KR100570782B1 - Light emitting display - Google Patents

Abstract

The present invention provides a light emitting display device capable of reducing the effect of kickback caused by parasitic capacitance present in a pixel circuit.

The pixel circuit of the light emitting display device according to the present invention may include first and second transistors turned on in response to a first control signal and connected in series with each other, and first and second transistors connected in series with each other. A first capacitor, a third transistor for applying a data voltage to the first electrode of the first capacitor in response to the selection signal, a fourth transistor for outputting a current corresponding to a gate-source voltage depending on the voltage of the first capacitor, and a fourth transistor It includes a light emitting element that emits light corresponding to the current from the transistor. The first electrode of the first transistor is connected to the first electrode of the first capacitor, the second electrode of the first transistor is connected to the first electrode of the second transistor, and the second electrode of the second transistor is the first capacitor. It may be connected to the second electrode of the.

OLED, light emitting display device, pixel circuit, parasitic capacitance

Description

Light emitting display device

FIG. 1 is an equivalent circuit diagram of a conventional pixel, and equivalently shows one pixel of N × M pixels.

2 is a diagram schematically illustrating a configuration of an organic light emitting display device according to a first embodiment of the present invention.

3 is an equivalent circuit diagram illustrating a pixel circuit 110 according to a first embodiment of the present invention.

4 is a diagram illustrating a signal waveform applied to the recovery circuit 110.

5 is an equivalent circuit diagram illustrating a pixel circuit 120 according to a second embodiment of the present invention.

6 is an equivalent circuit diagram illustrating a pixel circuit 130 according to a third embodiment of the present invention.

The present invention relates to a light emitting display device, and more particularly, to an organic light emitting display device using light emission of an organic material.

In general, an organic light emitting display device is a display device using an organic light emitting device using light emission of an organic material. An organic light emitting display device displays an image by voltage driving or current driving N × M organic light emitting cells arranged in a matrix.

Such an organic light emitting cell has a diode characteristic and is also called an organic light emitting diode (hereinafter, referred to as an organic light emitting diode), and has a structure of an anode (ITO), an organic thin film, and a cathode electrode layer (metal). The organic thin film has a multilayer structure including an emitting layer (EML), an electron transport layer (ETL), and a hole transport layer (HTL) to improve the emission efficiency by improving the balance between electrons and holes. It also includes a separate electron injecting layer (EIL) and a hole injecting layer (HIL). These organic light emitting cells are arranged in an N × M matrix to form an organic EL display panel.

The organic light emitting cell may be driven using a simple matrix method and an active matrix method using a thin film transistor (TFT) or a MOSFET. In the simple matrix method, the anode and the cathode are orthogonal and the line is selected and driven, whereas the active driving method connects a thin film transistor to each indium tin oxide (ITO) pixel electrode and is maintained by a capacitor capacitance connected to the gate of the thin film transistor. It is driven according to the voltage.

Hereinafter, a pixel of a conventional active driving organic light emitting display device will be described.

FIG. 1 is an equivalent circuit diagram of a conventional pixel, and equivalently shows one pixel of N × M pixels.

As shown in FIG. 1, the pixel circuit includes an organic light emitting diode OLED, two transistors SM and DM, and a capacitor Cst. The two transistors SM and DM may be formed as PMOS transistors.

When the switching transistor SM is turned on in response to the selection signal applied to the gate, the data voltage V _DATA from the data line Dm is applied to the gate of the transistor DM. Then, corresponding to the voltage (V _GS) charged between the gate and the source to the flowing current (I _OLED) to the transistor (DM), in response to the current (I _OLED) organic light-emitting device (OLED) by the capacitor (Cst) Emits light. In this case, the current I _OLED flowing through the organic light emitting diode _OLED is represented by Equation 1 below.

In the pixel shown in FIG. 1, a current corresponding to the data voltage is supplied to the OLED, and the OLED emits light at a luminance corresponding to the supplied current. In this case, the applied data voltage has a multi-level value in a predetermined range in order to express a predetermined gray level.

However, as can be seen from Equation 1, in the pixel circuit, the value of the current I _OLED varies depending on the threshold voltage Vth of the driving transistor DM. Therefore, the threshold voltage Vth of the transistor DM may be different for each pixel, which makes it difficult to accurately display an image.

An object of the present invention is to provide a light emitting display device including a pixel circuit capable of compensating a threshold voltage of a driving transistor.

Another object of the present invention is to provide a light emitting display device capable of reducing the influence of kickback caused by parasitic capacitance present in a pixel circuit.

As a means for achieving the above object, the light emitting display device according to the present invention, a plurality of data lines for transmitting a data voltage, a plurality of scan lines for transmitting a selection signal, and a plurality of pixels electrically connected to the scan line and the data line A light emitting display device comprising a circuit,

The pixel circuit,

First and second transistors each turned on in response to the first control signal and connected in series with each other;

A first capacitor connected in parallel with the first and second transistors connected in series;

A third transistor applying the data voltage to the first electrode of the first capacitor in response to the selection signal;

A fourth transistor outputting a current corresponding to a gate-source voltage depending on the voltage of the first capacitor; And

And a light emitting device that emits light corresponding to the current from the fourth transistor.

The first electrode of the first transistor is connected to the first electrode of the first capacitor, the second electrode of the first transistor is connected to the first electrode of the second transistor, and the second electrode of the second transistor is It may be connected to the second electrode of the first capacitor.

A double gate transistor may be formed by the first and second transistors.

The first and second transistors may have different sizes.

The channel length of the second transistor may be longer than the channel length of the first transistor.

The pixel circuit may include a second capacitor connected between the first electrode of the first capacitor and the gate of the fourth transistor; And a first switch connecting the fourth transistor in the form of a diode in response to the first control signal, wherein a gate of the fourth transistor is connected to a second electrode of a second capacitor, A source may be connected to the second electrode of the first capacitor to output the current.

The first switch may further include fifth and sixth transistors turned on in response to the first control signal and connected in series, and a double gate transistor may be formed by the fifth and sixth transistors.

And a second switch configured to transfer a current output from the fourth transistor to the light emitting device in response to a second control signal, wherein the second control signal may be applied after the first control signal and the selection signal. have.

The first control signal may be a previous selection signal applied before the selection signal.

The light emitting device may be a device using light emission of an organic material.

According to another aspect of the present invention, a light emitting display device includes a plurality of data lines for transmitting a data voltage, a plurality of scan lines for respectively transmitting selection signals including first and second selection signals, and a plurality of scan lines and a plurality of scan lines and data lines. A light emitting display device comprising a plurality of pixel circuits connected to each other.

The pixel circuit,

A first transistor having a first main electrode connected to the data line and a second main electrode turned on in response to the second selection signal to transfer the data voltage;

A first capacitor storing a voltage corresponding to the data voltage transferred by the first transistor;

Second and third transistors connected in series with each other and turned on in response to the first selection signal to be connected in parallel with the first capacitor;

A fourth transistor for outputting a current corresponding to the voltage stored in the first capacitor;

Fifth and sixth transistors connected in series with each other and turned on in response to the first selection signal to connect the first transistor in the form of a diode;

A second capacitor connected to a first electrode of the first capacitor and the fourth transistor between a control electrode to store a voltage corresponding to the threshold voltage of the fourth transistor; And

It includes a light emitting device for emitting light corresponding to the current output from the fourth transistor.

The second and third transistors may have different sizes.

One transistor of the second and third transistors electrically contacting the second main electrode of the first transistor may have a shorter channel length than the other transistor.

The fifth and sixth transistors may have different sizes.

Among the fifth and sixth transistors, one transistor electrically contacting the control electrode of the fourth transistor may have a shorter channel length than the other transistor.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

2 is a diagram schematically illustrating a configuration of an organic light emitting display device according to a first embodiment of the present invention.

As shown in FIG. 2, the organic light emitting display device includes an organic light emitting display panel 100, a scan driver 200, a data driver 300, and a light emission control signal driver 400.

The organic light emitting display panel 100 includes a plurality of data lines D1 -Dm extending in a column direction, a plurality of scanning lines S1 -Sn extending in a row direction, a plurality of emission control lines E1 to Tu, and a plurality of data lines. The pixel circuit 110 is included. The data lines D1 -Dm transmit a data signal representing an image signal to the pixel circuit 110, and the scan lines S1 -Sn transfer a selection signal to the pixel circuit 110.

The scan driver 200 sequentially generates and applies selection signals to the scan lines S1 -Sn, and when defining terms relating to the scan lines, the scan line to which the current selection signal is to be transmitted is referred to as a "current scan line". The scanning line which transmitted the selection signal immediately before the selection signal is transmitted is referred to as the "previous scanning line". The data driver 300 generates and applies a data voltage corresponding to the image signal to the data lines D1 -Dm. The light emitting scan driver 300 sequentially applies a light emitting signal for controlling light emission of the organic light emitting diode to the light emitting scan lines E1 to En.

The scan driver 200, the data driver 300, and / or the emission control signal driver 400 may be electrically connected to the display panel 100, or may be attached to the display panel 100 and electrically connected to the tape carrier package. (tape carrier package, TCP) may be mounted in the form of a chip. Alternatively, the display panel 100 may be mounted in a flexible printed circuit (FPC) or a film that is adhered to and electrically connected to the display panel 100 in the form of a chip. Alternatively, the scan driver 200, the data driver 300, and / or the emission control signal driver 400 may be directly mounted on the glass substrate of the display panel, or may have the same layers as the scan line, the data line, and the thin film transistor on the glass substrate. It may be replaced with or directly mounted to the driving circuit formed with a.

3 is an equivalent circuit diagram illustrating a pixel circuit 110 according to a first embodiment of the present invention.

As shown in FIG. 3, the pixel circuit 110 includes five transistors M1-M5, two capacitors Cst and Cvth, and an organic light emitting diode OLED. The five transistors M1-M5 may be formed as PMOS transistors.

The transistor M1 is a driving transistor for driving the organic light emitting diode OLED. The transistor M1 is connected between a power supply for supplying the voltage VDD and the organic light emitting diode OLED. The transistor M5 is applied by a voltage applied to the gate. The current flowing through the OLED is controlled through the OLED. The transistor M3 diode-connects the transistor M1 in response to a selection signal from the immediately preceding scan line Sn-1. One electrode A of the capacitor Cvth is connected to the gate of the transistor M1, and the capacitor Cst and the transistor M4 are connected between the other electrode B of the capacitor Cvth and a power supply for supplying the voltage VDD. Are connected in parallel. The transistor M4 supplies the power supply VDD to the other electrode B of the capacitor Cvth in response to the selection signal from the immediately preceding scan line Sn-1. In the first embodiment, the transistor M4 is connected to the voltage VDD, but may be connected to a power source voltage different from the voltage VDD.

The transistor M5 transmits the data signal transmitted from the data line Dm to the other electrode B of the capacitor Cvth in response to the selection signal from the current scan line Sn. The transistor M2 is connected between the drain of the transistor M1 and the anode of the organic light emitting element OLED, and in response to the selection signal from the immediately preceding scan line Sn-1, the drain of the transistor M1 and the organic light emitting element OLED. ). The organic light emitting diode OLED emits light corresponding to a current input from the transistor M1 through the transistor M2.

Next, the operation of the pixel circuit 110 will be described with reference to FIG. 4. 4 is a diagram illustrating a signal waveform applied to the recovery circuit 110.

First, when a low level scan voltage is applied to the immediately preceding scan line Sn- 1 during the time D1, the transistor M3 is turned on so that the transistor M1 is in a diode-connected state. Accordingly, the voltage between the gate and the source of the transistor M1 changes until the threshold voltage Vth of the transistor M1 becomes. At this time, since the source of the transistor M1 is connected to the power supply VDD, the voltage applied to the gate of the transistor M1, that is, the node A of the capacitor Cvth, is the power supply voltage VDD and the threshold voltage Vth. Is the sum of. In addition, since the transistor M4 is turned on and the power supply VDD is applied to the node B of the capacitor Cvth, the voltage V _CVth charged in the capacitor Cvth is _expressed by Equation 2 below.

Here, VCvth means a voltage charged in the capacitor (Cvth), V _CvthA is a voltage applied to the node (A) of the capacitor (Cvth), V _CvthB is a voltage applied to the node (B) of the capacitor (Cvth) Means.

While the voltage is charged to the capacitor Cvth, the transistor M2 is turned off because a high level signal is applied to the emission control line En. Therefore, the current flowing through the transistor M1 is prevented from flowing to the organic light emitting element OLED. In addition, since a high level signal is applied to the current scan line Sn, the transistor M5 is also turned off.

Next, during a time D2, when a low level scan voltage is applied to the current scan line Sn, the transistor M5 is turned on to apply the data voltage Vdata to the node B. In addition, since the capacitor Cvth is charged with a voltage corresponding to the threshold voltage Vth of the transistor M1, the gate of the transistor M1 is charged with the data voltage Vdata and the threshold voltage Vth of the transistor M1. The voltage corresponding to the sum is applied. That is, the gate-source voltage Vgs of the transistor M1 is expressed by Equation 3 below. At this time, a high level signal is applied to the emission control line En, and the transistor M2 is turned off.

Then, during the time D3, the transistor M2 is turned on in response to the low level light emission control signal of the light emission control line En, so that the current corresponding to the gate-source voltage V _GS of the transistor M1 ( I _OLED ) is supplied to the OLED, and the OLED emits light. The current I _{OLED is} shown in Equation 4.

Here, the current I _OLED is a current flowing through the OLED, Vgs is a voltage between the source and the gate of the transistor M1, Vth is a threshold voltage of the transistor M1, Vdata is a data voltage, and β is a constant. Indicates a value. As can be seen from Equation 4, since the current I _OLED is determined according to the data voltage Vdata and the power supply VDD regardless of the threshold voltage of the driving transistor, the display panel can be driven stably.

The signal waveform shown in FIG. 4 is one example of a waveform that may be applied to the pixel circuit 110, and is not limited thereto. For example, the start point at which the high level signal applied to the emission control line En is applied during the time periods D1 and D2 may be applied later than the start point of the low level selection signal applied to the straight scan line Sn-1. It may be applied later than the end point of the low level selection signal applied to the current scan line Sn.

However, as described above, the transistors M3 and M4 are turned off after the low level previous selection signal from the previous scan line Sn-1 is applied, and the low current selection signal is applied from the scan line Sn. When the transistor M5 is turned on, the data voltage is applied to the node B, which is one end of the capacitor Cst. Therefore, when the driving transistor M1 is turned on, a voltage corresponding to the data voltage is stored in the capacitor Cst. As a result of the voltage stored in the capacitor Cst, the voltage between the source and the gate of the driving transistor M1 is maintained even when the switching transistor M5 is turned off and the data voltage is not applied to the node B.

However, due to the parasitic capacitance present in the node B, the voltage transferred to the node B is shifted by a predetermined amount ΔV from the data voltage V _data , thereby shifting the voltage to the node B. (Voltage Shift) is generated. At this time, the shift of the predetermined amount of voltage is called kickback, and the shifted voltage change amount ΔV is called kickback voltage. Such kickback may deteriorate the display characteristics of the panel, such as afterimages on the display image. In particular, when the magnitude of the kickback voltage is larger than the gradation level interval, the kickback voltage may be displayed differently to be distinguishable even though the gradation level is the same gradation, thereby greatly reducing the display quality.

Hereinafter, the second and third embodiments of the present invention for solving the effects of the kickback described above will be described in detail.

5 is an equivalent circuit diagram illustrating a pixel circuit 120 according to a second embodiment of the present invention. The pixel circuit 120 according to the second embodiment of the present invention differs from the first embodiment in that the dual transistors M4_1 and M4_2 are used to reduce the kickback voltage of the node B. FIG.

The pixel circuit 120 includes six transistors M1, M2, M3, M4_1, M4_2, and M5, two capacitors Cst and Cvth, and an organic light emitting diode OLED. The pixel circuit 120 includes four transistors M1, M2, M3 and M5, two capacitors Cst and Cvth and an organic light emitting diode OLED, except for the transistors M4_1 and M4_2. It is the same as the circuit 110 and the operation thereof is also the same, so a detailed description thereof will be omitted.

On the other hand, the transistor M4_2 has a source connected to the power supply VDD and a drain connected to the source of the transistor M4_1. The drain of the transistor M4_1 is connected to the drain of the transistor M5. That is, the two transistors M4_1 and M4_2 form a double transistor connected in series with each other. In addition, the gates of both transistors M4_1 and M4_2 are directly connected to the scan line Sn-1. Therefore, in response to the previous selection signal, both transistors M4_1 and M4_2 are simultaneously turned on to apply the power supply voltage VDD to one end of the capacitor Cst.

As shown in FIG. 5, by using the double transistors M4_1 and M4_2, the transistors M4_1 and M4_2 are turned off by the signal of the previous scan line Sn−1, and the transistors (B) are turned on by the signal of the current scan line Sn. When M5) is turned on and a data voltage is applied to the node B between the capacitor Cst and the capacitor Cvth, the kickback voltage at the node B can be reduced. Accordingly, the kickback voltage of the node B is reduced, so that the amount of change in the data voltage applied to the node B is reduced and the voltage variation of the gate node A of the transistor M1 is reduced. Therefore, the voltage Vgs between the gate and the source of the transistor M1 may be significantly reduced by the kickback voltage, thereby significantly reducing the effect on the kickback of the current I _OLED delivered to the organic light emitting diode.

Here, when the total size of the double transistors M4_1 and M4_2, that is, the total channel length L, is constant, a larger channel length of the transistor M4_2 than the channel length of the transistor M4_1 may reduce the kickback voltage more effectively. have.

Table 1 shows that when the channel width W of each of the double transistors M4_1 and M4_2 is 5 μm, and the total channel length L of the two transistors is 20 μm, the channel lengths of the transistors M4_1 and M4_2 are shown. As a result, the voltages of the node B when the double transistors M4_1 and M4_2 are turned on and the voltage of the node B when the transistors are turned off are shown.

Size of transistor Node (B) voltage Kickback voltage M4_1 (W / L) M4_2 (W / L) On turn On turn off 5 / 15㎛ 5 / 5㎛ 5.0 5.4917 V 0.4916V 5 / 10㎛ 5 / 10㎛ 5.0 5.3811 V 0.3811V 5 / 7㎛ 5 / 13㎛ 5.0 5.3217V 0.3217 V 5 / 5㎛ 5 / 15㎛ 5.0 5.2834 V 0.2834 V

As can be seen in Table 1, as the channel length of the transistor M4_2 increases, the kickback voltage of the node B decreases. That is, by making the channel length of the transistor M4_2 longer than the channel length of the transistor M4_1, the current I _OLED corresponding to the applied data voltage can be applied to the organic light emitting diode OLED more stably. Can be improved.

In the second embodiment of the present invention, two transistors M4_1 and M4_2 connected in series are used. However, the present invention is not limited thereto, and a double gate transistor in which two gate electrodes are formed in one transistor may be used.

6 is an equivalent circuit diagram illustrating a pixel circuit 130 according to a third embodiment of the present invention. The pixel circuit 130 according to the third embodiment of the present invention uses the dual transistors M3_1 and M3_2 to reduce kickback voltages caused by parasitic voltages between the gate and the source of the transistor M1. different.

The pixel circuit 130 includes seven transistors M1, M2, M3_1, M3_2, M4_1, M4_2, and M5, two capacitors Cst and Cvth, and an organic light emitting diode OLED. The pixel circuit 130 includes five transistors M1, M2, M4_1, M4_2, and M5, two capacitors Cst and Cvth and an organic light emitting diode OLED, except for the transistors M3_1 and M3_2. Is the same as the pixel circuit 120, and the operation thereof is also the same, so a detailed description thereof will be omitted.

On the other hand, transistor M3_2 has a source connected to the drain of transistor M1 and a drain connected to the source of transistor M3_1. The drain of the transistor M3_1 is connected to the gate of the transistor M1. That is, the two transistors M3_1 and M3_2 form a double transistor connected in series with each other. In addition, the gates of both transistors M3_1 and M3_2 are directly connected to the scan line Sn-1. Therefore, in response to the previous selection signal, the two transistors M3_1 and M3_2 are simultaneously turned on to diode-connect transistor M1.

As shown in FIG. 6, by using the double transistors M3_1 and M3_2, the transistors M3_1 and M3_2 are turned off by the signal of the previous scanning line Sn−1, and the transistors are driven by the signal of the current scanning line Sn. When the voltage M5 is turned on and a voltage corresponding to the data voltage is applied to the gate node A of the transistor M1 through the capacitor Cst and the capacitor Cvth, the kickback voltage at the node A may be reduced. . Therefore, the gate node A of the transistor M1 is less affected by the voltage change due to the kickback voltage. Therefore, the voltage Vgs between the gate and the source of the transistor M1 is small due to the kickback voltage. The effect on the kickback of the current (I _OLED ) delivered to can be significantly reduced.

Here, when the total size of the double transistors M3_1 and M4_2, that is, the total channel length L, is constant, a larger channel length of the transistor M3_2 than the channel length of the transistor M3_1 reduces the kickback voltage more effectively. Can be.

Table 2 shows that when the channel width W of each of the double transistors M3_1 and M3_2 is 5 μm and the total channel length L of the two transistors is 20 μm, the channel lengths of the transistors M3_1 and M3_2 are determined. Accordingly, the result of measuring the voltage of the node A when the double transistors M3_1 and M3_2 are turned on, that is, the voltage of the gate of the transistor M1 and the voltage of the gate of the transistor M1 when the transistors M1 are turned off.

Size of transistor Gate voltage of transistor M1 Kickback voltage M3_1 (W / L) M3_2 (W / L) On turn On turn off 5 / 15㎛ 5/5 3.6570 V 4.6653V 1.0083 V 5 / 10㎛ 5/10 3.2503 V 4.1223V 0.8720 V 5 / 7㎛ 5/13 3.1370V 3.9445 V 0.8075 V 5 / 5㎛ 5/15 3.0791V 3.8463V 0.7672 V

As can be seen in Table 2, as the channel length of the transistor M3_2 is longer, the magnitude of the kickback voltage of the gate of the node A, that is, the transistor M1, decreases. That is, by making the channel length of the transistor M3_2 longer than the channel length of the transistor M3_1, the current I _OLED corresponding to the applied data voltage can be applied to the organic light emitting diode OLED more stably. Can be improved.

In Tables 1 and 2, the minimum channel length of the transistors M3_1 and M4_1 is 5 μm, but if the transistor is formed with a channel length smaller than 5 μm in the transistor fabrication process, the transistor characteristics are ensured. And the channel length of the transistor M4_1 can be made smaller than 5 mu m. As the channel lengths of the transistors M3_1 and M4_1 are smaller, the parasitic capacitance component is reduced, so that the influence on the kickback can be more effectively reduced.

In the third embodiment of the present invention, the double transistors M3_1 and M3_2 connected in series with two transistors are used. However, the present invention is not limited thereto, and a double gate transistor in which two gate electrodes are formed in one transistor may be used.

Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to the same structure as the embodiments, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the claims are also provided. It belongs to the scope of the invention.

According to the present invention, by using the double transistor, the kickback voltage due to the parasitic capacitor component present in the pixel circuit can be reduced.

In particular, by forming the transistors connected in parallel with the storage capacitor for storing the voltage corresponding to the applied data voltage as a double transistor of different sizes, it is possible to effectively reduce the effect of kickback on one electrode of the storage capacitor. In addition, by reducing the kickback voltage due to parasitic capacitance between the gate and the source / drain of the driving transistor for driving the organic light emitting diode, the effect of the kickback on the gate of the driving transistor can be effectively reduced by forming double transistors of different sizes. .

As such, the display characteristics of the light emitting display device can be improved by effectively reducing the influence of the kickback.

Claims (16)

A light emitting display device comprising: a plurality of data lines for transmitting a data voltage, a plurality of scanning lines for transmitting a selection signal, and a plurality of pixel circuits electrically connected to the scanning lines and the data lines. The pixel circuit, First and second transistors each turned on in response to the first control signal and connected in series with each other; A first capacitor connected in parallel with the first and second transistors connected in series; A third transistor applying the data voltage to the first electrode of the first capacitor in response to the selection signal; A fourth transistor outputting a current corresponding to a gate-source voltage depending on the voltage of the first capacitor; And And a light emitting device that emits light corresponding to the current from the fourth transistor. The method of claim 1, The first electrode of the first transistor is connected to the first electrode of the first capacitor, the second electrode of the first transistor is connected to the first electrode of the second transistor, and the second electrode of the second transistor. The light emitting display device is connected to the second electrode of the first capacitor. The method of claim 2, A light emitting display device in which a double gate transistor is formed by the first and second transistors. The method of claim 2, The first and second transistors have different sizes. The method of claim 4, wherein The channel length of the second transistor is longer than the channel length of the first transistor. The method of claim 1, The pixel circuit A second capacitor connected between the first electrode of the first capacitor and the gate of the fourth transistor; And And a first switch configured to connect the fourth transistor in the form of a diode in response to the first control signal. And a gate of the fourth transistor is connected to a second electrode of a second capacitor, and a source of the fourth transistor is connected to a second electrode of the first capacitor to output the current. The method of claim 6, The first switch further includes fifth and sixth transistors turned on in response to the first control signal and connected in series. The method of claim 7, wherein A light emitting display device in which a double gate transistor is formed by the fifth and sixth transistors. The method of claim 8, A second switch configured to transfer a current output from the fourth transistor to the light emitting device in response to a second control signal; The second control signal is applied after the first control signal and the selection signal. The method of claim 1, And the first control signal is a previous selection signal applied before the selection signal. The method according to any one of claims 1 to 10, The light emitting device is a light emitting display device that uses light emission of an organic material. A light emitting display device comprising a plurality of data lines transferring a data voltage, a plurality of scan lines respectively transmitting a selection signal including first and second selection signals, and a plurality of pixel circuits electrically connected to the scan lines and the data lines. To The pixel circuit, A first transistor having a first main electrode connected to the data line and a second main electrode turned on in response to the second selection signal to transfer the data voltage; A first capacitor storing a voltage corresponding to the data voltage transferred by the first transistor; Second and third transistors connected in series with each other and turned on in response to the first selection signal to be connected in parallel with the first capacitor; A fourth transistor outputting a current corresponding to the voltage stored in the first capacitor; Fifth and sixth transistors connected in series with each other and turned on in response to the first selection signal to connect the first transistor in the form of a diode; A second capacitor connected to a first electrode of the first capacitor and the fourth transistor between a control electrode to store a voltage corresponding to the threshold voltage of the fourth transistor; And And a light emitting device emitting light corresponding to the current output from the fourth transistor. The method of claim 12, The second and third transistors have different sizes from each other. The method of claim 13, The first and second transistors of the second and third transistors electrically contacting the second main electrode of the first transistor have a shorter channel length than the other transistor. The method of claim 12, The fifth and sixth transistors have different sizes. The method of claim 15, The light emitting display device of one of the fifth and sixth transistors which is in electrical contact with the control electrode of the fourth transistor has a shorter channel length than the other transistor.

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