates only when the OR-gate unit generates a high state.