Abstract:
An emission control line driver is capable of securing the stability of an output and of freely controlling the width of emission control signals. The emission control line driver includes a plurality of stages respectively coupled to emission control lines. Each of the stages includes a plurality of transistors that are configured to output the emission control signal. The width of the emission control signal may be controlled to correspond to the width of a start signal. Furthermore, a circuit structure of the stages is simplified.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2011-0001419, filed on Jan. 6, 2011, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    Aspects of embodiments according to the present invention relate to an emission control line driver and an organic light emitting display using the same. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, various flat panel displays (FPDs) with reduced weight and volume as compared to cathode ray tube (CRT) displays have been developed. The FPDs include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an organic light emitting display. 
         [0006]    Among the FPDs, the organic light emitting display displays an image using organic light emitting diodes (OLEDs) that generate light by re-combination of electrons and holes. The organic light emitting display has a fast response speed and is driven with low power consumption. A typical organic light emitting display supplies current corresponding to data signals to the OLEDs by using transistors formed in pixels so that light is emitted by the OLEDs. 
         [0007]    The typical organic light emitting display includes a data driver for supplying the data signals to data lines, a scan driver for sequentially supplying scan signals to scan lines, an emission control line driver for supplying emission control signals to emission control lines, and a display unit including a plurality of pixels coupled to the data lines, the scan lines, and the emission control lines. 
         [0008]    The pixels included in the display unit are selected, when the scan signals are supplied to the scan lines, to receive the data signals from the data lines. The pixels that receive the data signals generate light with brightness (e.g., predetermined brightness) corresponding to the data signals and display a predetermined image. Here, the emission times of the pixels are controlled by the emission control signals that are supplied from the emission control lines. In general, the emission control signals are supplied to overlap the scan signals that are supplied to one scan line or two scan lines to set the pixels, to which the data signals are supplied, in a non-emission state. 
         [0009]    Therefore, the emission control line driver includes stages coupled to the emission control lines. The stages receive at least four clock signals and output high or low voltages to output lines. 
         [0010]    However, since the stages included in the typical emission control line driver are driven by at least four clock signals, a large number of transistors are included. Therefore, manufacturing cost increases and it is difficult to secure the reliability of driving. In addition, when the emission control line driver is formed of a PMOS transistor, a low level output is unstable. 
         [0011]    To be specific, when a low signal is supplied to an emission control line, the gate electrode of the transistor that outputs the low signal is maintained at a lower voltage than the low signal. However, the voltage of the gate electrode of the transistor increases due to leakage current and the output of the low signal is unstable. 
       SUMMARY 
       [0012]    Accordingly, embodiments of the present invention are directed toward an emission control line driver capable of securing the stability of an output and of freely controlling the width of emission control signals, and an organic light emitting display using the same. 
         [0013]    According to an embodiment of the present invention, there is provided an emission control line driver including a plurality of stages. Each of the stages includes a first transistor coupled between a first output terminal and a first power source, the first transistor being configured to be turned on or off to correspond to a voltage applied to a first node that is coupled to a gate electrode of the first transistor, a second transistor coupled between the first output terminal and a second power source that outputs a voltage that is lower than the first power source, the second transistor being configured to be turned on or off to correspond to a voltage applied to a second node that is coupled to a gate electrode of the second transistor, a third transistor coupled between a fourth input terminal and the first node, and having a gate electrode coupled to a first input terminal, a fourth transistor coupled between the first power source and the second node, and having a gate electrode coupled to the first node, a first controller coupled to the first input terminal and a second input terminal to supply a sampling signal to a second output terminal, a second controller coupled to the first input terminal and a third input terminal to control the voltage of the second node, and a first capacitor coupled between the second input terminal and the second node. 
         [0014]    The emission control line driver may further include a second capacitor coupled between the first node and the first power source. The first input terminal may be configured to receive a first clock signal. The second input terminal may be configured to receive a second clock signal. The third input terminal may be configured to receive a third clock signal. The fourth input terminal may be configured to receive a start signal or a sampling signal of a previous stage. The first clock signal, the second clock signal, and the third clock signal may not overlap each other. Each of the first clock signal and the second clock signal may be set in a period of i (i is a natural number) horizontal periods. The third clock signal may be set in a period of i/2 horizontal periods. The third clock signal may be supplied in a horizontal period after the first clock signal or the second clock signal is supplied in the horizontal period. 
         [0015]    The first controller may include a fifth transistor coupled between the fourth input terminal and a third node, and having a gate electrode coupled to the first input terminal, a sixth transistor coupled between a sixth node and the second input terminal, and having a gate electrode coupled to the third node, a seventh transistor coupled between the sixth node and the first power source, and having a gate electrode coupled to the first output terminal, a third capacitor coupled between the third node and the sixth node, and a fourth capacitor coupled between the first output terminal and the first power source. The second output terminal may be electrically coupled to the sixth node. 
         [0016]    The second controller may include an eighth transistor coupled between the first input terminal and a fourth node, and having a gate electrode coupled to the first node, a ninth transistor coupled between the fourth node and the second power source, and having a gate electrode coupled to the first input terminal, a tenth transistor coupled between the second node and a fifth node, and having a gate electrode coupled to the third input terminal, an eleventh transistor coupled between the fifth node and the third input terminal, and having a gate electrode coupled to the fourth node, and a fifth capacitor coupled between the fourth node and the fifth node. 
         [0017]    The emission control line driver may further include a twelfth transistor coupled between the fourth input terminal and the third transistor, the twelfth transistor being configured to be turned on when a first control signal is supplied to a gate electrode of the twelfth transistor, and a thirteenth transistor coupled between a fifth input terminal and the first controller, the thirteenth transistor being configured to be turned on when a second control signal is supplied to a gate electrode of the thirteenth transistor. The first control signal and the second control signal may not overlap each other. The emission control line driver may further include a fourteenth transistor coupled between the first node and the second power source, the fourteenth transistor being configured to be turned on when a reset signal is supplied to a gate electrode of the fourteenth transistor. The reset signal may be commonly supplied to all of the stages. 
         [0018]    According to an embodiment, an organic light emitting display includes a scan driver for sequentially supplying scan signals to scan lines, a data driver for supplying data signals to data lines, an emission control line driver for supplying emission control signals to emission control lines, and pixels positioned at crossing regions of the scan lines, the data lines, and the emission control lines. The emission control line driver includes stages respectively coupled to the emission control lines. Each of the stages includes a first transistor coupled between a first output terminal and a first power source, the first transistor being configured to be turned on or off to correspond to a voltage applied to a first node that is coupled to a gate electrode of the first transistor, a second transistor coupled between the first output terminal and a second power source that outputs a voltage that is lower than the first power source, the second transistor being configured to be turned on or off to correspond to a voltage applied to a second node that is coupled to a gate electrode of the second transistor, a third transistor coupled between a fourth input terminal and the first node, and having a gate electrode coupled to a first input terminal, a fourth transistor coupled between the first power source and the second node, and having a gate electrode coupled to the first node, a first controller coupled to the first input terminal and a second input terminal to supply a sampling signal to a second output terminal, a second controller coupled to the first input terminal and a third input terminal to control the voltage of the second node, and a first capacitor coupled between the second input terminal and the second node. 
         [0019]    According to the emission control line driver illustrated in the embodiments of the present invention and the organic light emitting display using the same, the voltage of the gate electrode of the transistor that outputs the low signal is periodically reduced using the clock signal so that the stability of an output may be secured. In addition, according to the embodiments of the present invention, the width of the emission control signal may be controlled to correspond to the width of the start signal. Furthermore, according to the embodiments of the present invention, since the stages receive three clock signals, a circuit structure may be simplified. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present invention, and, together with the description, serve to explain the principles of the present invention. 
           [0021]      FIG. 1  is a block diagram illustrating an organic light emitting display according to an embodiment of the present invention; 
           [0022]      FIG. 2  is a block diagram schematically illustrating stages of an emission control line driver of  FIG. 1 ; 
           [0023]      FIG. 3  is a circuit diagram illustrating a first embodiment of one of the stages of  FIG. 2 ; 
           [0024]      FIG. 4  is a waveform chart illustrating the operation processes of one of the stages of  FIG. 3 ; 
           [0025]      FIG. 5  is a circuit diagram illustrating a second embodiment of one of the stages of  FIG. 2 ; and 
           [0026]      FIG. 6  is a circuit diagram illustrating a third embodiment of one of the stages of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Hereinafter, certain exemplary embodiments according to the present invention will be described with reference to the accompanying drawings. Here, when a first element is described as being coupled to a second element, the first element may be directly coupled to the second element or may be indirectly coupled to the second element via one or more third elements. Further, some of the elements that are not essential to the complete understanding of the invention are omitted for clarity. Also, like reference numerals refer to like elements throughout. 
         [0028]    Hereinafter, exemplary embodiments of the present invention, by which those skilled in the art may perform the present invention, will be described in detail with reference to  FIGS. 1 to 6 . 
         [0029]      FIG. 1  is a block diagram illustrating an organic light emitting display according to an embodiment of the present invention. 
         [0030]    Referring to  FIG. 1 , the organic light emitting display according to an embodiment of the present invention includes a display unit  40  that includes pixels  50  positioned at the crossing regions of scan lines S 1  to Sn, data lines D 1  to Dm, and emission control lines E 1  to En, a scan driver  10  for driving the scan lines S 1  to Sn, a data driver  20  for driving the data lines D 1  to Dm, an emission control line driver  30  for driving the emission control lines E 1  to En, and a timing controller  60  for controlling the drivers  10 ,  20 , and  30 . 
         [0031]    The scan driver  10  sequentially supplies scan signals to the scan lines S 1  to Sn. When the scan signals are supplied to the scan lines S 1  to Sn, the pixels  50  are selected in units of horizontal lines (e.g., line-by-line). 
         [0032]    The data driver  20  supplies data signals to the data lines D 1  to Dm in synchronization with the scan signals. The data signals supplied to the data lines D 1  to Dm are supplied to the pixels  50  that are selected by the scan signals. 
         [0033]    The emission control line driver  30  sequentially supplies emission control signals to the emission control lines E 1  to En. Here, the emission control line driver  30  supplies the emission control signals so that the pixels  50  are set in a non-emission state during a period when the voltages corresponding to the data signals are charged. Therefore, the emission control signal supplied to the i th  (i is a natural number) emission control line E i  overlaps the scan signal supplied to the i th  scan line S i . On the other hand, the width of the emission control signal may be suitably set to correspond to the structure of the pixel  50  and the brightness to be realized. 
         [0034]      FIG. 2  is a block diagram schematically illustrating stages of the emission control line driver of  FIG. 1 . 
         [0035]    Referring to  FIG. 2 , the emission control line driver  30  according to an embodiment of the present invention includes n stages  321  to  32   n  in order to supply emission control signals to the n emission control lines E 1  to En. The stages  321  to  32   n  are coupled to the emission control lines E 1  to En, respectively, and are driven by three clock signals CLK 1 , CLK 2 , and CLK 3 . 
         [0036]    Each of the stages  321  to  32   n  includes a first input terminal  33 , a second input terminal  34 , a third input terminal  35 , and a fourth input terminal  36 . 
         [0037]    The first input terminal  33  of a k th  (k is an odd or even number) stage  32   k  receives the first clock signal CLK 1  and the second input terminal  34  receives the second clock signal CLK 2 . The first input terminal  33  of a (k+1) th  stage  32   k +1 receives the second clock signal CLK 2 , and the second input terminal  34  receives the first clock signal CLK 1 . The third clock signal CLK 3  is supplied to the third input terminal  35  of each of the stages  321  to  32   n , and a start signal FLM or a sampling signal of a previous stage is supplied to the fourth input terminal  36 . 
         [0038]    The stages  321  to  32   n  may be formed of the same circuit and generate the emission control signals having width that is changed to correspond to the start signal FLM. 
         [0039]      FIG. 3  is a circuit diagram illustrating a first embodiment of one of the stages of  FIG. 2 . In  FIG. 3 , for convenience sake, the first stage  321  will be illustrated. 
         [0040]    Referring to  FIG. 3 , the stage  321 , according to the first embodiment of the present invention, includes a first transistor M 1 , a second transistor M 2 , a third transistor M 3 , a fourth transistor M 4 , a first capacitor C 1 , a second capacitor C 2 , a first controller  100 , and a second controller  102 . 
         [0041]    The first transistor M 1  is coupled between a first output terminal  37  and a first power source VDD. The gate electrode of the first transistor M 1  is coupled to a first node N 1 . The first transistor M 1  controls the voltage of the first output terminal  37  to correspond to the voltage applied to the first node N 1 . Here, when the first transistor M 1  is turned on, the first power source VDD (e.g., a high voltage) is supplied to the first output terminal  37 . Since the first output terminal  37  is coupled to the emission control line E 1 , the high voltage supplied to the first output terminal  37  is used as an emission control signal. 
         [0042]    The second transistor M 2  is coupled between the first output terminal  37  and a second power source VSS. The gate electrode of the second transistor M 2  is coupled to a second node N 2 . The second transistor M 2  controls the voltage of the first output terminal  37  to correspond to the voltage applied to the second node N 2 . Here, when the second transistor M 2  is turned on, the second power source VSS (e.g., a low voltage) is supplied to the first output terminal  37 . 
         [0043]    The third transistor M 3  is coupled between the fourth input terminal  36  and the first node N 1 . The gate electrode of the third transistor M 3  is coupled to the first input terminal  33 . The third transistor M 3  is turned on or off to correspond to the first clock signal CLK 1  supplied to the first input terminal  33 . When the third transistor M 3  is turned on, the fourth input terminal  36  and the first node N 1  are electrically coupled to each other. When the start signal FLM (or a previous stage sampling signal) is supplied to the fourth input terminal  36 , the first transistor M 1  is turned on. 
         [0044]    The fourth transistor M 4  is coupled between the first power source VDD and the second node N 2 . The gate electrode of the fourth transistor M 4  is coupled to the first node N 1 . The fourth transistor M 4  is turned on or off to correspond to the voltage that is applied to the first node N 1  in order to control the voltage of the second node N 2 . That is, the fourth transistor M 4  is turned on when a low voltage is applied to the first node N 1  in order to supply the voltage of the first power source VDD to the second node N 2 . When the low voltage is supplied to the first node N 1 , the high voltage of the first power source VDD is supplied to the second node N 2  so that the first transistor M 1  and the second transistor M 2  are turned on or off at different times. 
         [0045]    The first capacitor C 1  is coupled between the second input terminal  34  and the second node N 2 . The first capacitor C 1  controls the voltage of the second node N 2  to correspond to the second clock signal CLK 2  supplied to the second input terminal  34 . The operation processes of the first capacitor C 1  will be described later in more detail. 
         [0046]    The second capacitor C 2  is coupled between the first node N 1  and the first power source VDD. The second capacitor C 2  is charged with the voltage corresponding to the turning on or off of the first transistor M 1 . 
         [0047]    A first controller  100  supplies a sampling signal to a second output terminal  38  to correspond to the first clock signal CLK 1  and the second clock signal CLK 2 . Therefore, the first controller  100  includes a fifth transistor M 5 , a sixth transistor M 6 , a seventh transistor M 7 , a third capacitor C 3 , and a fourth capacitor C 4 . 
         [0048]    The fifth transistor M 5  is coupled between the fourth input terminal  36  and a third node N 3 . The gate electrode of the fifth transistor M 5  is coupled to the first input terminal  33 . The fifth transistor M 5  is turned on or off to correspond to the first clock signal CLK 1  supplied to the first input terminal  33  in order to control the voltage of the third node N 3 . 
         [0049]    The sixth transistor M 6  is coupled between a sixth node N 6  and the second input terminal  34 . The gate electrode of the sixth transistor M 6  is coupled to the third node N 3 . The sixth transistor M 6  controls the voltage of the sixth node N 6  to correspond to the voltage applied to the third node N 3 . 
         [0050]    The seventh transistor M 7  is coupled between the first power source VDD and the sixth node N 6 . The gate electrode of the seventh transistor M 7  is coupled to the first output terminal  37 . The seventh transistor M 7  is turned on or off to correspond to the voltage applied to the first output terminal  37  in order to control the voltage of the sixth node N 6 . 
         [0051]    The third capacitor C 3  is coupled between the third node N 3  and the sixth node N 6 . The third capacitor C 3  is charged with the voltage corresponding to the turning on or turning off of the sixth transistor M 6 . 
         [0052]    The fourth capacitor C 4  is coupled between the first power source VDD and the first output terminal  37 . The fourth capacitor C 4  is charged with the voltage corresponding to the turning on or off of the seventh transistor M 7 . 
         [0053]    In  FIG. 3 , the second output terminal  38  is coupled to the sixth node N 6 . The second output terminal  38  supplies the voltage applied to the sixth node N 6  as a sampling signal to a next stage  322 . 
         [0054]    The second controller  102  controls the voltage of the second node N 2  to correspond to the first clock signal CLK 1  and the third clock signal CLK 3 . Here, in a period when the emission control signal is not supplied to the first output terminal  37 , the second controller  102  maintains the voltage of the second node N 2  as a low voltage. In  FIG. 3 , the second controller  102  includes an eighth transistor M 8 , a ninth transistor M 9 , a tenth transistor M 10 , an eleventh transistor M 11 , and a fifth capacitor C 5 . 
         [0055]    The eighth transistor M 8  is coupled between the first input terminal  33  and a fourth node N 4 . The gate electrode of the eighth transistor M 8  is coupled to the first node N 1 . The eighth transistor M 8  is turned on or off to correspond to the voltage applied to the first node N 1  in order to control the voltage of the fourth node N 4 . 
         [0056]    The ninth transistor M 9  is coupled between the fourth node N 4  and the second power source VSS. The gate electrode of the ninth transistor M 9  is coupled to the first input terminal  33 . The ninth transistor M 9  is turned on or off to correspond to the first clock signal CLK 1  supplied to the first input terminal  33  in order to control the voltage of the fourth node N 4 . 
         [0057]    The tenth transistor M 10  is coupled between the second node N 2  and a fifth node N 5 . The gate electrode of the tenth transistor M 10  is coupled to a third input terminal  35 . The tenth transistor M 10  is turned on or off to correspond to the third clock signal CLK 3  supplied to the third input terminal  35  in order to control the voltage of the second node N 2 . 
         [0058]    The eleventh transistor M 11  is coupled between the fifth node N 5  and the third input terminal  35 . The gate electrode of the eleventh transistor M 11  is coupled to the fourth node N 4 . The eleventh transistor M 11  is turned on or off to correspond to the voltage applied to the fourth node N 4  in order to control the voltage of the fifth node N 5 . 
         [0059]    The fifth capacitor C 5  is coupled between the fourth node N 4  and the fifth node N 5 . The fifth capacitor C 5  is charged with the voltage corresponding to the turning on or off of the eleventh transistor M 11 . 
         [0060]      FIG. 4  is a waveform chart illustrating the operation processes of the stage of  FIG. 3 . 
         [0061]    Referring to  FIG. 4 , the first clock signal CLK 1  and the second clock signal CLK 2  are supplied in the period of iH (i is a natural number, e.g., a horizontal period), and the third clock signal CLK 3  is supplied in the period of i/2H. In  FIG. 4 , for convenience sake, the first clock signal CLK 1  and the second clock signal CLK 2  are set in the period of 2H and the third clock signal CLK 3  is set in the period of 1H. 
         [0062]    In  FIG. 4 , the first clock signal CLK 1  and the second clock signal CLK 2  are supplied in different horizontal periods H, and the third clock signal CLK 3  is supplied every horizontal period H so that the first clock signal CLK 1  does not overlap the third clock signal CLK 3 . Then, in the horizontal period H, after the first clock signal CLK 1  or the second clock signal CLK 2  is supplied, the third clock signal CLK 3  is supplied. That is, in an exemplary horizontal period, the third clock signal CLK 3  is supplied after the first clock signal CLK 1  is supplied. In the next horizontal period, the third clock signal CLK 3  is supplied after the second clock signal CLK 2  is supplied. 
         [0063]    Operation processes will be described in more detail as follows. First, the start signal FLM (e.g., the low signal) is supplied to the fourth input terminal  36 . After the start signal FLM is supplied to the fourth input terminal  36 , the first clock signal CLK 1  is supplied to the first input terminal  33 . When the first clock signal CLK 1  is supplied, the third transistor M 3 , the fifth transistor M 5 , and the ninth transistor M 9  are turned on. 
         [0064]    When the third transistor M 3  is turned on, the start signal FLM is supplied to the first node N 1 . When the start signal FLM is supplied to the first node N 1 , the first transistor M 1 , the fourth transistor M 4 , and the eighth transistor M 8  are turned on. 
         [0065]    When the first transistor M 1  is turned on, the voltage corresponding to the turning on of the first transistor M 1  is charged at the second capacitor C 2 . When the first transistor M 1  is turned on, the voltage of the first power source VDD is supplied to the first output terminal  37 . In this case, the emission control signal is supplied to the emission control line E 1 . 
         [0066]    When the fourth transistor M 4  is turned on, the first power source VDD is supplied to the second node N 2 . When the first power source VDD is supplied to the second node N 2 , the second transistor M 2  is turned off. When the second transistor M 2  is turned off, the first power source VDD may be stably supplied to the first output terminal  37 . 
         [0067]    When the eighth transistor M 8  is turned on, the fourth node N 4  and the first input terminal  33  are electrically coupled to each other. Here, since the first clock signal CLK 1  is supplied to the first input terminal  33 , the fourth node N 4  receives a low voltage. 
         [0068]    When the fifth transistor M 5  is turned on, the start signal is supplied to the third node N 3 . When the start signal is supplied to the third node N 3 , the sixth transistor M 6  is turned on. When the sixth transistor M 6  is turned on, the sixth node N 6  and the second input terminal  34  are electrically coupled to each other. Here, since the second clock signal CLK 2  is not supplied to the second input terminal  34 , the sixth node N 6  maintains a high voltage so that a sampling signal is not supplied to the second output terminal  38 . On the other hand, since the sixth transistor M 6  is turned on, the voltage corresponding to the turning on of the sixth transistor M 6  is charged at the third capacitor C 3 . 
         [0069]    When the ninth transistor M 9  is turned on, the voltage of the second power source VSS is supplied to the fourth node N 4 . When the second power source VSS is supplied to the fourth node N 4 , the eleventh transistor M 11  is turned on. When the eleventh transistor M 11  is turned on, the fifth node N 5  and the third input terminal  35  are electrically coupled to each other. Here, since the third clock signal CLK 3  is not supplied to the third input terminal  35 , the fifth node N 5  maintains a high voltage. On the other hand, since the eleventh transistor M 11  is turned on, the voltage corresponding to the turning on of the eleventh transistor is charged at the fifth capacitor C 5 . 
         [0070]    Then, the supply of the first clock signal CLK 1  to the first input terminal  33  is stopped. When the supply of the first clock signal CLK 1  is stopped, the third transistor M 3 , the fifth transistor M 5 , and the ninth transistor M 9  are turned off. 
         [0071]    When the third transistor M 3  is turned off, the fourth input terminal  36  and the first node N 1  are electrically isolated from each other. Here, the first node N 1  maintains a low voltage by the second capacitor C 2 . Therefore, the first transistor M 1  maintains a turn on state so that the voltage of the first power source VDD is output to the first output terminal  37 . Since the fourth transistor M 4  maintains a turn on state by the voltage of the second capacitor C 2 , the second transistor M 2  stably maintains a turn off state. 
         [0072]    When the fifth transistor M 5  is turned off, the fourth input terminal  36  and the third node N 3  are electrically isolated from each other. Here, the sixth transistor M 6  maintains a turn on state to correspond to the voltage charged at the third capacitor C 3  so that the second output terminal  38  maintains a previous voltage. 
         [0073]    When the ninth transistor M 9  is turned off, the fourth node N 4  and the second power source VSS are electrically isolated from each other. Here, since the eighth transistor M 8  maintains a turned on state to correspond to the voltage applied to the first node N 1 , the fourth node N 4  and the first input terminal  33  are electrically coupled to each other. Therefore, the voltage of the fourth node N 4  increases to the voltage supplied to the first input terminal  33  (e.g., the voltage of a high signal). When the fourth node N 4  receives the voltage of the high signal, the eleventh transistor M 11  is turned off. Here, the fifth capacitor C 5  is charged with the voltage corresponding to the turning off of the eleventh transistor M 11 . 
         [0074]    Then, the third clock signal CLK 3  is supplied to the third input terminal  35 . When the third clock signal CLK 3  is supplied, the tenth transistor M 10  is turned on. When the tenth transistor M 10  is turned on, the second node N 2  and the fifth node N 5  are electrically coupled to each other. At this time, since the fourth transistor M 4  maintains a turned on state and the eleventh transistor M 11  maintains a turned off state, the second node N 2  maintains the voltage of the first power source VDD. 
         [0075]    After the third clock signal CLK 3  is supplied, the second clock signal CLK 2  is supplied to the second input terminal  34  in the next horizontal period. Here, since the sixth transistor M 6  is set in a turn on state, the second clock signal CLK 2  is supplied to the sixth node N 6 . The second clock signal CLK 2  supplied to the sixth node N 6  as a sampling signal is supplied to the next stage via the second output terminal  38 . On the other hand, when the second clock signal CLK 2  is supplied to the sixth node N 6 , the voltage of the third node N 3  is reduced by the coupling of the third capacitor C 3 . Therefore, the sixth transistor M 6  stably maintains a turned on state. 
         [0076]    Additionally, the second clock signal CLK 2  supplied to the second input terminal  34  is transmitted to the second node N 2  by the coupling of the first capacitor C 1 . Here, since the second node N 2  receives the first power source VDD, the voltage of the first power source VDD is maintained without a change in a voltage. 
         [0077]    Then, the third clock signal CLK 3  is supplied to the third input terminal  35 . When the third clock signal CLK 3  is supplied, the tenth transistor M 10  is turned on. When the tenth transistor M 10  is turned on, the second node N 2  and the fifth node N 5  are electrically coupled to each other. Here, since the fourth transistor M 4  maintains a turned on state and the eleventh transistor M 11  maintains a turned off state, the second node N 2  maintains the voltage of the first power source VDD. 
         [0078]    After the third clock signal CLK 3  is supplied, the supply of the start signal FLM is stopped (e.g., a high voltage) in the next horizontal period, and the first clock signal CLK 1  is supplied to the first input terminal  33 . 
         [0079]    When the first clock signal CLK 1  is supplied, the third transistor M 3 , the fifth transistor M 5 , and the ninth transistor M 9  are turned on. 
         [0080]    When the third transistor M 3  is turned on, the first node N 1  and the fourth input terminal  36  are electrically coupled to each other. Here, since a high voltage is supplied to the first node N 1 , the first transistor M 1 , the fourth transistor M 4 , and the eighth transistor M 8  are turned off. When the first transistor M 1  is turned off, the first output terminal  37  is set in a floating state. In this case, the first output terminal  37  maintains the high voltage that is an output signal of a previous period. 
         [0081]    Since the emission control signal supplied to the emission control line E 1  is supplied to the pixels  50 , charging is performed by the capacitors of the pixels. Therefore, although the first output terminal  37  is set in a floating state, the output voltage of a previous period is maintained by the parasitic capacitors of the pixels  50  and the emission control line. 
         [0082]    When the fifth transistor M 5  is turned on, a high voltage is supplied to the third node N 3  so that the sixth transistor M 6  is turned off. When the sixth transistor M 6  is turned off, the sixth node N 6  and the second input terminal  34  are electrically isolated from each other. Here, the third capacitor C 3  is charged with the voltage corresponding to the turning off of the sixth transistor M 6 . 
         [0083]    When the ninth transistor M 9  is turned on, the fourth node N 4  and the second power source VSS are electrically coupled to each other. Here, the fourth node N 4  receives the voltage of the second power source VSS so that the eleventh transistor M 11  is turned on. When the eleventh transistor M 1  is turned on, the fifth node N 5  and the third input terminal  35  are electrically coupled to each other. On the other hand, the voltage corresponding to the turning on of the eleventh transistor M 11  is stored at the fifth capacitor C 5 . 
         [0084]    Then, the third clock signal CLK 3  is supplied to the third input terminal  35 . When the third clock signal CLK 3  is supplied, the tenth transistor M 10  is turned on. When the tenth transistor M 10  is turned on, the second node N 2  and the third input terminal  35  are electrically coupled to each other via the fifth node N 5 . Here, the third clock signal CLK 3  (e.g., a low voltage) is supplied to the second node N 2 . When the low voltage is supplied to the second node N 2 , the second transistor M 2  is turned on so that the voltage of the second power source VSS is output to the first output terminal  37 . In this case, the supply of the emission control signal to the emission control line E 1  is stopped. When the second power source VSS is supplied to the first output terminal  37 , the seventh transistor M 7  is turned on. When the seventh transistor M 7  is turned on, the voltage of the first power source VDD is supplied to the sixth node N 6 . 
         [0085]    According to an embodiment of the present invention, the third clock signal CLK 3  may be set as a voltage lower than the second power source VSS so that the second transistor M 2  may be stably turned on. Then, the stage  321  outputs the voltage of the first power source VDD to the first output terminal  37  until the next start signal FLM is supplied. 
         [0086]    Additionally, according to embodiments of the present invention, whenever the second clock signal CLK 2  is supplied, the voltage of the second node N 2  is reduced by the coupling of the first capacitor C 1 . Therefore, the voltage of the second node N 2  stably maintains a low voltage so that the voltage of the second power source VSS may be stably output to the first output terminal  37 . 
         [0087]    On the other hand, a sampling signal is supplied to the next stage in synchronization with the second clock signal CLK 2  (In the next stage, the second clock signal CLK 2  is supplied to the first input terminal). In this case, the next stage stably outputs the emission control signal using the sampling signal. 
         [0088]    Additionally, in  FIG. 4 , it is illustrated that one sampling signal is generated to correspond to the start signal FLM. However, the present invention is not limited to the above. For example, when the start signal FLM overlaps two first clock signals CLK 1 , two sampling signals are supplied to the next stage. Therefore, according to embodiments of the present invention, the width of the start signal FLM is controlled so that the width of the emission control signal may be freely controlled. 
         [0089]      FIG. 5  is a circuit diagram illustrating a second embodiment of the stage of  FIG. 2 . In  FIG. 5 , the same elements as those of  FIG. 3  are denoted by the same reference numerals and detailed description thereof will be omitted. 
         [0090]    Referring to  FIG. 5 , the stage  321 , according to the second embodiment of the present invention, further includes a twelfth transistor M 12  and a thirteenth transistor M 13  for bidirectional driving. 
         [0091]    The twelfth transistor M 12  is coupled between the fourth input terminal  36  and the third transistor M 3 . The gate electrode of the twelfth transistor M 12  receives a first control signal CS 1 . The twelfth transistor M 12  is turned on when the first control signal CS 1  is supplied. 
         [0092]    The thirteenth transistor M 13  is coupled between a fifth input terminal  39  and the fifth transistor M 5  (or a first controller  100 ). Then, the gate electrode of the thirteenth transistor M 13  receives a second control signal CS 2 . The thirteenth transistor M 13  is turned on when the second control signal CS 2  is supplied. The fifth input terminal  39  receives the start signal or the sampling signal of the next stage. 
         [0093]    Here, the first control signal CS 1  and the second control signal CS 2  are supplied at different times (e.g., not overlapped with each other). For example, when the emission control signals are supplied in a first direction (from top to bottom of a panel), the first control signal CS 1  is supplied so that the twelfth transistor M 12  is turned on and so that the thirteenth transistor M 13  maintains a turned off state. When the emission control signals are supplied in a second direction (from bottom to top of the panel), the second control signal CS 2  is supplied so that the thirteenth transistor M 13  is turned on and so that the twelfth transistor M 12  maintains a turned off state. 
         [0094]    The stage  321 , according to the second embodiment of the present invention, further includes the twelfth transistor M 12  and the thirteenth transistor M 13  for bidirectional driving, and the operation processes are substantially the same as the first embodiment illustrated in  FIG. 3 . 
         [0095]      FIG. 6  is a circuit diagram illustrating a third embodiment of the stage of  FIG. 2 . In  FIG. 6 , the same elements as those of  FIG. 3  are denoted by the same reference numerals, and detailed description thereof will be omitted. 
         [0096]    Referring to  FIG. 6 , the stage  321 , according to the third embodiment of the present invention, further includes a fourteenth transistor M 14  coupled between the first node N 1  and the second power source VSS. The fourteenth transistor M 14  is turned on to supply the voltage of the second power source VSS to the first node N 1  when a reset signal (Reset) is supplied to the gate of the fourteenth transistor M 14 . When the second power source VSS is supplied to the first node N 1 , the first transistor M 1  is turned on so that the voltage of the first power source VDD is supplied to the first output terminal  37 . 
         [0097]    Here, the reset signal (Reset) is commonly supplied to all of the stages  321  to  32   n  when a power source is turned on and/or off. As described above, when the reset signal (Reset) is supplied and the power source is turned on and/or off, the emission control signals are supplied to the emission control lines E 1  to En so that the pixels  50  are set in a non-emission state. That is, according to the third embodiment of the present invention, it is possible to prevent over-current from flowing or unnecessary light from being generated when the power source is turned on and/or off using the reset signal. 
         [0098]    Additionally, in  FIG. 2 , the third clock signal CLK 3  is supplied to all of the stages  321  to  32   n . However, the present invention is not limited to the above. For example, the third clock signal CLK 3  may be supplied to even and odd stages via different lines. Then, the load of the third clock signal CLK 3  is minimized or reduced so that the stability of driving the stages may be improved. 
         [0099]    The present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.