Method and system for setting correction coefficients for transistors

Abstract

To provide a system and method for estimating a transistor parameter.SOLUTION: A correction coefficient setting method of a drive transistor includes a step 305 for determining respective current measurement values to a plurality of transistor control voltages, a step 310 for setting a first correction coefficient of the transistor on the basis of the transistor current measurement values and the transistor control voltages, and a step for applying a voltage corresponding to a color value to a gate of the transistor on the basis of the first correction coefficient. Further, it may include a step 320 for setting an addition correction coefficient.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method and system for setting a correction coefficient for a transistor.

[0002] This application claims priority to U.S. Patent Application No. 63 / 062,898, filed in the United States Patent and Trademark Office on August 7, 2020, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] In systems that include transistors with uncertain parameters or that include multiple transistors with different parameters, it is advantageous to drive the transistors with circuitry that compensates for the parameter uncertainties or differences. Systems and methods for estimating transistor parameters can be used for this purpose. Summary of the Invention [Problem to be solved by the invention]

[0004] The problem that the present invention seeks to solve is to provide a system and method for estimating transistor parameters. [Means for solving the problem]

[0005] A method for setting a correction coefficient of a transistor according to one embodiment of the present invention includes determining transistor current measurements for a plurality of transistor control voltages, setting a first correction coefficient of the transistor based on the transistor current measurements and the transistor control voltages, and applying a voltage corresponding to a color value to a gate of the transistor based on the first correction coefficient.

[0006] According to one embodiment of the present invention, the method further includes setting an additive correction factor, the first correction factor being a multiplicative correction factor, and setting the multiplicative correction factor and the additive correction factor may include estimating a plurality of parameters of the transistor.

[0007] According to an embodiment of the present invention, the parameters may include alpha, threshold voltage and mobility.

[0008] According to an embodiment of the invention, estimating the plurality of parameters may include solving two equations for the alpha and the threshold voltage.

[0009] According to an embodiment of the present invention, each of the two equations may depend only on the alpha and the threshold voltage of the parameters of the transistor.

[0010] According to one embodiment of the present invention, JPEG0007629817000001.jpg1870 JPEG0007629817000002.jpg1719 and I 1 is a first one of the transistor current measurements, and I 2 is a second one of the transistor current measurements, and I 3 is a third current measurement of the transistor current, I 4 is the fourth of the transistor current measurements, and Vgs 1 is a transistor control voltage corresponding to the first current among the plurality of transistor control voltages, and Vgs 2 is a transistor control voltage corresponding to the second current among the plurality of transistor control voltages, and Vgs 3 is a transistor control voltage corresponding to the third current among the plurality of transistor control voltages, and Vgs 4 is a transistor control voltage corresponding to the fourth current among the plurality of transistor control voltages, and V thmay be the threshold voltage and α may be the alpha.

[0011] According to one embodiment of the present invention, JPEG0007629817000003.jpg1932 JPEG0007629817000004.jpg1710 and I 1 is a first one of the transistor current measurements, and I 2 is a second one of the transistor current measurements, and Vgs 1 is a transistor control voltage corresponding to the first current among the plurality of transistor control voltages, and Vgs 2 is a transistor control voltage corresponding to the second current among the plurality of transistor control voltages, and V th may be the threshold voltage and α may be the alpha.

[0012] According to one embodiment of the present invention, solving the two equations includes finding an approximate numerical solution for the alpha and the threshold voltage, which may minimize the degree of error as long as the two equations are satisfied.

[0013] The method for setting a correction factor according to an embodiment of the present invention may further include obtaining a solution for the mobility by a least squares fit based on the alpha and the threshold voltage.

[0014] According to an embodiment of the present invention, the parameters may further include a bias current.

[0015] The correction factor setting method according to an embodiment of the present invention may further include finding a solution for the bias current by a least squares fit based on the alpha, the threshold voltage, and the mobility.

[0016] According to an embodiment of the present invention, estimating the plurality of parameters may include solving an equation for the threshold voltage, the equation depending only on the threshold voltage of the parameters of the transistor.

[0017] According to one embodiment of the present invention, JPEG0007629817000005.jpg3041 JPEG0007629817000006.jpg2522 and I 1 is a first one of the transistor current measurements, and I 2 is a second one of the transistor current measurements, and I 3 is a third current measurement of the transistor current, I 4 is the fourth of the transistor current measurements, and Vgs 1 is a transistor control voltage corresponding to the first current among the plurality of transistor control voltages, and Vgs 2 is a transistor control voltage corresponding to the second current among the plurality of transistor control voltages, and Vgs 3 is a transistor control voltage corresponding to the third current among the plurality of transistor control voltages, and Vgs 4 is a transistor control voltage corresponding to the fourth current among the plurality of transistor control voltages, and V th may be the threshold voltage.

[0018] The correction factor setting method according to an embodiment of the present invention may further include setting the additive correction factor to a value within 20% of a value corresponding to an effective threshold voltage of zero.

[0019] A correction factor setting method according to an embodiment of the present invention may further include setting the multiplication correction factor to a value within 20% of a value corresponding to an effective mobility equal to a reference mobility.

[0020] According to one embodiment of the present invention, the method may further include the steps of setting an additive correction factor, a multiplicative correction factor being the first correction factor, setting the voltage at the gate based on the additive correction factor and the color value, measuring a difference between a current driven by the transistor and a reference current, and adjusting the multiplicative correction factor and the additive correction factor based on the difference.

[0021] A system according to one embodiment of the present invention includes a processing circuit, a power source, a light-emitting element, and a transistor connected between the power source and the light-emitting element, wherein the processing circuit determines transistor current measurements for a plurality of transistor control voltages, and sets a first correction factor for the transistor based on the transistor current measurements and the transistor control voltage.

[0022] According to one embodiment of the invention, the first correction factor is a multiplicative correction factor and the processing circuit sets an additive correction factor, and setting the multiplicative correction factor and the additive correction factor includes estimating a plurality of parameters of the transistor, and the plurality of parameters may include alpha, threshold voltage, and mobility.

[0023] According to one embodiment of the invention, estimating the plurality of parameters may include solving two equations for the alpha and the threshold voltage, each of the two equations depending only on the alpha and the threshold voltage of the parameters of the transistor.

[0024] A system according to one embodiment of the present invention includes a processing means, a power source, a light-emitting element, and a transistor connected between the power source and the light-emitting element, wherein the processing means determines transistor current measurements for a plurality of transistor control voltages, and sets a first correction factor for the transistor based on the transistor current measurements and the transistor control voltage. Effect of the Invention

[0025] In this way, the transistor parameters can be estimated. [Brief description of the drawings]

[0026] [Figure 1] FIG. 2 is a block diagram of a circuit including a transistor according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram of a circuit including a transistor according to an embodiment of the present invention. [Diagram 3] 2 is a flow chart illustrating a transistor parameter estimation and correction method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The detailed description given below with reference to the accompanying drawings relates to embodiments of a transistor parameter estimation system and method, and does not represent all aspects realized or utilized by the embodiments of the present invention. The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the same or equivalent functions and structures realized in different embodiments are also included within the scope of the present invention. The same reference numerals are used throughout the specification to refer to the same or similar components.

[0028] Referring to FIG. 1, in a video display device such as a computer monitor, a number of light-emitting pixels may each include a drive transistor 115 that drives a current to a light-emitting element such as a light-emitting diode 120 in response to a brightness control signal or a color value. The drive transistor 115 may be a field-effect transistor (FET) connected to a power source 125. A display device may include a large number of such drive transistors, and the drive transistors may not be completely ideal. In such a system (and other systems in which transistors must be controlled), it is desirable to compensate for variations in transistor parameters and provide substantially the same brightness regardless of which pixel is applied to a given brightness control signal (e.g., a digital control signal received by a computer video card) to specify the brightness that must be achieved.

[0029] In such a system, parameters can be estimated for each transistor, and a control voltage can be applied to each transistor based on the brightness control signal and the transistor's parameters. The control voltage can be adjusted [e.g., by processing circuitry 105 (described in more detail below) and digital-to-analog converter 110] to correct for differences between the parameters of the driving transistor and the reference transistor. For example, a multiplicative correction factor can be applied (i.e., multiplied) to the brightness control signal, and an additive correction factor can be applied to the product (of the brightness control signal and the multiplicative correction factor) such that the transistor can drive substantially the same current as a reference transistor (which can be a hypothetical, "ideal" transistor) drives for the same brightness control signal when the correction factors [i.e., the multiplicative correction factor and the additive correction factor] are set to nominal values.

[0030] The parameters of the transistor may be estimated by measuring the current driven by the transistor (i.e., determining the measured transistor current) for each of a number of transistor control voltages, where "transistor drive current" is the current that flows through the transistor's channel (i.e., between the source and drain), and where "control voltage" or "transistor control voltage" is the gate-source voltage.

[0031] From the measured transistor current and transistor control voltage, the transistor parameters can be estimated and the initial values ​​of the correction factors (i.e., the multiplicative and additive correction factors) can be set based on such parameters. Such parameters include, for a FET, the threshold voltage V th , mobility M, alpha α and bias current I bias Such a parameterized transistor model may include:

[0032] I DS =M*(V gs -V th ) α +I bias

[0033] The terms "alpha" and "α" are synonymous and may be used interchangeably herein. As stated above, alpha refers to the exponent of the equation relating the voltage applied to a transistor input to the current at its output. Bias current, sometimes called leakage current, refers to the current that flows through a transistor in the off state.

[0034] According to one embodiment of the present invention, the parameters may be estimated from a number of transistor current measurements determined respectively for a number of transistor control voltages as follows: 1 , I 2 , I 3 , I 4 and the corresponding control voltage is Vgs 1 , Vgs 2 , Vgs 3 , Vgs4 Substituting the measured transistor currents and transistor control voltages into the transistor model results in the following four equations:

[0035] I 1 =(Vgs 1 -V th ) α *M+I bias I 2 =(Vgs 2 -V th ) α *M+I bias I 3 =(Vgs 3 -V th ) α *M+I bias I 4 =(Vgs 4 -V th ) α *M+I bias

[0036] Combining these equations in pairs (e.g., subtracting), we get the bias term I bias We arrive at three equations with

[0037] I 2 -I 1 =M*[(Vgs 2 -V th ) α -(Vgs 1 -V th ) α ] I 4 -I 2 =M*[(Vgs 4 -V th ) α -(Vgs 2 -V th ) α ] I 4 -I 3 =M*[(Vgs 4 -V th ) α -(Vgs 3 -V th )α ]

[0038] The above three equations are based on six possible values ​​(the number of cases where two are selected from four, i.e. 4 C 2 ) are three such equations. According to an embodiment of the present invention, more than four transistor currents can be measured (or a smaller number can be measured as described below) to create a set of different pairs. The three equations above can be paired and combined (e.g., a ratio can be taken) to obtain, for example, two equations after the mobility M is also eliminated.

[0039] JPEG0007629817000007.jpg4194

[0040] Thus, each of the two equations depends only on the transistor parameters alpha and threshold voltage. The two equations above are two independent equations with two unknowns, V th and α. This can be done, for example, by performing a gradient descent optimization or by solving for V th and α, and perform an exhaustive search over the grid of values ​​to minimize the cost function {V th This can be achieved by finding a set of {α,α} values, where the grid is V th The range of plausible values ​​for each of and α (e.g., V th The ranges are 0 V to 0.7 V for α and 1.5 to 2.5 for α. In this way, an approximate numerical solution for alpha and the threshold voltage can be found that minimizes a cost function, which can be the order of the error in the range in which the two equations are satisfied. The cost function is the mean squared error, defined, for example, as follows:

[0041] JPEG0007629817000008.jpg1668

[0042] V th and α value satisfy the above equation, for example, V th and for such values ​​of α, JPEG0007629817000009.jpg1971 JPEG0007629817000010.jpg1717 or, according to one embodiment of the invention, this value may be slightly different, for example: JPEG0007629817000011.jpg1769 JPEG0007629817000012.jpg1618 In this case, the value is within 50% of

[0043] V th Once the values ​​of and α are found, the mobility M can be found from the following equation (which is three equations with one unknown):

[0044] I 2- I 1 =M*[(Vgs 2 -V th ) α- (Vgs 1 -V th ) α ] I 4- I 2 =M*[(Vgs 4 -V th ) α- (Vgs 2 -V th ) α ] I 4- I 3 =M*[(Vgs 4 -V th ) α- (Vgs 3 -V th ) α ]

[0045] This equation forms an overdetermined system of linear equations which can be solved by writing them in the following form:

[0046] JPEG0007629817000013.jpg2250 Here, k1 = [(Vgs 2 -V th ) α -(Vgs 1 -V th ) α ], where k2 and k3 are similarly defined.

[0047] Solving this leads to the following equation: JPEG0007629817000014.jpg925

[0048] TIFF0007629817000015.tif27170

[0049] TIFF0007629817000016.tif24170

[0050] To find the bias, we consider the following overdetermined system: bias can be solved.

[0051] JPEG0007629817000017.jpg2990

[0052] Solving this system using a least squares fit gives I bias The solution to is the average of the four bias currents. [This can be found by solving the transistor model four times for the bias currents, each time using (i) a different one of the measured transistor currents, and (ii) the appropriate transistor control voltage.]

[0053] In some cases, the leakage current I biascan be neglected (i.e. there is no leakage). The unbiased transistor model can be written as

[0054] I DS =M*(V gs -V th ) α

[0055] In this model, α, Vth,M are unknown parameters that must be estimated. Mobility can be eliminated by finding the ratio of (i) the unbiased transistor model at the first measurement of the transistor current and the corresponding transistor control voltage to (ii) the unbiased transistor model at the second measurement of the transistor current and the corresponding transistor control voltage.

[0056] JPEG0007629817000018.jpg1846

[0057] From this equation, the unknown V th This leads to the following equation, where

[0058] JPEG0007629817000019.jpg1842

[0059] For additional transistor current measurements and the corresponding transistor control voltages, see V th We can derive a different equation with unknowns:

[0060] JPEG0007629817000020.jpg1744

[0061] Each of the above two equations depends only on the transistor parameters alpha and threshold voltage. Taking the logarithm on both sides of each of the two equations results in the following equation:

[0062] JPEG0007629817000021.jpg3765

[0063] By taking the ratio of the two equations, the parameter α can be eliminated.

[0064] JPEG0007629817000022.jpg2860

[0065] This equation depends only on the threshold voltage of the transistor, and can be iteratively calculated as V th For example, we can find a solution to V th This can be done by performing an exhaustive search over the entire grid of values ​​of V th (eg, ranging from 0V to 0.7V)]. According to one embodiment of the present invention, the transistor control voltages can be selected as follows:

[0066] JPEG0007629817000023.jpg1521

[0067] (Example: Current is I 1 =1nA,I 2 =2nA,I 3 =2.5nA,I 4 = 5nA or may be within 30% of this value).

[0068] In this case, V th can be calculated directly as follows:

[0069] JPEG0007629817000024.jpg1863

[0070] According to one embodiment of the present invention, V th It is possible to find similar (but not necessarily identical) values ​​for . For example, JPEG0007629817000025.jpg2939 is JPEG0007629817000026.jpg2721 The value is within 50% of the above.

[0071] V th Using the values ​​of , we can find α and M as follows:

[0072] JPEG0007629817000027.jpg3995

[0073] V th and the value of α is JPEG0007629817000028.jpg1729 JPEG0007629817000029.jpg178 It has the property of having a value within 50% of.

[0074] Since α and M can be calculated using multiple transistor current measurements and the corresponding transistor control voltages, a least squares fit method can be used to calculate alpha.

[0075] JPEG0007629817000030.jpg941 or JPEG0007629817000031.jpg750

[0076] Next, α and M can be calculated as follows:

[0077] JPEG0007629817000032.jpg3272

[0078] The above method uses four transistor current measurements, which in the unbiased case yield three parameters: th , alpha, M), three transistor current measurements are sufficient to solve for the three parameters, and in accordance with one embodiment of the present invention, only three transistor current measurements are used.

[0079] Once the transistor parameters are estimated, the correction factors (i.e., multiplicative and additive correction factors) can be calculated as follows: Figure 2 shows a transistor control circuit according to one embodiment of the present invention. A reference current source 205 is provided that: (i) M ideal *C in 2 [M ideal is the reference mobility, C in (ii) a processing circuit 210 that calculates a control word (representing the requested pixel brightness), and (iii) a current digital-to-analog converter (or “current DAC”) 215 that includes a function I ref =M ideal K V2I C in 2 The reference current is generated according to the reference mobility M ideal can be selected to be within the range of possible values ​​of M, for example, to be the mobility value when there are no manufacturing variations and aging changes in the transistor characteristics. in and calculating an adjusted transistor control voltage based on the correction factors), a digital-to-analog converter 110, and a transistor 115. The processing circuit 105 used to apply the corrections (i.e., the multiplicative and additive correction factors) may be any appropriately configured processing circuit (e.g., in firmware or software) and may be referred to as a "compensation circuit." The processing circuit 105 of the driver circuit 220 may share components with (e.g., may be the same processing circuit) the processing circuit 210 of the reference current source 205. The reference mobility μ ideal , I ref DAC215 Gain K V2I , and the gain K of the digital-to-analog converter of the driver circuit 220 D is known.

[0080] The unknown parameter is the V th (V th_actual ), i.e., the actual threshold voltage and the M (M actualSuch unknown parameters include the actual mobility, i.e., the charge transport coefficient, i.e., the charge transport coefficient (hereinafter referred to as the charge transport coefficient), which are estimated, for example, from transistor current measurements and corresponding transistor control voltages as previously described.

[0081] The initial values ​​of the correction factors (ie, multiplicative correction factor A and additive correction factor B) can be calculated as follows:

[0082] JPEG0007629817000033.jpg28152

[0083] I ref =I pixel In the case of K D B=V th_actual If we choose B so that (B=V th_actual / K D ) the above equation becomes:

[0084] JPEG0007629817000034.jpg1291

[0085] Solving this for A gives the following equation:

[0086] JPEG0007629817000035.jpg1186

[0087] Using the above A and B values, the combination of compensation circuit 105, digital-to-analog converter 110 and transistor 115 can have substantially the same characteristics as an uncompensated transistor having a threshold voltage of zero, a reference mobility, and driven through digital-to-analog converter 110 with the same gain. Thus, the above A and B values ​​apply when the effective threshold voltage is zero and the effective mobility is the same as the reference mobility. The A and B values ​​derived above can be used as initial values ​​and adjusted accordingly based on the residual error measured when applying the compensation factors (i.e., the multiplicative compensation factor and the additive compensation factor) (each of the residual errors being a measured difference between (i) the intended or "reference" current driven through the light emitting element and (ii) the transistor drive current). For example, it can be applied as described in U.S. Patent Application No. 16 / 657,680, entitled "ESTIMATION OF PIXEL COMPENSATION COEFFICIENTS BY ADAPTATION," filed on October 18, 2019, which is incorporated herein by reference.

[0088] 3 is a flow chart according to one embodiment of the present invention, in which the method determines a number of transistor current measurements (e.g., each corresponding to one of a number of transistor control voltages) in step 305, sets initial values ​​for the multiplicative and additive correction factors (e.g., based on the current measurements and the control voltages) in step 310, and adjusts the multiplicative and additive correction factors accordingly, for example, by measuring a residual error in step 315, and adjusting the multiplicative and additive correction factors in step 320.

[0089] Here, a "portion" of something means "at least some" of it, which may mean less than or all of it. Thus, a "portion" of something may include its whole as a special case; that is, its whole is an example of a part of it. Here, a "rectangle" includes a square as a special case; that is, a square is an example of a rectangle, and "rectangular" includes a "square." Here, if a second number is within Y% of a first number, this means that the second number is greater than or equal to (1-Y / 100) times the first number and less than or equal to (1+Y / 100) times the first number. Here, the term "or" should be interpreted as "and / or," e.g., "A or B" means one of "A" or "B" or "A and B."

[0090] The term "processing circuitry" or "processing means" as used herein refers to a combination of hardware, firmware, and software used to process data or digital signals. The processing circuitry may include, for example, an application specific integrated circuit (ASIC), a general purpose or dedicated central processing unit (CPU), a digital signal processor (DSP), a graphics processing unit (GPU), a programmable logic device such as an FPGA. In the processing circuitry, each function may be performed by hardwired hardware that performs that function, or by general purpose hardware such as a CPU that executes instructions stored on a non-transitory storage medium. The processing circuitry may be formed on a printed circuit board (PCB) or distributed across the interconnected PCBs. The processing circuitry may include other processing circuits, but may also include, for example, an FPGA and a CPU that are interconnected on a PCB.

[0091] As used herein, when a method (e.g., an adjustment) or a first quantity [e.g., a first variable] is "based on" a second quantity (e.g., a second variable), it means that the second quantity is an input to the method or affects the first quantity, for example, that the second quantity is an input (e.g., one of the single input or multiple inputs) of a function that calculates the first quantity, that the first quantity is equal to the second quantity, or that the first quantity is the same as the second quantity (e.g., stored in the same place in memory).

[0092] Terms such as "first," "second," and "third" are used to refer to various elements, components, regions, layers, sections, etc., but are not limited by such modifiers. Such terms are used to distinguish one element, component, region, layer, section from another element, component, region, layer, section, without departing from the spirit and scope of the present invention.

[0093] The terms used herein are used only for the purpose of describing specific embodiments and are not intended to limit the present invention. In this specification, the terms "substantially," "about," "generally," and similar terms are used to indicate approximations, not to indicate "degrees," but to indicate inherent errors in measurements or calculations that can be recognized by those of ordinary skill in the art.

[0094] Unless otherwise specified, numbers herein include all cases of singular or plural. The term "comprising" a feature, step, operation, part, component, etc. means that the relevant part may be included as well as other features, steps, operations, parts, components, etc. The term "and / or" includes all combinations of one or more of the listed items. The term "at least one" or the like preceding a list modifies the entire list, not each individual item in the list. In addition, the term "may" when used in describing an embodiment of the present invention means that the term is applicable to one or more embodiments of the present invention. The term "exemplary" refers to an example or drawing. The terms "use," "utilization," and the like, along with other similar terms, are used in a similar manner.

[0095] When a part, layer, region, component, etc. is described as being "on" or "connected" to another part, layer, region, component, etc., this includes not only the case where it is "directly" on or directly connected, but also the case where there is another part, layer, region, component, etc. in between. However, when it is described as being "directly on" or "directly connected", it means that there are no other parts in between.

[0096] Numerical ranges recited herein include all sub-ranges of the same precision contained within the range. For example, a range "from 1.0 to 10.0" or "between 1.0 and 10.0" includes a minimum value of 1.0 and a maximum value of 10.0, and all sub-ranges therebetween, i.e., sub-ranges having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0, such as 2.4 to 7.6. Maximum values ​​recited herein are inclusive, including all numerical limits lower than them, and minimum values ​​recited herein are inclusive, including all numerical limits higher than them.

[0097] Although embodiments of the transistor parameter estimation system and method have been described and illustrated above, those skilled in the art may change and modify such embodiments. Accordingly, other transistor parameter estimation systems and methods constructed according to the principles presented herein are also encompassed by the present invention. The present invention is defined by the following claims and their equivalents. [Explanation of symbols]

[0098] 105: Processing circuit / correction circuit 110: Digital-to-analog converter 115: Transistor 120: Light emitting diode 205:Reference current source 210: Processing circuit 215:DAC 220: Drive circuit

Claims

1. determining transistor current measurements for a plurality of transistor control voltages; setting a first correction factor for a transistor based on the transistor current measurement and the transistor control voltage; setting a second correction factor; applying a voltage corresponding to a luminance value to a gate of the transistor based on the first correction coefficient and the second correction coefficient; Including, setting the first correction factor and the second correction factor includes estimating a parameter of a transistor; the first correction factor is a multiplication correction factor; the second correction coefficient is an additive correction coefficient, setting the multiplicative correction factor and the additive correction factor includes estimating a plurality of parameters of the transistor; the plurality of parameters include alpha, threshold voltage, and mobility; estimating the plurality of parameters includes combining two of three or more equations to eliminate at least one of the bias current or the mobility of the transistor; The alpha is represented by α in the following formula 1: estimating the plurality of parameters includes solving two equations for the alpha and the threshold voltage; A method for setting a correction coefficient for a transistor, wherein each of the two equations depends only on the alpha and the threshold voltage among the parameters of the transistor. I DS =M*(V gs -V th ) α +I bias (Equation 1) where I DS is the current flowing between the source and drain of the transistor, V gs is the voltage applied between the gate and source of the transistor, M is the mobility, V th is the threshold voltage, I bias is the bias current flowing through the transistor when it is off, and α is the exponent in equation 1.

2. is has a value within 50% of I １ is a first one of the transistor current measurements; I ２ is a second one of the transistor current measurements; I ３ is a third one of the transistor current measurements; I ４ is a fourth one of the transistor current measurements; Vgs １ is a transistor control voltage among the plurality of transistor control voltages corresponding to the first current, Vgs ２ is a transistor control voltage corresponding to the second current among the plurality of transistor control voltages, Vgs ３ is a transistor control voltage corresponding to the third current among the plurality of transistor control voltages, Vgs ４ 2. The correction coefficient setting method according to claim 1, wherein: is a transistor control voltage corresponding to the fourth current among the plurality of transistor control voltages.

3. is has a value within 50% of I １ is a first one of the transistor current measurements; I ２ is a second one of the transistor current measurements; Vgs １ is a transistor control voltage among the plurality of transistor control voltages corresponding to the first current, Vgs ２ 2. The correction coefficient setting method according to claim 1, wherein: is a transistor control voltage corresponding to the second current among the plurality of transistor control voltages.

4. solving the two equations includes obtaining an approximate numerical solution for the alpha and the threshold voltage; 2. The method of claim 1, wherein the approximate numerical solution minimizes the degree of error as long as the two equations are satisfied.

5. 2. The method of claim 1, further comprising the step of: solving for the mobility using a least squares fit based on the alpha and the threshold voltage.

6. The correction coefficient setting method according to claim 5 , wherein the parameters further include the bias current.

7. 7. The method of claim 6, further comprising the step of: solving for the bias current with a least squares fit based on the alpha, the threshold voltage and the mobility.

8. estimating the plurality of parameters includes solving an equation for the threshold voltage; 2. The method of claim 1, wherein the one equation depends only on the threshold voltage of the transistor.

9. is has a value within 50% of I １ is a first one of the transistor current measurements; I ２ is a second one of the transistor current measurements; I ３ is a third one of the transistor current measurements; I ４ is a fourth one of the transistor current measurements; Vgs １ is a transistor control voltage among the plurality of transistor control voltages corresponding to the first current, Vgs ２ is a transistor control voltage corresponding to the second current among the plurality of transistor control voltages, Vgs ３ is a transistor control voltage corresponding to the third current among the plurality of transistor control voltages, Vgs ４ is a transistor control voltage corresponding to the fourth current among the plurality of transistor control voltages.

10. 2. The method of claim 1, further comprising the step of setting the additive correction coefficient to a value within 20% of a value B in the following formula 2, which corresponds to an effective threshold voltage of zero: B=V th_actual / K D (Formula 2) where V th — actual is the actual threshold of the transistor and K D is the gain of the digital-to-analog converter connected to the transistor.

11. 11. The method of claim 10, further comprising the step of setting the multiplication correction factor to a value within 20% of the value in Equation 3 below corresponding to an effective mobility equal to a reference mobility. (Formula 3) where M ideal is an arbitrarily chosen reference mobility and M actual is the actual mobility of the transistor.

12. the first correction factor is a multiplication correction factor; the second correction coefficient is an additive correction coefficient, The method comprises: setting the voltage at the gate based on the multiplicative correction factor, the additive correction factor and the luminance value; measuring a difference between the current driven by the transistor and a reference current; adjusting the multiplicative correction factor and the additive correction factor based on the difference; The correction coefficient setting method according to claim 1 , further comprising:

13. A processing circuit; Power supply, A light-emitting element; a transistor connected between the power source and the light emitting element; Including, The processing circuitry includes: determining transistor current measurements for a plurality of transistor control voltages; determining a first correction factor for a transistor based on the transistor current measurement and the transistor control voltage; Set a second correction factor; setting the first correction factor and the second correction factor includes estimating a parameter of a transistor; the first correction factor is a multiplication correction factor; the second correction coefficient is an additive correction coefficient, setting the multiplicative correction factor and the additive correction factor includes estimating a plurality of parameters of the transistor; the plurality of parameters include alpha, threshold voltage, and mobility; estimating the plurality of parameters includes combining two of three or more equations to eliminate at least one of the bias current or the mobility of the transistor; The alpha is represented by α in the following formula 1: estimating the plurality of parameters includes solving two equations for the alpha and the threshold voltage; wherein each of the two equations depends only on the alpha and the threshold voltage of the transistor parameters. I DS =M*(V gs -V th ) α +I bias (Equation 1) where I DS is the current flowing between the source and drain of the transistor, V gs is the voltage applied between the gate and source of the transistor, M is the mobility, V th is the threshold voltage, I bias is the bias current flowing through the transistor when it is off, and α is the exponent in equation 1.

14. A processing means; Power supply, A light-emitting element; a transistor coupled between the power source and the light emitting device; Including, The processing means includes: determining transistor current measurements for a plurality of transistor control voltages; determining a first correction factor for a transistor based on the transistor current measurement and the transistor control voltage; Set a second correction factor; setting the first correction factor and the second correction factor includes estimating a parameter of a transistor; the first correction factor is a multiplication correction factor; the second correction coefficient is an additive correction coefficient, setting the multiplicative correction factor and the additive correction factor includes estimating a plurality of parameters of the transistor; the plurality of parameters include alpha, threshold voltage, and mobility; estimating the plurality of parameters includes combining two of three or more equations to eliminate at least one of the bias current or the mobility of the transistor; The alpha is represented by α in the following formula 1: estimating the plurality of parameters includes solving two equations for the alpha and the threshold voltage; wherein each of the two equations depends only on the alpha and the threshold voltage of the transistor parameters. I DS =M*(V gs -V th ) α +I bias (Equation 1) where I DS is the current flowing between the source and drain of the transistor, V gs is the voltage applied between the gate and source of the transistor, M is the mobility, V th is the threshold voltage, I bias is the bias current flowing through the transistor when it is off, and α is the exponent in equation 1.

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