High-performance 3T circuit capable of quickly entering subthreshold interval to work

Abstract

The invention discloses a high-performance 3T circuit capable of quickly entering a sub-threshold interval to work, and relates to the technical field of thin film transistors, the high-performance 3T circuit is characterized in that a drain electrode and a top grid electrode of a double-grid thin film transistor and a grid electrode of a single-grid thin film transistor I are connected to a signal input end, and a source electrode of the double-grid thin film transistor is grounded; the drain electrode of the first single-gate thin film transistor is connected with bias voltage, the source electrode of the first single-gate thin film transistor is connected with the drain electrode of the second single-gate thin film transistor, the grid electrode of the second single-gate thin film transistor serves as a reading end, the source electrode of the second single-gate thin film transistor serves as a data end, and the bottom grid electrode of the double-gate thin film transistor is connected with regulation voltage; through the synergistic effect of the double-gate thin film transistor and the first single-gate thin film transistor, the circuit can rapidly enter a sub-threshold interval to work, rapid switching of an amplification state is achieved, the circuit sensitivity is remarkably improved under the condition of weak light, the dynamic response range is widened, the X-ray utilization rate is improved, meanwhile, the technology is simplified, large-area preparation is facilitated, and the cost is reduced. The technical problem that the performance of an existing APS amplification circuit cannot be rapidly improved is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thin film transistors, and in particular to a high-performance 3T circuit capable of quickly working in a sub-threshold interval. BACKGROUND

[0002] With the wide application of flat panel detectors in X-ray imaging, the core circuit design puts forward higher requirements for imaging sensitivity, signal-to-noise ratio and dynamic response speed. The traditional passive pixel circuit (PPS) is widely used due to its simple structure and mature process, but it lacks on-chip amplification function, resulting in a decrease in image signal-to-noise ratio and image quality under low-dose X-ray conditions, thereby affecting the accuracy of diagnosis and failing to meet the clinical demand for high sensitivity and low-dose imaging.

[0003] To improve the above-mentioned deficiencies, an active pixel circuit (APS) is proposed and applied to some new detectors. The APS circuit introduces an active device as an amplification unit, which can achieve higher gain and better signal-to-noise ratio, and the imaging performance is significantly improved. However, the current common APS circuit still has several limitations: its dynamic range is generally narrow, and it is difficult to maintain stable output in a wide working interval of high dose and low dose; at the same time, the utilization rate of rays is insufficient, and most of the working time is in the empty exposure state, resulting in low detection efficiency.

[0004] To solve the above problems, the prior art attempts to use a dual-gated thin film transistor (DG-TFT) to construct an APS circuit with high sensitivity, high gain and wide dynamic range. The dual-gate structure can realize more flexible working mode by adjusting the upper and lower gate voltages, thereby improving the dynamic response of the circuit. However, the process of DG-TFT is not mature yet, the preparation process is complex and the cost is high, and the device consistency and stability are insufficient, which makes it difficult to meet the demand of large-area preparation and large-scale application. This limits the promotion of this scheme in actual products.

[0005] Therefore, how to construct a high-performance amplification circuit capable of quickly working in a sub-threshold interval under the premise of process simplification and large-area preparation has become a research focus in the field.

[0006] In summary, it is found that the prior art at least has the following technical problems: The existing APS amplification circuit cannot quickly work in a sub-threshold interval, resulting in the technical problem that the performance of the amplification circuit cannot be quickly improved. SUMMARY

[0007] The application aims to provide a high-performance 3T circuit capable of quickly entering a sub-threshold interval to solve the technical problem that the existing APS amplification circuit cannot quickly enter a sub-threshold interval, resulting in the performance of the amplification circuit being unable to be quickly improved.

[0008] The preferred technical solutions in the various technical solutions provided by the application can produce the technical effects described below.

[0009] To solve the above technical problems, the application provides the following technical solutions. The application provides a high-performance 3T circuit capable of quickly entering a sub-threshold interval, which comprises a double-gate thin film transistor, two single-gate thin film transistors, namely a double-gate thin film transistor, a single-gate thin film transistor one and a single-gate thin film transistor two; the drain and top gate of the double-gate thin film transistor and the gate of the single-gate thin film transistor one are connected to a signal input end, the source of the double-gate thin film transistor is grounded, the drain of the single-gate thin film transistor one is connected to a bias voltage, the source of the single-gate thin film transistor one and the drain of the single-gate thin film transistor two are connected, the gate of the single-gate thin film transistor two serves as a reading end and the source serves as a data end, the bottom gate of the double-gate thin film transistor is connected to a control voltage, the working state of the transistor is quickly changed by adjusting the voltage, thereby forming a 3T amplification circuit that promotes the double-gate thin film transistor and the single-gate thin film transistor one to quickly enter a sub-threshold interval; the output voltage of the double-gate thin film transistor is controlled by the input signal of the signal input end, which is used to widen the dynamic response range of the 3T amplification circuit; the single-gate thin film transistor one serves as an amplifier, which is used to improve the sensitivity of the 3T amplification circuit under weak light conditions and expand the dynamic response range of the 3T amplification circuit by reducing the detection lower limit of the input components of the signal input end; the single-gate thin film transistor two only serves as a switching device, which is used to control the reading of the 3T amplification circuit.

[0010] In one embodiment, the input current of the double-gate thin film transistor is adjusted to make the double-gate thin film transistor work in a sub-threshold region, which is used to widen the dynamic response range of the pixel circuit and realize the logarithmic conversion of the output voltage of the double-gate thin film transistor by the photoelectric current entering from the signal input end; The logarithmic conversion relationship between the photoelectric current input by the single-gate thin film transistor one and the output voltage is: V ds1 =V TH1 + ln( )

[0011] Wherein, V ds1 represents the output voltage of the double-gate thin film transistor, V TH1represents the threshold voltage of the double-gate thin film transistor, I signal represents the photo-current signal entering from the signal input end, represents the input current of the double-gate thin film transistor, represents the sub-threshold slope factor of the double-gate thin film transistor, represents the thermal voltage.

[0012] In one embodiment, the single-gate thin film transistor one is made to work in the sub-threshold region by adjusting the size of the input current of the single-gate thin film transistor one, so as to exhibit exponential amplification performance; the relationship between the output current of the single-gate thin film transistor one and the output voltage of the double-gate thin film transistor is as follows: I out =I DS2 ·exp[ ]

[0013] wherein, I out represents the output current of the single-gate thin film transistor one, I DS2 represents the input current of the single-gate thin film transistor one, V ds1 represents the output voltage of the double-gate thin film transistor, V TH2 represents the threshold voltage of the single-gate thin film transistor one, represents the sub-threshold slope factor of the single-gate thin film transistor one, and q represents the electronic charge amount.

[0014] In one embodiment, the drain of the single-gate thin film transistor one is connected to the bias voltage of the source of the double-gate thin film transistor, so that the drain of the single-gate thin film transistor two serves as the output end.

[0015] In one embodiment, a photo-diode is further included, which forms a 3T active pixel circuit with the 3T amplification circuit; the anode of the photo-diode is connected to the signal input end, for forming a sensing part of the 3T active pixel circuit; the cathode of the photo-diode and the drain of the single-gate thin film transistor one are respectively connected to bias voltages VDD1 and VDD2; by controlling the double-gate thin film transistor and the single-gate thin film transistor one to work in the sub-threshold region, the output voltage of the double-gate thin film transistor is made to have a logarithmic relationship with the incident light intensity of the photo-diode, for widening the dynamic response range of the 3T active pixel circuit, making the single-gate thin film transistor one serve as an in-pixel amplifier, and improving the sensitivity of the 3T active pixel circuit under weak light conditions of the photo-diode, i.e. expanding the dynamic response range of the 3T active pixel circuit by lowering the lower limit of the detection of the photo-diode; the single-gate thin film transistor two serves as a switch transistor, for controlling the readout of the 3T active pixel circuit.

[0016] In one embodiment, a photoconductive unit made of a photoconductive material is also included, and the photoconductive unit is connected to the 3T amplification circuit to form a 3T direct detection type circuit; the front surface of the contact electrode of the photoconductive unit is used to directly sense the required detection material, and the back surface of the contact electrode of the photoconductive unit is connected to the signal input end to form a sensing part of the 3T direct detection type circuit; by controlling the double-gate thin film transistor and the single-gate thin film transistor to work in a sub-threshold interval, the output voltage of the double-gate thin film transistor has a logarithmic relationship with the incident light intensity of the photoconductive unit, which is used to widen the dynamic response range of the 3T direct detection type circuit, and the single-gate thin film transistor is used as an in-pixel amplifier to improve the sensitivity of the 3T direct detection type circuit under weak light conditions of the photodiode, that is, the dynamic response range of the 3T direct detection type circuit is expanded by lowering the lower limit of detection of the photodiode; the single-gate thin film transistor is used as a switch transistor to control the readout of the 3T direct detection type circuit.

[0017] In one embodiment, the drain of the single-gate thin film transistor is connected to a bias voltage, and the source of the double-gate thin film transistor is connected to the bias voltage, so that the drain of the single-gate thin film transistor is used as an output end.

[0018] In one embodiment, a plurality of passive pixel units are also included; a plurality of the passive pixel units are connected in parallel to the signal input end of the 3T amplification circuit to form a 3T passive pixel amplification circuit; the pixel amplification is realized by selecting the passive pixel unit to be read out in the 3T passive pixel amplification circuit through a row selection function, and the 3T amplification circuit is used as an external amplification circuit, so that only one switch thin film transistor is required in each of the plurality of passive pixel units, which is used to improve the pixel fill factor of the 3T passive pixel amplification circuit, and the 3T amplification circuit has high sensitivity and wide dynamic range.

[0019] In one embodiment, the passive pixel unit includes a photodiode and a switch thin film transistor; the anode of the photodiode is connected to the drain of the switch thin film transistor, and the source of the switch thin film transistor is connected to the signal input end.

[0020] In one embodiment, a plurality of the 3T amplification circuits are arranged in an array, and the plurality of 3T amplification circuits are respectively connected to the 3T passive pixel amplification circuit, and a plurality of columns of the 3T passive pixel amplification circuit form a passive pixel matrix to improve the detection resolution.

[0021] The present application aims at the technical problem that the existing APS amplification circuit cannot quickly enter the sub-threshold interval to work, resulting in the performance of the amplification circuit cannot be quickly improved, by introducing a combination structure of a double-gate thin film transistor and two single-gate thin film transistors in the 3T amplification circuit, a high-performance circuit capable of quickly entering the sub-threshold interval to work is formed, and has the following beneficial effects:

[0022] (1) Quickly enter the sub-threshold interval to improve circuit performance; by regulating the bottom gate voltage of the double-gate thin film transistor, the working state of the transistor is quickly changed by adjusting the voltage, so that the double-gate thin film transistor and the single-gate thin film transistor are quickly entered into the sub-threshold interval, thereby accelerating the response speed of the amplification circuit, solving the problem that the existing APS amplification circuit cannot quickly enter the sub-threshold interval.

[0023] (2) Achieve high gain and high sensitivity; the single-gate thin film transistor one serves as an amplifier device, which can improve the signal output amplitude of the circuit under weak light and low dose X-ray conditions, reduce the lower limit of input detection, effectively improve the sensitivity and signal-to-noise ratio, and meet the low dose imaging demand.

[0024] (3) Widening the dynamic response range; under the dual action of signal input and regulating voltage, the output voltage of the double-gate thin film transistor can cover a wider dynamic interval, thereby expanding the dynamic response range of the circuit and improving the narrow dynamic range of the traditional APS circuit.

[0025] (4) Improving the utilization rate of X-rays and imaging efficiency; by quickly switching the working state of the circuit, more working time is in the effective detection stage, reducing the empty exposure time, improving the utilization rate of X-rays, and realizing more efficient imaging.

[0026] (5) Process feasibility and large-area preparation advantage; the present application only uses the combination of single-gate and double-gate thin film transistors, avoiding the design of DG-TFT which completely relies on complex process, which not only guarantees the device performance, but also takes into account the large-area preparation and cost control, which is conducive to popularization and application.

[0027] In summary, the present application not only solves the technical problems of passive pixel circuit lacking amplification function, narrow dynamic range of APS circuit and low utilization rate of X-rays, but also significantly improves the sensitivity, dynamic range, imaging efficiency and process feasibility. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0029] Figure 1 is a structural schematic diagram of a 3T amplification circuit of the first embodiment of the present application; Figure 2 is a structural schematic diagram of a 3T amplification circuit of the first embodiment of the present application; Figure 3 is a structural schematic diagram of a 3T active pixel circuit of the second embodiment of the present application; Figure 4 is a structural schematic diagram of a 3T active pixel circuit of the second embodiment of the present application; Figure 5 is a structural schematic diagram of a 3T direct detection type circuit of the third embodiment of the present application; Figure 6 is a structural schematic diagram of a 3T direct detection type circuit of the third embodiment of the present application; Figure 7 is a structural schematic diagram of a 3T passive pixel amplification circuit of the fourth embodiment of the present application; Figure 8 is a structural schematic diagram of a passive pixel matrix of the fifth embodiment of the present application.

[0030] In the drawings, the reference signs are as follows: 1, double-gate thin film transistor; 11, signal input end; 12, control voltage; 2, single-gate thin film transistor one; 3, single-gate thin film transistor two; 31, read end; 32, data end; 33, output end; 4, 3T amplification circuit; 5, 3T active pixel circuit; 6, 3T direct detection type circuit; 61, photoconductive unit; 7, 3T passive pixel amplification circuit; 71, passive pixel unit; 72, switch thin film transistor; 8, passive pixel matrix; 9, photodiode. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.

[0032] This specific implementation provides a high-performance 3T circuit that rapidly enters the subthreshold operating range, comprising a dual-gate thin-film transistor (TFT) and two single-gate TFTs. The drain and top gate of the dual-gate TFT are connected to the gate of the first single-gate TFT at the signal input terminal. The source of the dual-gate TFT is grounded. The drain of the first single-gate TFT is connected to a bias voltage, and its source is connected to the drain of the second single-gate TFT. The gate of the second single-gate TFT serves as the readout terminal, and its source as the data terminal. The bottom gate of the dual-gate TFT is connected to a control voltage. Through the synergistic effect of the dual-gate TFT and the first single-gate TFT, this circuit can rapidly enter the subthreshold operating range, achieving rapid switching between amplification states. It significantly improves circuit sensitivity under low-light conditions, broadens the dynamic response range, and enhances X-ray utilization. Simultaneously, the simplified process facilitates large-area fabrication. This effectively solves the technical problem that existing APS amplifier circuits cannot rapidly enter the subthreshold operating range, thus hindering rapid performance improvement.

[0033] The first implementation of a high-performance 3T circuit, for example Figure 1 As shown, it includes a dual-gate thin-film transistor 1 and two single-gate thin-film transistors, namely dual-gate thin-film transistor 1, single-gate thin-film transistor 2, and single-gate thin-film transistor 3. The drain and top gate of dual-gate thin-film transistor 1 and the gate of single-gate thin-film transistor 2 are connected to the signal input terminal 11. The source of dual-gate thin-film transistor 1 is grounded. The drain of single-gate thin-film transistor 2 is connected to the bias voltage VDD. The source of single-gate thin-film transistor 2 is connected to the drain of single-gate thin-film transistor 3. The gate of single-gate thin-film transistor 3 serves as the read terminal 31, and the source serves as the data terminal 32. The bottom gate of dual-gate thin-film transistor 1 is connected to the control voltage 12. By adjusting... The voltage rapidly changes the operating state of the transistor, forming a 3T amplifier circuit 4 that causes the dual-gate thin-film transistor 1 and the single-gate thin-film transistor 2 to quickly enter the subthreshold region. The output voltage of the dual-gate thin-film transistor 1 is controlled by the input signal at the signal input terminal 11 to broaden the dynamic response range of the 3T amplifier circuit 4. The single-gate thin-film transistor 2 acts as an amplifier to improve the sensitivity of the 3T amplifier circuit 4 under low light conditions and expands the dynamic response range of the 3T amplifier circuit 4 by lowering the detection limit of the input components at the signal input terminal 11. The single-gate thin-film transistor 3 acts only as a switching device to control the readout of the 3T amplifier circuit 4.

[0034] Specifically, this invention addresses the technical problem that existing APS amplifier circuits cannot quickly enter the subthreshold range, thus hindering rapid performance improvement. By introducing a combination structure of a dual-gate thin-film transistor 1 and two single-gate thin-film transistors into the 3T amplifier circuit 4, a high-performance circuit capable of quickly entering the subthreshold range is formed, possessing several technical advantages: rapid entry into the subthreshold range, improving circuit performance; and by adjusting the bottom gate voltage of the dual-gate thin-film transistor 1, the operating state of the transistor can be rapidly changed, prompting both the dual-gate thin-film transistor 1 and the single-gate thin-film transistor 2 to quickly enter the subthreshold range, thereby accelerating the response speed of the amplifier circuit and solving the problem that existing APS amplifier circuits cannot quickly enter the subthreshold range.

[0035] Achieving high gain and high sensitivity; the single-gate thin-film transistor-2, as an amplifying device, can improve the signal output amplitude of the circuit under weak light and low-dose X-ray conditions, reduce the lower limit of the input detection, effectively improve sensitivity and signal-to-noise ratio, and meet the requirements of low-dose imaging.

[0036] The dynamic response range is widened; under the dual action of the signal input terminal 11 and the control voltage 12, the output voltage of the dual-gate thin film transistor 1 can cover a wider dynamic range, thereby expanding the dynamic response range of the circuit and improving the shortcomings of the narrow dynamic range of traditional APS circuits.

[0037] It improves X-ray utilization and imaging efficiency; by rapidly switching the circuit's operating state, more working time is spent in the effective detection phase, reducing air exposure time, improving X-ray utilization, and achieving more efficient imaging.

[0038] Advantages of process feasibility and large-area fabrication: This invention uses only a combination of single-gate and dual-gate thin-film transistors 1, avoiding the DG-TFT design that relies entirely on complex processes. This ensures device performance while also taking into account large-area fabrication feasibility and cost control, which is conducive to widespread application.

[0039] In summary, this invention not only solves the technical problems of passive pixel circuits lacking amplification function, APS circuits having narrow dynamic range and low X-ray utilization, but also achieves significant improvements in sensitivity, dynamic range, imaging efficiency and process feasibility.

[0040] Among them, such as Figure 2 As shown, the bias voltage connected to the drain of the single-gate thin-film transistor 2 is connected to the source of the dual-gate thin-film transistor 1, making the drain of the single-gate thin-film transistor 3 the output terminal 33.

[0041] In application, by applying input voltages of different amplitudes at the signal input terminal 11, the dual-gate thin-film transistor 1 can quickly enter the subthreshold range under the coordinated control of the top and bottom gates. At the same time, the single-gate thin-film transistor 2 acts as an amplification device, effectively amplifying the input weak light signal, so that the circuit still has high sensitivity and signal-to-noise ratio under low-dose X-ray conditions, ensuring the clarity and stability of the image. The single-gate thin-film transistor 3 acts as a readout switch, turning on only when output is needed, thereby reducing the power consumption and invalid response of the circuit. Through this circuit structure, the amplification circuit as a whole can quickly switch to a high-sensitivity state under weak light conditions, widening the dynamic response range and solving the problem that existing APS circuits are difficult to quickly enter the subthreshold range and have slow amplification performance response.

[0042] Furthermore, it can be extended to arrayed pixel circuits, applying high-performance 3T circuits to large-area flat panel detector arrays, using row and column gating to control the switching of single-gate thin-film transistors, thereby achieving large-scale parallel detection and fast readout.

[0043] In addition, a dynamic adjustment module can be introduced into the bottom gate control voltage 12 section of the dual-gate thin-film transistor 1 to optimize the bias level in real time according to the incident X-ray dose intensity, so as to further improve the detection sensitivity of the circuit under ultra-low dose and reduce the overall energy consumption by integrating a low-power drive circuit.

[0044] As one alternative implementation method: Regarding the control principle and function of the aforementioned dual-gate thin-film transistor 1, this implementation is as follows: Figure 1 As shown, by adjusting the physical dimensions and input current of the dual-gate thin-film transistor 1, it is made to operate in the subthreshold region, thereby widening the dynamic response range of the pixel circuit and realizing the logarithmic conversion of the photocurrent entering from the signal input terminal 11 to the output voltage of the dual-gate thin-film transistor 1. Specifically, the logarithmic conversion relationship between the photocurrent input to the single-gate thin-film transistor 2 and the output voltage is as follows: V ds1 =V TH1 + ln( )

[0045] Among them, V ds1 V represents the output voltage of the dual-gate thin-film transistor 1. TH1 I represents the threshold voltage of the dual-gate thin-film transistor 1. signal This indicates the photocurrent signal entering from signal input terminal 11. This represents the input current of the dual-gate thin-film transistor 1. The subthreshold slope factor represents the gate voltage's ability to control the current in the dual-gate thin-film transistor 1. represents the thermoelectric voltage (about 26 mV at room temperature), reflecting the influence of carrier thermal motion on the characteristics of the device.

[0046] Specifically, the thermoelectric voltage expression is V T = KT / q (K is the Boltzmann constant, q is the electronic charge, and T is the temperature).

[0047] In the application, the double-gate thin film transistor 1 is arranged at the front end of the 3T amplification circuit 4 as a signal conditioning and voltage-current conversion module for an input signal. For specific application parameter scenarios, the channel length, gate dielectric thickness, and bias voltage can be customized to make the photocurrent input under weak light conditions more easily converted into a stable output voltage signal, thereby realizing accurate control and digitization of the input photocurrent by the signal terminal ST.

[0048] The structure can effectively improve the signal-to-noise ratio, reduce readout noise, and improve the dynamic response range under the low-dose working state of the X-ray flat panel detector, solving the problem of insufficient gain of the traditional APS circuit under low dose.

[0049] In addition, the channel width-to-length ratio is adjusted according to different detector pixel areas, and various high-k dielectric materials are used to optimize the gate dielectric to further reduce the leakage current and enhance the response capability of the input terminal to weak signals.

[0050] The control principle and function of the single-gate thin film transistor 1 are as shown in the embodiment of the present application. Figure 1 By adjusting the physical size of the single-gate thin film transistor 1 and the size of the input current, the single-gate thin film transistor 1 works in the subthreshold region and exhibits exponential amplification performance.

[0051] Specifically, the relationship between the output current of the single-gate thin film transistor 1 and the output voltage of the double-gate thin film transistor 1 is as follows: I out = I DS2 · exp[ ]

[0052] Where I out represents the output current of the single-gate thin film transistor 1, I DS2 represents the input current of the single-gate thin film transistor 1, V ds1 represents the output voltage of the double-gate thin film transistor 1, V TH2 represents the threshold voltage of the single-gate thin film transistor 1, represents the subthreshold slope factor of the single-gate thin film transistor 1, and q represents the electronic charge.

[0053] In the application, the single-gate thin film transistor 2 is arranged in the middle stage of the 3T amplification circuit 4 as an active amplifier device, coupled with the signal input end 11 by connecting the bias voltage VDD, and the output signal of the double-gate thin film transistor 1 is amplified twice and the current output characteristic is adjusted.

[0054] In actual operation, for specific application parameter scenarios, gain optimization can be realized by adjusting physical parameters such as threshold voltage, mobility and channel parameters, to ensure stable output current in a large dynamic range; the structure significantly improves the detection sensitivity and signal-to-noise ratio under weak light and low dose conditions, expands the dynamic response range, and effectively solves the problems of complex process and unstable gain of the existing DG-TFT circuit.

[0055] The second embodiment of the high-performance 3T circuit is shown in Figure 3 The difference between this embodiment and the first embodiment is that it further includes a photodiode 9, the photodiode 9 is connected to the 3T amplification circuit 4 to form a 3T active pixel circuit 5; the anode of the photodiode 9 is connected to the signal input end 11 to form the sensing part of the 3T active pixel circuit 5; the cathode of the photodiode 9 and the drain of the single-gate thin film transistor 2 are connected to bias voltages VDD1 and VDD2, respectively; by controlling the double-gate thin film transistor 1 and the single-gate thin film transistor 2 to work in the sub-threshold interval, the output voltage of the double-gate thin film transistor 1 has a logarithmic relationship with the incident light intensity of the photodiode 9, which is used to widen the dynamic response range of the 3T active pixel circuit 5, make the single-gate thin film transistor 2 as an in-pixel amplifier, and improve the sensitivity of the 3T active pixel circuit 5 under weak light conditions of the photodiode 9, that is, by reducing the lower limit of the photodiode 9, the dynamic response range of the 3T active pixel circuit 5 is expanded; the single-gate thin film transistor 3 is used as a switch transistor to control the readout of the 3T active pixel circuit 5.

[0056] As shown in Figure 4 The drain of the single-gate thin film transistor 2 is connected to the source of the double-gate thin film transistor 1, and the drain of the single-gate thin film transistor 3 is used as the output end 33.

[0057] In application, the photodiode 9 directly serves as the sensing part of the signal input end 11, when the incident light or X-ray reaches the photodiode 9, the generated charge signal is rapidly amplified through the sub-threshold working interval of the double-gate thin film transistor 1 and the single-gate thin film transistor 1, so that the output voltage is logarithmically related to the incident light intensity, realizing wide dynamic range response; in the weak light condition, the single-gate thin film transistor 1 further improves the amplification capability of the weak signal, reduces the detection lower limit of the photodiode 9, and ensures high sensitivity imaging under low dose condition; the single-gate thin film transistor 2 serves as a switch transistor, realizing stable readout, and solving the problems of insufficient sensitivity and limited dynamic range of the traditional APS circuit in the weak light condition.

[0058] Further, in large-scale imaging of the detector, each pixel unit is formed by the photodiode 9 combined with the 3T circuit, realizing row-by-row readout and column amplification; and in the material selection of the photodiode 9, high-sensitivity amorphous selenium or perovskite material can be used to improve the response capability to low-energy X-ray, thereby further improving the performance of weak dose medical imaging.

[0059] A third embodiment of the high-performance 3T circuit is shown in Figure 5 The difference between this embodiment and the first embodiment is that it further includes a photoconductive unit 61 made of photoconductive material, the photoconductive unit 61 is connected to the 3T amplification circuit 4 to form a 3T direct detection type circuit 6; the front surface of the contact electrode of the photoconductive unit 61 is used to directly sense the required detection material, and the back surface of the contact electrode of the photoconductive unit 61 is connected with the signal input end 11 to form the sensing part of the 3T direct detection type circuit 6; by controlling the double-gate thin film transistor 1 and the single-gate thin film transistor 1 to work in the sub-threshold interval, the output voltage of the double-gate thin film transistor 1 is logarithmically related to the incident light intensity of the photoconductive unit 61, which is used to widen the dynamic response range of the 3T direct detection type circuit 6; the single-gate thin film transistor 1 serves as an in-pixel amplifier to improve the sensitivity of the 3T direct detection type circuit 6 in the weak light condition of the photodiode 9, that is, the dynamic response range of the 3T direct detection type circuit 6 is expanded by reducing the detection lower limit of the photodiode 9; and the single-gate thin film transistor 2 serves as a switch transistor to control the readout of the 3T direct detection type circuit 6.

[0060] As shown in Figure 6 The drain of the single-gate thin film transistor 2 is connected with the source of the double-gate thin film transistor 1 through a bias voltage, and the drain of the single-gate thin film transistor 3 serves as the output end 33.

[0061] In application, the photoconductive unit 61 directly contacts the target material to be detected through the front electrode to realize direct detection of the incident light or X-ray, and the generated electric signal is transmitted to the 3T amplification circuit 4 through the back electrode.

[0062] The double-gate thin film transistor 1 and the single-gate thin film transistor one 2 work together in the subthreshold interval, so that the output voltage is logarithmically responsive to the incident light intensity, and the dynamic range is expanded, and the single-gate thin film transistor two 3 is used as an amplifier to improve the signal amplitude, so that the circuit still maintains high sensitivity imaging under low dose and weak light conditions; the single-gate thin film transistor two 3 is used as a switch transistor to ensure the timing controllability of the output, and solves the problems of slow response speed and loss of weak signal of the existing direct detection type circuit.

[0063] Further, the photoconductive material adopts a semiconductor such as CdZnTe, PbI2, GaAs, etc., to adapt to the X-ray or spectral detection requirements of different wavebands; and a micro-nano structure is arranged on the surface of the photoconductive unit 61 to improve the absorption efficiency of the incident light, thereby further improving the response speed and detection sensitivity.

[0064] A fourth embodiment of the high-performance 3T circuit is shown in Figure 7 The difference between this embodiment and the first embodiment is that it further includes a plurality of passive pixel units 71; the plurality of passive pixel units 71 are connected in parallel to the signal input end 11 of the 3T amplification circuit 4 to form a 3T passive pixel amplification circuit 7; the pixel amplification is realized by selecting the passive pixel unit 71 to be read out in the 3T passive pixel amplification circuit 7 through the row selection function, and the 3T amplification circuit 4 is used as an external amplifier, so that only one switching thin film transistor 72 needs to be reserved in the plurality of passive pixel units 71, which improves the pixel fill rate of the 3T passive pixel amplification circuit 7, and also has the high sensitivity and wide dynamic range performance of the 3T amplification circuit 4.

[0065] Specifically, the passive pixel unit 71 includes a photodiode 9 and a switching thin film transistor 72; the anode of the photodiode 9 is connected to the drain of the switching thin film transistor 72, and the source of the switching thin film transistor 72 is connected to the signal input end 11.

[0066] In application, the plurality of passive pixel units 71 are connected in parallel to the signal input end 11, and the 3T amplification circuit 4 is used as an external amplifier; when a passive pixel unit 71 is selected through the row selection function, the photodiode 9 signal of the pixel unit is transmitted to the 3T amplification circuit 4 for amplification and reading out; through this circuit structure, high sensitivity and wide dynamic range performance can be provided while maintaining high pixel fill rate, effectively solving the problems of no amplification function and insufficient sensitivity of the traditional passive pixel circuit.

[0067] Further, in the amplification and readout mode, a multi-row parallel readout mode is adopted, and the overall readout speed is improved by increasing the column buffer module. Meanwhile, in the passive pixel unit 71, the photodiode 9 with different response wavebands can be selected to realize multi-spectral imaging applications, thereby expanding the application scenarios of the circuit in industrial detection and multi-modal medical imaging.

[0068] The fifth embodiment of the high-performance 3T circuit is shown in FIG. 5. The difference between this embodiment and the first embodiment is that a plurality of 3T amplification circuits 4 are arranged in an array, and each 3T amplification circuit 4 is connected to a 3T passive pixel amplification circuit 7. A plurality of 3T passive pixel amplification circuits 7 form a passive pixel matrix 8 to improve the detection resolution. Figure 8 As shown in FIG. 5, the difference between this embodiment and the first embodiment is that a plurality of 3T amplification circuits 4 are arranged in an array, and each 3T amplification circuit 4 is connected to a 3T passive pixel amplification circuit 7. A plurality of 3T passive pixel amplification circuits 7 form a passive pixel matrix 8 to improve the detection resolution.

[0069] In application, a plurality of 3T amplification circuits 4 are arranged in an array and connected to a plurality of passive pixel amplification circuits to form a large-scale passive pixel matrix 8. The pixel units in the matrix are read out row by row through row-column addressing. The signal of each column is processed by the corresponding 3T amplification circuit 4, thereby significantly improving the sensitivity and dynamic response range while ensuring high resolution. This circuit structure effectively solves the problem of insufficient signal-to-noise ratio of the traditional passive pixel matrix 8 with high resolution, and realizes the unification of high resolution and high-performance imaging.

[0070] Further, the passive pixel matrix 8 is modularized to form a modular pixel matrix structure. A larger area detection panel can be formed by splicing a plurality of arrays to meet the needs of large-size medical imaging or industrial detection. Meanwhile, an intelligent control chip can be introduced to the periphery of the matrix to dynamically adjust the bias voltage and gate voltage to adapt to different doses and different imaging modes.

[0071] The technical features of the above embodiments can be combined in any manner. For brevity, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. A high-performance 3T circuit that rapidly enters the subthreshold operating range, characterized in that, It includes one dual-gate thin-film transistor and two single-gate thin-film transistors, namely, dual-gate thin-film transistor, single-gate thin-film transistor one and single-gate thin-film transistor two; The drain and top gate of the dual-gate thin-film transistor and the gate of the first single-gate thin-film transistor are connected to the signal input terminal. The source of the dual-gate thin-film transistor is grounded. The drain of the first single-gate thin-film transistor is connected to a bias voltage. The source of the first single-gate thin-film transistor is connected to the drain of the second single-gate thin-film transistor. The gate of the second single-gate thin-film transistor is used as the read terminal and the source is used as the data terminal. The bottom gate of the dual-gate thin-film transistor is connected to a control voltage. By adjusting the voltage, the operating state of the transistor is quickly changed, forming a 3T amplifier circuit that causes the dual-gate thin-film transistor and the first single-gate thin-film transistor to quickly enter the subthreshold region. The output voltage of the dual-gate thin-film transistor is controlled by the input signal at the signal input terminal, which is used to broaden the dynamic response range of the 3T amplifier circuit. The single-gate thin-film transistor serves as an amplifier to improve the sensitivity of the 3T amplifier circuit under low-light conditions and expand the dynamic response range of the 3T amplifier circuit by lowering the detection limit of the input components at the signal input terminal. The single-gate thin-film transistor II is used only as a switching device to control the readout of the 3T amplifier circuit.

2. The high-performance 3T circuit according to claim 1, characterized in that, By adjusting the magnitude of the input current of the dual-gate thin-film transistor, the dual-gate thin-film transistor is made to operate in the subthreshold region, which is used to widen the dynamic response range of the pixel circuit and realize the logarithmic conversion of the photocurrent entering from the signal input terminal to the output voltage of the dual-gate thin-film transistor. The logarithmic transformation relationship between the input photocurrent and the output voltage of the single-gate thin-film transistor is as follows: V ds1 =V TH1 + ln( ) Among them, V ds1 V represents the output voltage of the dual-gate thin-film transistor. TH1 I represents the threshold voltage of the dual-gate thin-film transistor. signal This represents the photocurrent signal entering from the signal input terminal. This represents the input current of the dual-gate thin-film transistor. This represents the subthreshold slope factor of the dual-gate thin-film transistor. This represents thermal voltage.

3. The high-performance 3T circuit according to claim 2, characterized in that, By adjusting the magnitude of the input current of the single-gate thin-film transistor, the single-gate thin-film transistor is made to operate in the subthreshold region, exhibiting exponential amplification performance. The relationship between the output current of the single-gate thin-film transistor and the output voltage of the dual-gate thin-film transistor is as follows: I out =I DS2 ·exp[ ] Among them, I out I represents the output current of the single-gate thin-film transistor. DS2 V represents the input current of the single-gate thin-film transistor. ds1 V represents the output voltage of the dual-gate thin-film transistor. TH2 This represents the threshold voltage of the single-gate thin-film transistor. The subthreshold slope factor represents the single-gate thin-film transistor, and q represents the electron charge.

4. The high-performance 3T circuit according to claim 1, characterized in that, The bias voltage connected to the drain of the first single-gate thin-film transistor is grounded with the source of the second double-gate thin-film transistor, so that the drain of the second single-gate thin-film transistor is used as the output terminal.

5. The high-performance 3T circuit according to claim 1, characterized in that, It also includes a photodiode, which is connected to the 3T amplifier circuit to form a 3T active pixel circuit; The anode of the photodiode is connected to the signal input terminal to form the sensing part of the 3T active pixel circuit; The bias voltages connected to the cathode of the photodiode and the drain of the single-gate thin-film transistor are VDD1 and VDD2, respectively. By controlling the dual-gate thin-film transistor and the single-gate thin-film transistor to operate in the subthreshold range, the output voltage of the dual-gate thin-film transistor is logarithmically related to the incident light intensity of the photodiode. This is used to broaden the dynamic response range of the 3T active pixel circuit and to make the single-gate thin-film transistor act as an in-pixel amplifier, thereby improving the sensitivity of the 3T active pixel circuit under low light conditions. In other words, the dynamic response range of the 3T active pixel circuit is expanded by lowering the detection lower limit of the photodiode. The single-gate thin-film transistor II acts as a switching transistor to control the readout of the 3T active pixel circuit.

6. The high-performance 3T circuit according to claim 1, characterized in that, It also includes a photoconductive unit made of photoconductive material, which is connected to the 3T amplifier circuit to form a 3T direct detection circuit; The front side of the contact electrode of the photoconductive unit is used to directly sense the material to be detected, and the back side of the contact electrode of the photoconductive unit is connected to the signal input terminal to form the sensing part of the 3T direct detection circuit. By controlling the dual-gate thin-film transistor and the single-gate thin-film transistor to operate in the subthreshold range, the output voltage of the dual-gate thin-film transistor is logarithmically related to the incident light intensity of the photoconductive unit. This is used to broaden the dynamic response range of the 3T direct detection circuit and to make the single-gate thin-film transistor act as an in-pixel amplifier, thereby improving the sensitivity of the 3T direct detection circuit under weak light conditions. In other words, the dynamic response range of the 3T direct detection circuit is expanded by lowering the detection lower limit of the photodiode. The single-gate thin-film transistor II acts as a switching transistor to control the readout of the 3T direct probe circuit.

7. The high-performance 3T circuit according to any one of claims 5 or 6, characterized in that, The bias voltage connected to the drain of the first single-gate thin-film transistor is grounded with the source of the second double-gate thin-film transistor, so that the drain of the second single-gate thin-film transistor is used as the output terminal.

8. The high-performance 3T circuit according to claim 1, characterized in that, It also includes multiple passive pixel units; Multiple passive pixel units are connected in parallel to the signal input terminal of the 3T amplifier circuit to form a 3T passive pixel amplifier circuit; The passive pixel unit to be read in the 3T passive pixel amplifier circuit is selected by the row selection function to achieve pixel amplification. The 3T amplifier circuit is used as an external amplifier circuit so that only one switching thin film transistor is needed in each of the multiple passive pixel units. This is used to improve the pixel fill rate of the 3T passive pixel amplifier circuit, while also having the high sensitivity and wide dynamic range performance of the 3T amplifier circuit.

9. The high-performance 3T circuit according to claim 8, characterized in that, The passive pixel unit includes a photodiode and a switching thin-film transistor; The anode of the photodiode is connected to the drain of the switching thin-film transistor, and the source of the switching thin-film transistor is connected to the signal input terminal.

10. The high-performance 3T circuit according to any one of claims 8 or 9, characterized in that, Multiple 3T amplifier circuits are arranged in an array, and each of the multiple 3T amplifier circuits is connected to the 3T passive pixel amplifier circuit. Multiple columns of the 3T passive pixel amplifier circuits form a passive pixel matrix to improve the detection resolution.

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