KR101462695B1 - Active matrix display and mehtod - Google Patents

Abstract

The active matrix display includes at least one data driver circuit including a column data line and a parallel column current line; A plurality of pixels connected in series to the column data line and the parallel column current line, each pixel including at least one pixel responsive to a column data line voltage to drive a selected pixel current to the at least one pixel; And a voltage difference between the input heat current of the current line and the voltage of the load drawing on the current line at the head of the column and outside the plurality of pixels and adjusts the data programming voltage according to the difference.

Active matrix display, voltage, current, pixel, OLED, transistor

Description

[0001] ACTIVE MATRIX DISPLAY AND MEHTOD [0002]

The present invention relates to an active matrix display and a method of driving the display.

The active matrix display is formed of a plurality of light emitting units called pixels. Each pixel includes an electronic circuit for controlling the light emitting diode. The pixels are arranged in an array of rows and columns to form a display. During operation, each pixel of the array is programmed sequentially with updated data values that are converted to light levels.

In a typical 2-TFT pixel, a data value externally determining brightness is provided in the form of voltage. The voltage is converted by the pixel circuit into a current directed to the organic light emitting diode (OLED). The amount of current determines the amount of light emitted by the diode. When the OLED is programmed, the thin film transistor (TFT) transfers the data value voltage from the program line to the gate of the other transistor, which regulates the current flowing from the voltage source to the OLED.

The current flowing through the current regulating transistor depends on the voltage at the gate of the transistor. Factors such as transistor material properties have a direct effect on the current flowing through the transistor. Transistor material property variations (mismatch) can cause the current for the same programmed voltage level to be different for two different pixels. If so, it can make the light output different. In order to solve this problem, various pixel designs having transistors and control lines of increased number have been proposed. However, these designs are complex structures with reduced yield and aperture ratio.

There is a need for an active matrix display that includes a pixel driver that uses minimal transistors, avoids complicated pixel circuitry, and has fast programmability and improved output uniformity.

The present invention provides an active matrix display with display driver control circuitry that provides a high level of uniformity without increasing the complexity of the display pixels.

The invention relates to a liquid crystal display comprising a plurality of pixels and a data line, a selection line and a current line for the pixel, wherein at least one pixel comprises a circuit having at least two thin film transistors, a capacitor and a light emitting diode, May be described as a display comprising circuitry outside the plurality of pixels that adjusts the voltage of the data line in accordance with a drawn current.

In one embodiment, the present invention provides a method of driving a display device comprising at least one data driver circuit including a column data line and a column current line, a column driver connected to both the column data line and the column current line, A plurality of pixels including at least one pixel responsive to a column data line voltage and a plurality of pixels at the top of the column data line and the column current line and external to the plurality of pixels, And a loopback circuit that adjusts the column data line voltage to program the voltage of the pixel current adjusted to match the external reference current.

In another embodiment, a method for driving an active matrix display includes sensing a voltage difference between a voltage of a first supply current to the active matrix display and a voltage of a current drawn by the programmed pixel; And adjusting a data programming voltage to a pixel of the display in accordance with the difference, wherein the sensing and adjusting comprises: applying a voltage to the top of the row of pixels comprising the pixel and to a loopback Is performed by a control circuit.

In another embodiment, the active matrix display comprises a plurality of AMOLED pixels arranged in matrix columns and rows, each row of pixels connected to a common current line and a common data voltage source, and a row of each pixel connected to a common select line Wherein at least one of the pixels has a drain / source connected to the column current line, a current driving transistor including a gate and a source / drain, a drain / source connected to the column data line, And an OLED connected to the drain / source of the current driving transistor, wherein the plurality of AMOLED pixels are coupled to at least one of the columns At the top and outside the plurality of pixels in the column, Sensing the voltage of the current, it is connected to the loop-back control circuit for controlling the column data line voltage to program a voltage of an adjusted pixel current to match an external reference current.

In yet another embodiment, the present invention provides a semiconductor device comprising at least one column data line, at least one parallel column current line, at least one column data line, and a corresponding parallel column current line, Wherein the at least one pixel drives the pixel current to the at least one pixel in response to the column data line, and at least one of the data lines and the current line, Loopback control circuitry external to a plurality of columns of columns wherein the loopback control circuitry detects a voltage difference between a voltage of a first input data current and a voltage of a load drawing the current line, And adjusting the input data current accordingly.

In another embodiment, a method for driving an active matrix display comprises the steps of: (A) sampling an active matrix display with an initial current indicative of a first program data value from a power supply; (B) Storing the program voltage data value and applying the first program voltage data value to a selected pixel circuit; (C) comparing the first program voltage data value with the next program voltage data value as a result of the pixel attribute change; (D) sensing a voltage of the drawn current and comparing the voltage with a voltage of the sampled initial current signal, (E) comparing the first program voltage data value with the voltage of the sampled initial current signal, Adjusting to a new program voltage data value in a second capacitor, (F) Applying the new program voltage data value, and (G) repeating (B) through (F) until the compared stored program voltage data value is equal to the sampled initial current voltage .

1 is a schematic diagram of a display circuit;

Figure 2 shows a schematic illustration of a display circuit;

3 is a schematic diagram of a display circuit;

Figures 4 and 5 are graphs of the current in the pixel and the current in the driver.

Figs. 6 and 8 are graphs showing the relationship between the data and the current. Fig.

Figures 7 and 9 are graphs as a function of data of current% mismatch.

The brightness of the AMOLED display depends in part on the current through the OLED device. Each pixel circuit of the AMOLED element is programmed to drive a current designed by applying a voltage to a current transistor for a voltage-programmed pixel or by applying a current to a circuit transistor configured differently for a current-programmed pixel.

In a voltage-programmed display, the voltage-to-current conversion is based on the amount representing the ratio of the large signal transconductance of the transistor to the voltage-input of the current-output. The OLED device current varies with the transconductance of the pixel circuit transistor. The transconductance varies across the display and depends on factors such as transistor mobility that can cause nonuniformity both within the display and between the displays. In addition, the voltage programmed pixel may have a sensitivity to a varying transistor threshold voltage on the display and also between the displays.

The present invention relates to a data driver circuit that reduces the complexity of the active matrix backplane and improves AMOLED performance over more complex uniformity correction mechanisms. A driver is a programming circuit or a set of instructions that controls the display. In one embodiment, the present invention provides a data driver for a 2-TFT pixel that provides a high level of uniformity without the need to increase the number of pixel transistors or control lines. The data driver operates within a feedback loop formed by a current line and a data line for a plurality of columns or for each column. The switching circuit distinguishes the individual pixel currents from the rest of the thermal current of the current lines. The current-sense circuit then controls the feedback loop to charge the data line until the desired pixel current level is reached.

BRIEF DESCRIPTION OF THE DRAWINGS The features of the invention will become more apparent from the following detailed description of the preferred embodiments of the invention, given by way of non-limiting example. In the figures, similar structures are identified by the same identification number.

Figure 1 is a schematic diagram of the proposed AMOLED display circuit 10. The circuit 10 includes a plurality of pixels 12 arranged as a matrix array. Figure 1 represents a 3X3 matrix, merely representative of AMOLEDs, which may be formed with thousands of light emitting pixels 12. The 3X3 matrix is shown to include columns A, B, and C and rows R, S, Each pixel 12 is provided between the pixel selection line 26 and the crossing of the pair of column data lines 16 and the column current line 18. [ Each pixel 12 includes an electronic circuit that controls the light emitting diode 14.

Each column includes a data line 16 and a current line 18 and each pixel circuit includes a transistor M1 20 and a transistor M2 22 and a storage capacitor 24. Transistors 20 and 22 are three terminals that can operate in two ways as a switch that allows information to pass in the form of a voltage or as a variable valve that controls the amount of current flowing And source). In each pixel 12, transistor M1 20 has a drain / source connected to the column current line 18, a source / drain connected to diode 14 and a gate connected to the source of transistor M2 22 Driving transistor. The address transistor M2 (22) has a source / drain connected to the gate of the driving transistor M1 (20) and a drain / source connected to the column data line 16. [ Address transistor M2 (22) functions as a switch; When the switch is ON, the voltage on its drain has passed through the source; When the switch is OFF, no voltage can be delivered. Transistor M1 20 functions as a regulating valve that can control the flow of current depending on the state of its gate. As a rule, the amount of voltage at the gate of transistor M1 20 determines the current flowing through this device (from source to drain).

When the column of pixels A, B, or C is updated with new information, the data line 16 provides a data value in the form of a voltage. This is done one row at a time in each pixel 12 of the row for which the corresponding data value is provided simultaneously. The voltage is converted to current by transistor M1 20 and provided by current line 18. [ The current is transferred to the light emitting diode, and the amount of current determines the amount of light emission. Data to the AMOLED is written to that pixel one row at a time, but the diodes operate essentially at 100% duty cycle. This is accomplished by providing one memory circuit per pixel provided as a combination of transistor 22 and capacitor 24. [

During operation, the select line 26 is pulsed to select the pixel 12. Transistor M2 22 is activated by this select line 26 pulse and is switched to the ON state (shown in Fig. 3). In a typical display, when a selected pixel is charged with a stable voltage through the program line 16, a new current I is drawn from the thermal current line 18. Because all other pixels 12 are non-selected, a new current I flows through the selected pixel.

The current flowing through the transistor depends on the voltage at its gate. However, the material properties of the transistors that form the array of pixels may change abruptly across the display area. These factors produce non-uniform brightness levels. Thus, the light output for two different pixels will also vary with the same programmed voltage level. Variations in the properties of the pixels may cause a mismatch across through the device display.

The present invention provides an external control circuit for a display. This control provides a high level of uniformity without increasing display pixel complexity. The present invention lowers the display to have a high aperture ratio (brighter display), lower OLED driving voltage, lower power consumption, higher throughput and lower manufacturing costs. The driver of the present invention can be implemented in standard ICs or integrated on the same panel as the active backplane, further reducing display costs.

2 schematically illustrates an external control circuit 28 of the present invention that is poised to couple with the internal pixel 12. [ The internal circuitry of the pixel 12 includes transistors 20 and 22 and a light emitting diode 14. The external control circuit 28 operates in a feedback loop formed by the data line 16 and the current line 18 at the beginning of each display circuit column, for example, 2 and 3, the external control circuit 28 includes a source / sense module 30 coupled with a data programming module 32. The source /

In operation, the source / sensing module 30 may be programmed to control the programming module 32 to control the programming module 32 to distinguish the individual pixel currents from the rest of the column current of the current line 18 and to obtain the pixel current of the target level Control the feedback loop. The material mismatch characteristics of the pixel transistors 20 and 22 are not disadvantageous because the current sensing and control is performed at the head of the driver column rather than inside the pixel 12. [ In addition, since the same external control circuit 28 is used to program all the pixels of a given column, the pixel current variation is minimized.

3 is a schematic circuit diagram of a display including an external control circuit 28, in accordance with the present invention. As used herein, the term "external control circuit" refers to a control circuit connected to or related to the pixels of the array. For example, an external control circuit may be placed at the head of a column of pixels in a display circuit. In one array, each column of pixels may be associated with its own separate external control circuitry. 3, the source / sense module 30 includes a transistor MSource 34, a transistor MSense 36 and an amplifier Amp1 38. Transistor MSource 34 is a transistor that provides current at a low voltage; Transistor MSense 36 is a transistor that senses a small current change; The amplifier Amp1 38 controls all of the transistors 34 and 36. [ 3 shows one source / sense module 30 including a data programming module 32 in combination with one display column. However, as noted above, the combination of source / sensing module 30 and data programming module 32 is associated with the head of each of the plurality of columns of the display matrix.

The current source / sense module 30 of FIG. 3 provides a control mechanism by the amplifiers Amp1 38, transistor MSense 36 and MSource 34. The amplifier Amp1 38 has three terminals; Two voltage input terminals 46 and 48 identified as '+' and '-', and an output terminal 50 for controlling the gates of transistor MSense 36 and transistor MSource 34. The input terminal 46 is connected to the externally applied constant voltage Vcol. The input terminal 48 is connected to the node nc44. Node nc 44 remains constant at voltage Vcol except for small changes during programming. When the switch MS1 40 is ON the transistor MSense 36 and the transistor Msource 34 gate voltage are determined by the current flowing through the transistor MSense 36 and Msource 34 in response to the current line 18 . If line 18 begins to draw more current, the voltage at node nc 44 and the corresponding input terminal 48 is changed. Amplifier 38 therefore regulates the gate voltage of MSense transistor 36 and Msource transistor 34 in response to a change in voltage of any node nc 44 to produce a current voltage < RTI ID = 0.0 > . As a result, the voltage at the output terminal 50 is changed and the gate of the transistor MSense 36 and Msource 34 is turned on until the current provided by both the MSense 36 and the MSource 34 coincides with the drawn current Is changed.

This voltage change at the gate of the transistor MSense 36 is directly related to the size of the transistor. The larger the transistor, the larger current can be generated at small changes in the gate voltage. On the other hand, the smaller the transistor (with respect to a given small current change), the more the output current can be controlled more accurately by requiring a larger voltage change at its gate.

In Figure 3, the current source / sense module 30, the large transistor MSource 34 and the small transistor MSense 36 can be sized to meet specific display requirements. They are connected via switch MS1 40 and are controlled by amplifier Amp1 38. Element 'A' represents one display row. When operation begins, switch MSl 40 is turned on and most of the thermal current flows through the large transistor MSource 34 (at this point, no current flows through the selected pixel). If the switch MS1 40 is OFF, the voltage at the gate of the large transistor MSource 34 remains constant for each capacitor CS1 42, so that the current provided by the large transistor MSource 34 is also held constant. This operation is referred to as thermal current sampling by transistor MSource 34.

The data programming module 32 of FIG. 3 is connected to the current source / sensing module 30. Data programming module 32 includes amplifier Amp2 52 and a series of switches. The amplifier Amp2 52 includes one input 54 connected to the capacitor CS2 60 and another input 56 connected to the gate of the MSense transistor MS1 36. And the other output terminal 58 is connected to the data line 16 of the column A. [ In the second sampling period, the switch transistor MS2 62 samples the voltage at the gate of the small MSense transistor 36 and stores it in the capacitor CS2 60 (which represents the base level representing the thermal current) And will be used in a later comparison step). At this stage, the current source / sensing module 30 is in the standby / sensing mode and the MSense 36 is sensing a change in the thermal current flowing to the node nc 44. Thus, the amplifier Amp2 52 can regulate the voltage at the gate of the MSense transistor.

During the programming period, the data line 16 is connected to the gate of the transistor M1 (20) via the transistor M2 (22). Transistor M1 20 is always connected to node nc44. This configuration includes a current source / sensing module 30, a data programming module 32, and a feedback loop (not shown) including a pixel transistor M1 (20) across the data line 16 and the current line 18 at node nc 44 Lt; / RTI > The following mechanism occurs in the feed-packet loop when the external data current Idata 64 is injected into node nc 44: (i) Amp1 38 to accept the drawn current of node nc 44, The gate voltage of the MSense 36 is changed; (Current is sensed); (ii) the negative input voltage of Amp2 52 to the positive input 54 is changed to increase the voltage at the output terminal 58 of Amp2 (the injected current flows through transistor M1 20) Which is initially a value of zero); (iii) the output from Amp2 (connected to data line 16) changes the voltage at the gate of transistor M1 20 (data line 16 is adjusted according to the comparison difference); (iv) the current drawn by transistor M1 20 through node nc 44 correspondingly increases. the mechanism of (i) through (iv) is such that the current drawn by transistor Ml 20 through node nc 44 matches the injected data current Idata 64 , And so on until the equivalence is obtained. The current drawn by the M1 20 coincides with the injected current so that the two terminals 56 and 54 of Amp2 52 are equivalent (bring the two terminals 56 and 54 of Amp2 52) to the equivalence. In this equivalent, the voltage at the gate of the MSense 36 returns to the initial value. The feedback loop reaches this equivalent and provides the correct value for the pixel current.

The following examples are illustrative and are not to be construed as limitations on the scope of the claims, unless specifically stated otherwise.

Examples

For purposes of this application, the mobility of a transistor is a device attribute that quantifies the amount of current a transistor of a particular size can provide. In other words, for a given gate voltage, the amount of current flowing is a function of its mobility (among other things). For example, if the same voltage is applied to the gates of two transistors of the same size, but one of them has 20% higher mobility, the higher mobility transistor will provide a further 20% current same). Mobility is a function of material properties and device fabrication, and for the technology used in making the display, mobility can vary across the display area.

For all purposes of this disclosure, the threshold voltage of a transistor is the minimum voltage required to allow current to flow through the transistor gate. The threshold voltage is a function of material properties and device fabrication, and as a result, the threshold voltage may vary across the display area.

Example 1

Circuit simulation was performed using PSPICE® computer software. PSPICE® is computer software for simulating analog and mixed analog and digital circuits and is provided by PO Box 23325, 2655 Seely Avenue through EMA Design Automation Corporation of Rochester, NY 14692, ORCAD of San Jose CA95134. PSPICE® software receives user input circuit schematics and transistor model and addressing information to generate simulation responses.

The circuit schematic was made with simulated PSPICE® to be substantially consistent with the circuits of FIGS. 2 and 3. The signals shown in Fig. 4 are control signals that have activated different switches of the display driver; Specifically, it is the voltage signal that controlled the MS1, MS2 and transistor M2 of the pixel being programmed. The output graph of Figure 5 shows the current through the programmed pixel as a function of time as well as the data current (Idata 64 fed to node nc of the display driver) as a function of time.

The simulated system variables included: (1) total thermal current, which is the sum of all pixel currents in a given column, varying from 150 A to 3500 A; (2) a pixel data current varied from 0.3 A to 20 A; (3) a pixel transistor M1 that is varied in size to emulate a mobility change of up to 25%; (4) a pixel transistor threshold voltage that varies by simulating a change in power up to 50% of the threshold voltage by connecting it to the gate of M1.

The plot of FIG. 5 shows how the pixel current matches the data current. This simulation represents a display driver that is performed under some system conditions to perform the required operation for a given range of conditions.

Figure 5 shows that the proposed display driver has programmed the desired level of current to the intended pixel under all of the system variables described above. The simulation results demonstrate that the circuit can perform pixel addressing with current mismatch correction as intended at the required operating speed and current demand. A quantitative representation of the accuracy can also be extracted from this simulation result.

Example 2

The following example was constructed to compare the programming of the data currents at the display pixels comprising the driving transistor M1 having different properties and to describe its function at different thermal current levels.

The display driver for the display row was fabricated with a single crystal silicon integrated circuit (IC). This column also included test pixel circuits implemented in IC. The test pixel circuits were fabricated to have the same properties except for the M1 transistor size. Two pixels were fabricated with different widths of M1 by 20% to emulate a 20% mobility difference. To emulate a threshold voltage change, an external v power source was connected to that pixel. This power source indicated that the threshold of transistor M1 was changed by 25%.

In the process, LabVIEW® computer software was used to apply the circuit voltage. LabVIEW® computer software was used to control, emulate, and perform instrumental functions of scientific and technical instruments and instrumentation systems. In the first procedure, the voltage level was determined on the program line of each of the two pixels, and then converted to current by M1. To test the performance, the following conditions were changed: (1) the total thermal current varied from 150 내지 to 3000;; (2) the pixel data current changed from 0.5 내지 to 15;; (3) the mobility of the pixel transistor M1 has changed by a change of magnitude up to a change of 20%; (4) The threshold voltage of the pixel transistor M1 was changed by introducing a power source changed by 25%.

FIG. 6 shows the current flow through two pixels Pix1 and Pix2 when programmed in conventional conventional manner. Figure 6 shows the threshold voltage Pix1 increased by 25% and mobility Pix2 increased by 20%. For example, at low data levels, Pix 1 provided about 2.5 μA; At the same data level, Pix2 provided about 4.. This difference made the brightness in the display different, although the two pixels were intended to have the same intensity level (as intended by the same data level).

The plot of Figure 7 shows the normalized percent change between two pixels as a function of the data voltage.

Figures 6 and 7 demonstrate the degree of current variation with changes in M1 properties.

Fig. 8 shows the current programmed through the same two pixels but with the display driver of Fig. 8 shows that although the transistor M1 has a changing property, the two currents of the result are perfectly matched. The normalized percent plot of FIG. 9 shows only the measurement of the tolerance change between the two pixel currents.

Experimental data demonstrate that the non-uniformity of the two pixels driven by the standard technique and adjusting driver of the present invention, respectively, is reduced from 70% to less than 3%. This level of unevenness improves to an order of magnitude over the entire data range. In addition, the programming time can be reduced below the time required by conventional conventional current-copy pixels.

The data driver of the present invention may be implemented on the same panel as the active backplane or in a standard IC. Poly-silicon TFTs provide a good compromise between performance and cost for the proposed driver.

The circuit of the present invention reduces the complexity of the backside of the active matrix by providing a less complex non-uniformity level compared to conventional conventional calibration techniques associated with two transistor TFT pixels. And because the performance requirements for the transistors on the back have been reduced, lower cost technologies can be used for large area arrays.

Although preferred embodiments of the present invention have been described, the present invention should not be limited to the preceding detailed examples, as modifications and variations can be made. The present invention includes modifications and alternatives that fall within the scope of the following claims.

Claims (35)

As a display, A plurality of pixels, each of the plurality of pixels being operatively connected to a data line, a select line, and a current line, wherein at least one pixel comprises two thin film transistors, a capacitor, and a light emitting diode, Wherein the first transistor of the two thin film transistors has a gate connected to the select line and a source or drain connected to the data line, and the second transistor of the two thin film transistors includes a source, A gate coupled to the drain or source of the first transistor and a drain or source coupled to the current line; And Circuitry external to the plurality of pixels, the circuit actively controlling a current value for each of the pixels by adjusting a voltage of the data line according to a current drawn from the current line, A desired pixel current is configured to be drawn from the current line by one of the transistors, Lt; / RTI > Wherein a circuit external to the plurality of pixels adjusts the voltage of the data line in accordance with the current drawn from the current line and the circuit on the outside controls the voltage of the data line determined by the selection line that activates the other one of the transistors Setting the desired pixel current within a single pixel addressing period, Wherein the external circuit actively controls and sets the desired pixel current while the current line simultaneously provides current to other illuminated pixels connected to the same current line. The method according to claim 1, The external circuit does not require measurement data processing through any software or algorithm to actively control and set the desired pixel current value. The method according to claim 1, Wherein the external circuit sets each desired pixel current as a result of the data line voltage adjustments and the data line voltage adjustments result in current line current changes occurring during each pixel addressing period. The method according to claim 1, A circuit external to the display is connected to the data line and the current line, The plurality of pixels connected to the same data line and the same current line all include the at least one pixel responsive to the data line to set a desired pixel current to at least one pixel, A circuit external to the plurality of pixels samples the current of the current line, senses the current of the pixel, compares the current to an external data current, and adjusts the voltage of the data line Adjustable, display. The method according to claim 1, A circuit external to the display is connected to the data line and the current line, The plurality of pixels being all connected to the same data line and the same current line and comprising the at least one pixel responsive to the data line to set a desired pixel current to the at least one pixel, A circuit external to the plurality of pixels samples the current in the current line, senses the current drawn by the at least one pixel, compares the current drawn by the at least one pixel with an external data current , The data line voltage is adjusted according to the difference, and when the value of the current drawn by the at least one pixel is compared with the value of the external data current, loopback circuit operation is repeated until no difference is detected Display. The method according to claim 1, A circuit external to the display is connected to the data line and the current line, The plurality of pixels connected to the same data line and the same current line all include the at least one pixel responsive to the data line to set a desired pixel current to at least one pixel, Wherein the current line is coupled to a pixel current driven transistor source / drain and the data line is coupled to a pixel address transistor source / drain. The method according to claim 1, Wherein the circuitry external to the display comprises a plurality of loopback circuits each connected to a data line and a current line, A plurality of pixels coupled to both the same data line and the same current line comprise the at least one pixel responsive to a voltage of the data line to set a desired pixel current to at least one pixel, For each loopback circuit connected to the same data line and the same current line of the plurality of pixels, the loopback circuit sequentially controls and sets a voltage for each pixel connected to the data line, And to draw a desired current from the display. The method according to claim 1, The plurality of pixels comprising columns of pixels, each column comprising a plurality of pixels connected to column data lines and a column current line, each of the circuits on the outside comprising column data lines and column current lines Wherein the loopback circuitry determines the current at each pixel and adjusts the column data line voltage to adjust the adjusted pixel current until it matches the external reference current, And is configured to program the voltage of the current. 9. The method of claim 8, Wherein the at least one loopback circuit is configured to sample current from a current line, sense a driven pixel current, compare the driven pixel current with the external reference current, and drive the adjusted pixel current according to the difference Adjusts the voltage of the column data line and repeats the loopback circuit operation until no difference is detected when comparing the driven pixel current to the external reference current. 9. The method of claim 8, The at least one loopback circuit further comprises a comparator for comparing a stored level of the pixel current with a voltage associated with an active drawn level of the pixel current and a regulator for regulating the voltage of the column data line according to a comparison with a reference current Display. 9. The method of claim 8, The at least one loopback circuit comprising: a current source including an input terminal coupled to a constant voltage source, an input terminal coupled to the source transistor, and an amplifier having an output terminal switchably connected to a source transistor and a gate of the sense transistor, Module, When the switch is ON, the amplifier activates the source transistor to sample the thermal current, or if the switch is OFF, adjusts the voltage of the sense transistor in response to the difference between the current in the sense transistor and the external reference data current Display. 9. The method of claim 8, Wherein the at least one loopback circuit comprises an amplifier coupled between a sense transistor and a stored level of pixel current and adapted to adjust a voltage of the column data line in response to a difference between a sense transistor voltage and a stored level of the pixel current. Display containing modules. 9. The method of claim 8, The loopback circuit The current source including the amplifier having an input terminal connected to the constant voltage source, an input terminal connected to the source transistor, and an output terminal connected to the gate of the switchable source transistor or the sense transistor, Regulating the voltage of the sense transistor in response to a difference between a current in the sense transistor and an external reference data current when the transistor is activated to sample a thermal current or if the switch is OFF, A data programming module for adjusting the voltage of the column data line in response to a difference between a sense transistor voltage and a stored level of the pixel current, ≪ / RTI > 9. The method of claim 8, At least one pixel is provided between the pixel selection line and each of the intersections of the pair of column data lines and the column current line and the pixel comprises an ON / OFF transistor for providing a selected voltage through the column data line, And a transistor that regulates the current in the thermal current line to the light emitting diode in response to activation by the transistor. 9. The method of claim 8, Wherein at least one of the plurality of pixels comprises a 2-TFT pixel circuit, The first transistor includes a source coupled to receive a data signal, a gate coupled to receive a selection signal, and a drain coupled to a gate of the second transistor, the second transistor having a source coupled to receive a data signal, A display comprising a drain and a source. 9. The method of claim 8, Wherein the at least one loopback circuit comprises: The current source including the amplifier having an input terminal connected to the constant voltage source, an input terminal connected to the source transistor, and an output terminal connected to the gate of the switchable source transistor or the sense transistor, Regulating the voltage of the sense transistor in response to a difference between a current in the sense transistor and a current drawn by a load in the heat current line when the transistor is activated to sample a thermal current or if the switch is OFF, And A data programming module for adjusting the voltage of the column data line in response to a difference between a voltage of the sense transistor and a stored level of the pixel current, / RTI > Wherein at least one of the plurality of pixels comprises a 2-TFT pixel circuit, The first transistor includes a source coupled to receive a data signal, a gate coupled to receive a selection signal, and a drain coupled to a gate of the second transistor, the second transistor having a source coupled to receive a data signal, A display comprising a drain and a source. As a display, A plurality of pixels, each of the plurality of pixels being operatively connected to a data line, a selection line, and a current line, wherein at least one pixel comprises at least two transistors, a capacitor, and a light emitting diode, The gate of one of the transistors being connected to the select line; And Circuitry external to said plurality of pixels, said circuitry comprising means for actively adjusting a current drawn from a current line connected to said pixel by adjusting a voltage of a data line connected to said pixel in accordance with a current of a current line connected to one pixel A current having a desired value is configured to be drawn from a current line connected to the pixel by one of the transistors, Lt; / RTI > The circuitry external to the plurality of pixels actively controls a desired value of current drawn from the current line by the pixel within a time period that is less than a time that the select line remains at a voltage that turns on the transistor in the pixel And the desired pixel current value is set to be drawn from the current line by the pixel while the current line simultaneously provides current to other illuminated pixels connected to the same current line. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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