Amplification circuit for X-ray flat panel detector

Abstract

The utility model provides an amplifying circuit for an X-ray flat panel detector. The amplifying circuit comprises a first transistor, a second transistor and a third transistor, the drain electrode of the first transistor is connected with the second transistor; the source electrode of the first transistor is grounded; the first transistor is connected with the third transistor; the drain electrode of the first transistor is connected with the active pixel unit or the passive pixel unit; a third transistor in the amplifying circuit works as a switching tube, and when the amplifying circuit is connected with an active pixel unit, the active pixel circuit works in different working modes by regulating and controlling the switching tube, so that exposure information of other rows is stored and read when one row works, and the utilization rate of rays is further improved; when the amplification circuit is connected with a passive pixel unit, the amplification circuit is a 3T passive pixel amplification circuit, an amplifier with a signal amplification function is realized in a pixel, and the sensitivity and the signal-to-noise ratio can be improved, so that the detection requirements under the conditions of weak light and low-dose X rays are met.

Description

Technical Field

[0001] The utility model relates to the technical field of amplifier circuits, and in particular to an amplifier circuit for an X-ray flat panel detector. Background Art

[0002] Mainstream commercial flat-panel detectors are mainly based on passive pixel (PPS) sensing circuits based on TFT technology and active pixel (APS) sensing circuits based on CMOS technology.

[0003] Active pixel APS improves the signal-to-noise ratio by integrating common-source or common-drain amplifiers inside the pixel, but in a single pixel, the total pixel area is limited, and the fill rate = photoelectric device area / total area of a single pixel. The more transistors there are, the less area left for the photoelectric device, and the lower the fill rate. The resolution is negatively correlated with the area of a single pixel. The smaller the pixel area, the higher the resolution. However, due to manufacturing process limitations, the increase in the number of transistors will make it impossible to layout within a single pixel, and the pixel area can only be increased, which in turn leads to a decrease in resolution. Therefore, its spatial resolution and fill rate are greatly limited. The active pixel APS has active transistors that can amplify the signal, so it has a higher gain than the passive pixel PPS. However, at the beginning of exposure, the active pixel PPS adopts a row-by-row scanning and exposure mode until all rows are completed. Therefore, when a row is working, other rows are not working but are still exposed, resulting in low utilization of X-rays, and most of the X-ray working time is in an empty exposure state.

[0004] Passive pixel PPS has the advantages of simple structure and high spatial resolution. However, because the passive pixel PPS has no internal amplifier, it needs to use an external charge amplifier for signal amplification, which results in low sensitivity and signal-to-noise ratio, and cannot meet the detection needs under weak light and low-dose X-ray conditions.

[0005] Therefore, in the prior art, there is a problem that the utilization rate of radiation cannot be improved when an active pixel circuit is used, and there is a problem that the signal-to-noise ratio and sensitivity cannot be improved when a passive pixel circuit is used. Utility Model Content

[0006] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide an amplifier circuit for an X-ray flat panel detector, which can solve the problem in the existing technology that the ray utilization rate cannot be improved when using active pixel circuits or the signal-to-noise ratio and sensitivity cannot be improved when using passive pixel circuits.

[0007] In order to solve the above problems, the present invention is implemented according to the following technical solutions:

[0008] An amplifier circuit for an X-ray flat panel detector, comprising:

[0009] a first transistor, a second transistor, and a third transistor;

[0010] The drain of the first transistor is connected to the second transistor;

[0011] The source of the first transistor is grounded;

[0012] The first transistor is connected to the third transistor;

[0013] The drain of the first transistor is connected to the active pixel unit or the passive pixel unit.

[0014] Compared with the prior art, the amplifier circuit for an X-ray flat-panel detector provided by the present invention has the following beneficial effects: the third transistor in the amplifier circuit works as a switch tube. When the amplifier circuit is connected to an active pixel unit, it becomes a 3T1D active pixel circuit. By regulating the switch tube, the active pixel circuit can operate in different working modes, so that when one row is working, the exposure information of other rows can be stored and read, thereby improving the utilization rate of the rays; when the amplifier circuit is connected to a passive pixel unit, it becomes a 3T passive pixel amplifier circuit, realizing an amplifier with a signal amplification function inside the pixel, which can improve sensitivity and signal-to-noise ratio to meet the detection needs under weak light and low-dose X-ray conditions.

[0015] Optionally, the first transistor is a dual-gate thin film transistor; the second transistor is a dual-gate thin film transistor; and the third transistor is a single-gate thin film transistor or a dual-gate thin film transistor.

[0016] Optionally, the drain of the second transistor is connected to a second power supply;

[0017] The source of the second transistor is a signal output terminal.

[0018] Optionally, the drain of the second transistor is connected to the source of the first transistor;

[0019] The source of the second transistor is a signal output terminal.

[0020] Optionally, the drain of the first transistor is connected to the top gate or the bottom gate of the first transistor through the third transistor.

[0021] Optionally, the drain of the first transistor is connected to the top gate or the bottom gate of the second transistor.

[0022] Optionally, the active pixel unit includes a photoelectric device, and the photoelectric device is connected to the drain of the first transistor and a first power supply.

[0023] Optionally, the photoelectric device is a photodiode;

[0024] The first power supply is connected to the cathode of the photodiode;

[0025] The anode of the photodiode is connected to the drain of the first transistor;

[0026] An anode of the photodiode is connected to a top gate or a bottom gate of the second transistor.

[0027] Optionally, the optoelectronic device is a photoelectric device made of a photoconductive material.

[0028] Optionally, the passive pixel unit includes a photodiode and a fourth transistor;

[0029] The cathode of the photodiode is connected to the drain of the first transistor through the fourth transistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the first embodiment of the present utility model;

[0031] Figure 2 This is a schematic diagram of the second embodiment of the present utility model;

[0032] Figure 3 This is a schematic diagram of the third embodiment of the present utility model;

[0033] Figure 4 This is a schematic diagram of a fourth embodiment of the present utility model;

[0034] Figure 5 This is a schematic diagram of the fifth embodiment of the present utility model;

[0035] Figure 6 This is a schematic diagram of the sixth embodiment of the present utility model;

[0036] Figure 7 This is the random read timing diagram for the 3T1D active pixel circuit;

[0037] Figure 8 The integration read timing diagram for the 3T1D active pixel circuit;

[0038] Figure 9 This is the timing diagram of random read and integral read of 3T1D active pixel circuit;

[0039] Figure 10 This is a schematic diagram of the eighth embodiment of the present utility model;

[0040] Figure 11 This is a schematic diagram of a passive pixel unit in the eighth embodiment of the present invention.

[0041] Description of the accompanying drawings: 1. Amplifier circuit. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0043] When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims. In the description of the present application, it should be understood that the terms "first", "second", "third", etc. are only used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0044] Example 1

[0045] See also Figure 1 As shown, this embodiment discloses an amplifier circuit for an X-ray flat panel detector, including: a first dual-gate thin film transistor TFT1, a second dual-gate thin film transistor TFT2 and a third thin film transistor TFT3. In this embodiment, the third thin film transistor TFT3 is a single-gate thin film transistor.

[0046] The drain of the first dual-gate thin film transistor TFT1 is connected to the signal line Signal in Connect the bottom gate of the second dual-gate thin film transistor TFT2 to the signal line Signal in Connection, signal line Signal in The other end is connected to the active pixel unit PPS or the passive pixel unit APS; the drain of the first dual-gate thin film transistor TFT1 is connected to the bottom gate of the first dual-gate thin film transistor TFT1 through the third thin film transistor TFT3, and the third thin film transistor TFT3 is a switch tube; the source of the first dual-gate thin film transistor TFT1 is grounded; the second power supply V DD2 Connected to the drain of the second dual-gate thin film transistor TFT2, the second power supply V DD2 Used to control the switching state of the second dual-gate thin film transistor TFT2; the source of the second dual-gate thin film transistor TFT2 serves as the signal output terminal.

[0047] The top gate of the first dual-gate thin film transistor TFT1 is connected to the peripheral circuit, and the top gate voltage V TG1 , top gate voltage V TG1 It is used to adjust the working area of the first dual-gate thin film transistor TFT1 to the subthreshold region.

[0048] The top gate of the second dual-gate thin film transistor TFT2 is connected to the peripheral circuit, and the top gate voltage V TG2 , top gate voltage V TG2 It is used to adjust the working area of the second dual-gate thin film transistor TFT2 to the subthreshold region.

[0049] The gate of the third thin film transistor TFT3 is connected to the peripheral circuit, and the gate voltage V G3 , gate voltage V G3 It is used to adjust the working area of the third thin film transistor TFT3 to the saturation area, and is also used to control the switching state of the third thin film transistor TFT3, specifically: adjusting the gate voltage V G3 , when the gate voltage V G3 When the threshold voltage is greater than or equal to the drain voltage, the third thin film transistor TFT3 is in the on state; when the gate voltage V G3 When the voltage is less than or equal to the threshold voltage, the third thin film transistor TFT3 is in the off state.

[0050] Example 2

[0051] See also Figure 2 As shown, this embodiment discloses a second amplifier circuit for an X-ray flat panel detector, which differs from the first embodiment in that the third thin film transistor TFT3 is a dual-gate thin film transistor.

[0052] The top gate and bottom gate of the third thin film transistor TFT3 are both connected to the peripheral circuit, and the top gate voltage V TG3 and bottom gate voltage V BG3 , and controls the working state of the third thin film transistor TFT3.

[0053] The amplifier circuit of this embodiment can achieve the same function as the amplifier circuit of the first embodiment.

[0054] Example 3

[0055] See also Figure 3 As shown, this embodiment discloses a third amplifier circuit for an X-ray flat panel detector, which differs from the first embodiment in that the top gate and the bottom gate of the first dual-gate thin film transistor TFT1 are interchanged.

[0056] Specifically, the drain of the first double-gate thin film transistor TFT1 is connected to the top gate of the first double-gate thin film transistor TFT1 through the third thin film transistor TFT3 .

[0057] The bottom gate of the first dual-gate thin film transistor TFT1 is connected to the peripheral circuit, and the bottom gate voltage V of the first dual-gate thin film transistor TFT1 is controlled by the peripheral circuit. BG1 , bottom gate voltage V BG1 It is used to adjust the working area of the first dual-gate thin film transistor TFT1 to the subthreshold region.

[0058] The amplifier circuit of this embodiment can realize the same function as the amplifier circuit of the first embodiment, but the top gate voltage V TG1 and the bottom gate voltage V BG1 The ability to control the threshold voltage of the first dual-gate thin-film transistor TFT1 is different, which is specifically reflected in that the control coefficient γ of the gate voltage to the threshold voltage is related to different manufacturing processes. The larger γ is, the stronger the control ability is. Therefore, compared with the control ability of the amplifier circuit in embodiment 1, the control ability of the amplifier circuit in this embodiment will change.

[0059] Example 4

[0060] See also Figure 4 As shown, this embodiment discloses a fourth amplifier circuit for an X-ray flat panel detector, which differs from the first embodiment in that the top gate and the bottom gate of the second dual-gate thin film transistor TFT2 are interchanged.

[0061] Specifically, the drain of the first double-gate thin film transistor TFT1 is connected to the top gate of the second double-gate thin film transistor TFT2.

[0062] The bottom gate of the second dual-gate thin film transistor TFT2 is connected to the peripheral circuit, and the bottom gate voltage V BG2 , bottom gate voltage V BG2 It is used to adjust the working area of the second dual-gate thin film transistor TFT2 to the subthreshold region.

[0063] The amplifier circuit of this embodiment can achieve the same function as the amplifier circuit of the first embodiment, but the top gate voltage V TG2 and the bottom gate voltage V BG2 The ability to control the threshold voltage of the second dual-gate thin-film transistor TFT2 is different, which is specifically reflected in that the control coefficient γ of the gate voltage to the threshold voltage is related to different manufacturing processes. The larger γ is, the stronger the control ability is. Therefore, compared with the control ability of the amplifier circuit in embodiment 1, the control ability of the amplifier circuit in this embodiment will change.

[0064] Example 5

[0065] See also Figure 5 As shown, this embodiment discloses a fifth amplifier circuit for an X-ray flat panel detector, which differs from the first embodiment in that: the second power supply V DD2The drain of the first double-gate thin film transistor TFT1 is connected to the ground.

[0066] The amplifier circuit of this embodiment is equivalent to the amplifier circuit of the first embodiment.

[0067] Example 6

[0068] Connect the first embodiment to the active pixel unit to form Figure 6 The 3T1D active pixel circuit diagram shown in FIG. 1 is a circuit diagram of a 3T1D active pixel, wherein the active pixel unit includes a photoelectric device. In this embodiment, the photoelectric device is a photodiode PD. The anode of the photodiode PD is connected to the drain of the first dual-gate thin film transistor TFT1 through a signal line, and the cathode of the photodiode PD is connected to the first power supply V DD1 .

[0069] Example 7

[0070] This embodiment discloses a second 3T1D active pixel circuit, which differs from the sixth embodiment in that the optoelectronic device of the active pixel unit is a photoconductive material optoelectronic device; the photoconductive material optoelectronic device includes but is not limited to halides, calcium, titanium, and ore.

[0071] Specifically: the first power supply V DD1 Connected to the optoelectronic device, the first power supply V DD1 Used to provide a reverse bias voltage for the photoelectric device; the photoelectric device is connected to the drain of the first double-gate thin film transistor TFT1; the drain of the first double-gate thin film transistor TFT1 is connected to the bottom gate of the first double-gate thin film transistor TFT1 through the third thin film transistor TFT3, and the third thin film transistor TFT3 is a switch tube; the source of the first double-gate thin film transistor TFT1 is grounded; the photoelectric device is connected to the bottom gate of the second double-gate thin film transistor TFT2; the second power supply V DD2 Connected to the drain of the second dual-gate thin film transistor TFT2, the second power supply V DD2 Used to control the switching state of the second dual-gate thin film transistor TFT2; the source of the second dual-gate thin film transistor TFT2 serves as the signal output terminal.

[0072] The 3T1D active pixel circuit of this embodiment can achieve the same function as the 3T1D active pixel circuit of the sixth embodiment.

[0073] When forming a 3T1D active pixel circuit, three operating states can be achieved by regulating the first dual-gate thin-film transistor TFT1, the second dual-gate thin-film transistor TFT2, and the third thin-film transistor TFT3. The following is a further explanation of the 3T1D active pixel circuit in conjunction with the specific implementation process, as follows:

[0074] The first working state, random reading:

[0075] See also Figure 7 As shown, when the first power supply V DD1 When the bias voltage is positive, the photodiode PD is in a reverse bias state. At this time, the photodiode PD can sense light. Therefore, under the action of the external bias voltage, the photogenerated carriers in the photodiode PD will separate under the action of the electric field and move toward the cathode and anode of the photodiode PD respectively, forming a photocurrent Iphoto, realizing the photoelectric conversion process. At this time, the photodiode PD responds quickly to the light signal and can quickly capture changes in light intensity. The expression of the photocurrent Iphoto is as follows:

[0076]

[0077] Wherein, η0 is the quantum efficiency of the photodiode PD; P is the light power; A is the light receiving area of the photodiode PD; λ is the wavelength of light; R is the reflection coefficient; α and t are the absorption coefficient and thickness of the active photosensitive layer of the photodiode PD, respectively; h is Planck's constant; and c is the speed of light in a vacuum.

[0078] By adjusting the gate voltage V G3 , so that the third thin film transistor TFT3 is in the on state. At this time, the first dual-gate thin film transistor TFT1 is also in the on state. The first dual-gate thin film transistor TFT1 and the photodiode PD are on the same branch, so the currents flowing through them are equal. The current expressions of the two are as follows:

[0079] I DS1 =I PD =I dark +I photo

[0080] Among them, I dark is the dark state current of the photodiode PD; when the photocurrent Iphoto generated by the photodiode PD under light conditions flows to the drain of the first dual-gate thin film transistor TFT1, a sensing voltage V DS1 , the sensing voltage V DS1 Acts on the second dual-gate thin film transistor TFT2. For the first dual-gate thin film transistor TFT1 using a diode connection, its drain voltage (sensing voltage V DS1 ) and the bottom gate voltage V BG1 are equal, and the two expressions are as follows:

[0081] V DS1 =V BG1

[0082] When the first dual-gate thin film transistor TFT1 operates in the subthreshold region, the source-drain current I of the first dual-gate thin film transistor TFT1 can be obtained according to the current expression of the transistor subthreshold region. DS1 The expression is as follows:

[0083]

[0084] Among them, I D01 It is in V BG1 =V TH1 And V DS1 >>kT / q, the source-drain current of the first dual-gate thin film transistor TFT1; V TH1 is the threshold voltage of the first dual-gate thin film transistor TFT1.

[0085] By simplifying the above two formulas, we can get:

[0086]

[0087] The drain voltage of the first dual-gate thin film transistor TFT1 is derived as the sensing voltage V DS1 The expression is as follows:

[0088]

[0089] From the above derivation results, it can be seen that the drain voltage of the first dual-gate thin film transistor TFT1 (sensing voltage V DS1 ) is logarithmically related to light intensity.

[0090] By adjusting the top gate voltage V TG2 The size makes the second dual-gate thin film transistor TFT2 operate in the subthreshold region. At this time, the signal output by the source of the second dual-gate thin film transistor TFT2 has a quasi-linear relationship with the instantaneous light intensity.

[0091] The first working state enables each pixel unit to be accessed and read at any time, that is, the active pixel circuit can perform random reading, which is suitable for fast imaging; and because the output signal has a quasi-linear relationship with the instantaneous light intensity, the output signal changes more significantly with the light intensity under low light intensity, so the active pixel circuit has higher sensitivity and a wider dynamic response range.

[0092] The second working state, integral reading:

[0093] See also Figure 8 As shown, the first power supply V DD1 The photodiode PD is forward biased and can generate a photocurrent Iphoto under light conditions.

[0094] When the third thin film transistor TFT3 is in the off state, the first double-gate thin film transistor TFT1 is also in the off state. Therefore, the photogenerated charge generated by the photodiode PD under light conditions will not flow to the first double-gate thin film transistor TFT1, but only to the second double-gate thin film transistor TFT2, and the photogenerated charge will be stored in the parasitic capacitance of the second double-gate thin film transistor TFT2; control the second power supply V DD2 , so that the second dual-gate thin film transistor TFT2 is in the off state, at this time the photogenerated charge will continue to accumulate in the parasitic capacitor; control the second power supply V DD2 , so that the second dual-gate thin film transistor TFT2 is in the on state, at which time the photogenerated charge will flow out of the parasitic capacitor and release to generate a signal. The second working state realizes that the active pixel circuit has an integration-reading working mode similar to the passive pixel circuit.

[0095] The third working state, random reading and integral reading:

[0096] See also Figure 9 As shown, for each row in the array, the second dual-gate thin film transistor TFT2 and the third thin film transistor TFT3 are controlled to be in the off state; when executing the first working state (random reading), the second dual-gate thin film transistor TFT2 and the third thin film transistor TFT3 are controlled to be in the on state; when the random reading is completed, the second dual-gate thin film transistor TFT2 and the third thin film transistor TFT3 are controlled to be in the off state again to execute the integration mode. At this time, other rows in the array are still executing random reading and the radiation is still being exposed, while the rows that have completed random reading can execute the integration mode to store the radiation information in the parasitic capacitor; when all rows in the array have completed random reading, the radiation is turned off, and the second dual-gate thin film transistor TFT2 of each row in the array is controlled to be in the on state row by row, so that the radiation information stored in the parasitic capacitor is released for reading.

[0097] When the amplifier circuit is connected to the active pixel unit, the third thin film transistor TFT3 works as a switch tube. By regulating the third thin film transistor TFT3, the on or off state of the first double-gate thin film transistor TFT1 is controlled, and the on or off state of the second double-gate thin film transistor TFT2 is controlled through the peripheral circuit, so that the 3T1D active pixel circuit can operate in different working modes, thereby improving the utilization rate of radiation; and the drain voltage of the first double-gate thin film transistor TFT1 (sensing voltage V DS1) is logarithmically related to the incident light intensity, which can effectively widen the dynamic response range of the pixel circuit; and the second dual-gate thin-film transistor TFT2 acts as an amplifier to improve the sensitivity of the 3T1D active pixel circuit under weak light conditions; therefore, in Examples 6 and 7, after connecting the amplifier circuit to the active pixel unit, the detection lower limit can be lowered, thereby expanding the dynamic response range.

[0098] Example 8

[0099] Connect the first embodiment with multiple columns of passive pixel units to form Figure 10 The 3T passive pixel amplifier circuit shown in Figure 11 As shown, each passive pixel unit includes a photodiode PD and a transistor TFT, and the transistor TFT is connected to the amplifier circuit 1.

[0100] The passive pixel units in each column (Pixel 1.1, Pixel 2.1, Pixel m.1, Pixel 1.2, Pixel 2.2, Pixel m.2, ...) are connected in series so that multiple passive pixel units can be connected to only one amplifier circuit. This means that multiple passive pixel units can share one amplifier circuit, so that only one switching thin film transistor ( Figure 11 The transistor TFT in the circuit greatly improves the pixel fill rate. At the same time, the amplifier circuit 1 is applied to the outside of the passive pixel unit. That is, when the first row is turned on and the other rows are turned off, the amplifier circuit 1 and the passive pixel units in the first row form an active pixel. When the second row is turned on and the other rows are turned off, the amplifier circuit 1 and the passive pixel units in the second row form an active pixel. Through this mode of sharing the same amplifier circuit, the fill rate can be improved while maintaining the high sensitivity and wide dynamic range characteristics of the active pixel, that is, the high sensitivity and wide dynamic range characteristics of the 3T amplifier circuit are retained.

[0101] Therefore, the amplifier circuit disclosed in the present application can be applied to both active pixel and passive pixel scenarios, that is, the amplifier circuit can be connected to an active pixel unit or a passive pixel unit.

[0102] When the amplifier circuit is used in an active pixel unit, it can achieve high gain, high radiation utilization, and multiple operating modes, so that it has the advantages of signal amplification of traditional active pixel circuits and solves the problem of low radiation utilization of traditional active pixel circuits.

[0103] When this amplifier circuit is used in passive pixels, it can achieve high gain and high resolution, so that it has the advantages of signal amplification of traditional active pixel circuits, and solves the problems of low radiation signal-to-noise ratio and inability to detect weak signals in traditional passive pixel circuits.

[0104] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An amplifier circuit for an X-ray flat panel detector, characterized in that: include: a first transistor, a second transistor, and a third transistor; The drain of the first transistor is connected to the second transistor; The source of the first transistor is grounded; The first transistor is connected to the third transistor; The drain of the first transistor is connected to the active pixel unit or the passive pixel unit.

2. The amplifier circuit for an X-ray flat panel detector according to claim 1, characterized in that: The first transistor is a dual-gate thin film transistor; the second transistor is a dual-gate thin film transistor; and the third transistor is a single-gate thin film transistor or a dual-gate thin film transistor.

3. The amplifier circuit for an X-ray flat panel detector according to claim 2, characterized in that: The drain of the second transistor is connected to a second power supply; The source of the second transistor is a signal output terminal.

4. The amplifier circuit for an X-ray flat panel detector according to claim 2, characterized in that: The drain of the second transistor is connected to the source of the first transistor; The source of the second transistor is a signal output terminal.

5. The amplifier circuit for an X-ray flat panel detector according to claim 2, characterized in that: The drain of the first transistor is connected to the top gate or the bottom gate of the first transistor through the third transistor.

6. The amplifier circuit for an X-ray flat panel detector according to claim 2, characterized in that: The drain of the first transistor is connected to the top gate or the bottom gate of the second transistor.

7. The amplifier circuit for an X-ray flat panel detector according to claim 2, characterized in that: The active pixel unit includes a photoelectric device, and the photoelectric device is connected to the drain of the first transistor and a first power source.

8. The amplifier circuit for an X-ray flat panel detector according to claim 7, characterized in that: The photoelectric device is a photodiode; The first power supply is connected to the cathode of the photodiode; The anode of the photodiode is connected to the drain of the first transistor; An anode of the photodiode is connected to a top gate or a bottom gate of the second transistor.

9. The amplifier circuit for an X-ray flat panel detector according to claim 7, characterized in that: The optoelectronic device is a photoelectric device made of a photoconductive material.

10. The amplifier circuit for an X-ray flat panel detector according to claim 2, characterized in that: The passive pixel unit includes a photodiode and a fourth transistor; The cathode of the photodiode is connected to the drain of the first transistor through the fourth transistor.

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