Analog front-end circuit and touch sensing circuit

Abstract

The analog front-end circuit comprises a reference voltage source, a first capacitor, an amplifier and a second capacitor. The first capacitor is coupled to a reference voltage source through the switch. The amplifier includes a first input to receive a touch sensing signal from the touch sensor, a second input to receive a reference signal from the first capacitor, and an output to output an output signal. The second capacitor is arranged between the first input end and the second input end.

Description

Background Art

[0001] The present invention relates to an analog front end (AFE) circuit, and in particular to a touch control AFE circuit for reducing noise interference of a display.

[0002] When metal materials are used instead of transparent materials in touch panels, the touch panel needs to be placed as close to the display as possible to obtain a better display effect. However, noise interference from the display may cause errors in the touch signal. Summary of the invention

[0003] In one aspect, an analog front-end circuit is disclosed. The analog front-end circuit includes a reference voltage source, a first capacitor, an amplifier, and a second capacitor. The first capacitor is coupled to the reference voltage source through a switch. The amplifier includes a first input terminal for receiving a touch sensing signal from a touch sensor, a second input terminal for receiving a reference signal from the first capacitor, and an output terminal for outputting an output signal. The second capacitor is configured between the first input terminal and the second input terminal.

[0004] In some implementations, the analog front end circuit further includes a third capacitor disposed between the first input terminal and the touch sensor.

[0005] In some implementations, the analog front-end circuit further includes a fourth capacitor disposed between the first input terminal and the display.

[0006] In some embodiments, the analog front-end circuit further includes a fifth capacitor disposed between the first input terminal and the output terminal, a sixth capacitor disposed between the first input terminal and the third capacitor, and a first resistor disposed between the output terminal and the third capacitor.

[0007] In some embodiments, the sixth capacitor includes a first terminal coupled to the first input terminal and the fourth capacitor, and a second terminal coupled to the first resistor, the second capacitor, and the third capacitor.

[0008] In some embodiments, the capacitance value of the fifth capacitor is between 0.1 pF and 5 pF, and the capacitance value of the sixth capacitor is between 0.1 pF and 5 pF.

[0009] In some embodiments, a capacitance ratio of the fifth capacitor to the sixth capacitor is between 0.1 and 5.

[0010] In some embodiments, the capacitance of the first capacitor is between 1 pF and 200 pF, and the capacitance of the second capacitor is between 50 fF and 5 pF.

[0011] In some embodiments, the analog front-end circuit further includes a first resistor disposed between the output terminal and the third capacitor, a second resistor disposed between the first input terminal and the output terminal, and a third resistor disposed between the first input terminal and the third capacitor.

[0012] In some embodiments, the third resistor includes a first terminal coupled to the first input terminal and the second resistor, and a second terminal coupled to the first resistor, the second capacitor, and the third capacitor.

[0013] In some embodiments, the resistance of the second resistor is between 200 ohms and 4000 ohms, and the resistance of the third resistor is between 200 ohms and 4000 ohms.

[0014] In some embodiments, a resistance ratio of the second resistor to the third resistor is between 0.1 and 5.

[0015] In some implementations, the analog front-end circuit further includes an integrator circuit. The integrator circuit includes a first integration input terminal coupled to the amplifier output terminal, a second integration input terminal coupled to a reference voltage source, and an integration output terminal.

[0016] In some embodiments, the analog front end circuit further includes a fourth resistor disposed between the first integrator input terminal and the output terminal of the amplifier, and a seventh capacitor disposed between the first integrator input terminal and the integrator output terminal.

[0017] In another aspect, a touch sensing circuit is disclosed. The touch sensing circuit includes an analog front end circuit, an integration circuit and an analog-to-digital converter.

[0018] The analog front-end circuit includes a reference voltage source, a first capacitor, an amplifier, and a second capacitor. The first capacitor is coupled to the reference voltage source through a switch. The amplifier includes a first input terminal for receiving a touch sensing signal from a touch sensor, a second input terminal for receiving a reference signal from the first capacitor, and an output terminal for outputting an output signal. The second capacitor is configured between the first input terminal and the second input terminal. The integration circuit includes a first integration input terminal coupled to the amplifier output terminal, a second integration input terminal coupled to the reference voltage source, and an integration output terminal. The analog-to-digital converter is coupled to the integrator output terminal.

[0019] In some embodiments, the analog front-end circuit further includes a third capacitor disposed between the first input terminal and the touch sensor, and a fourth capacitor disposed between the first input terminal and the display.

[0020] In some embodiments, the analog front end circuit further includes a fifth capacitor disposed between the first input terminal and the output terminal, a sixth capacitor disposed between the first input terminal and the third capacitor, and a first resistor disposed between the output terminal and the third capacitor.

[0021] In some embodiments, the sixth capacitor includes a first terminal coupled to the first input terminal and the fourth capacitor, and a second terminal coupled to the first resistor, the second capacitor, and the third capacitor.

[0022] In some embodiments, the analog front end circuit further includes a first resistor disposed between the output terminal and the third capacitor, a second resistor disposed between the first input terminal and the output terminal, and a third resistor disposed between the first input terminal and the third capacitor.

[0023] In some implementations, the integrator circuit further includes a fourth resistor disposed between the first integrator input terminal and the output terminal of the amplifier, and a seventh capacitor disposed between the first integrator input terminal and the integrator output terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, further explain the present disclosure and enable those skilled in the relevant art to make and use the present disclosure.

[0025] Figure 1 Schematic diagram illustrating a cross-section of a display and touch panel according to some aspects of the present disclosure.

[0026] Figure 2 Illustrated is a schematic diagram showing noise interference from a display to an analog front end circuit according to some aspects of the present disclosure.

[0027] Figure 3 A schematic diagram of an exemplary analog front end circuit according to some aspects of the present disclosure is illustrated.

[0028] Figure 4 A schematic diagram of an exemplary analog front end circuit according to some aspects of the present disclosure is illustrated.

[0029] Figure 5 A schematic diagram of an exemplary analog front end circuit according to some aspects of the present disclosure is illustrated.

[0030] Figure 6 A schematic diagram of an exemplary analog front end circuit according to some aspects of the present disclosure is illustrated.

[0031] Figure 7 A schematic diagram of an exemplary analog front end circuit according to some aspects of the present disclosure is illustrated.

[0032] The present disclosure will be described with reference to the accompanying drawings. DETAILED DESCRIPTION

[0033] Although specific configurations and arrangements are discussed, it should be understood that this is for illustrative purposes only. Therefore, other configurations and arrangements may be used without departing from the scope of the present disclosure. In addition, the present disclosure may also be used for various other applications. The functions and structural features described in the present disclosure may be combined, adjusted and modified with each other, and in a manner not specifically depicted in the accompanying drawings, so that these combinations, adjustments and modifications are within the scope of the present disclosure.

[0034] In general, terms may be understood, at least in part, from usage in context. For example, the term "one or more" as used herein may be used to describe any feature, structure, or characteristic in a singular sense, or may be used to describe a combination of features, structures, or characteristics in a plural sense, depending, at least in part, on the context. Similarly, terms such as "one," "single," or "the" may be understood to convey singular usage or to convey plural usage, depending, at least in part, on the context. Further, the term "based on" may be understood to not necessarily be intended to convey a set of exclusive factors, but may allow for the presence of additional factors that are not explicitly described, again, depending, at least in part, on the context.

[0035] It should be readily understood that the meanings of “on,” “above,” and “covering” in this disclosure should be interpreted in the broadest manner, so that “on” means not only “directly on” something, but also means to include the meaning of “on” something with intermediate features or intermediate layers. Similarly, “above” or “covering” not only simply means “on something” or “covering something,” but also means that it “covers” or “on” something (i.e., directly on) without intermediate features or layers.

[0036] Additionally, spatially relative terms, such as "below," "below," "lower," "above," "upper," etc., may be used herein for ease of description to describe the relationship of one element or feature to another element or feature as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be described accordingly.

[0037] As used herein, the term "coupled to" or "connected to" refers to an electrical connection between two circuit nodes or a direct connection between two circuit nodes. The connection can be made through other devices or wires, such as wires, capacitors, resistors, transistors, conductors, amplifiers, or any capable device. The connection can also be made through direct wiring. The term "capacitance" refers to physical capacitance, parasitic capacitance, sensing capacitance, or any other suitable means.

[0038] Figure 1 1 is a schematic diagram illustrating a cross-section of a touch display 100 formed by a display 102 and a touch panel 104 according to some aspects of the present disclosure. Figure 1 As shown, the display 102 may include an anode layer 106, a light emitting element 107, and a cathode layer 108. In some embodiments, the display 102 may be an organic light emitting diode (OLED) display. In some embodiments, the light emitting element 107 may be formed by a plurality of intermediate layers, such as an electron transport layer, a blocking layer, an emission layer, a hole transport layer, and a hole injection layer. In some embodiments, the anode layer 106 and the cathode layer 108 may be formed at the bottom and top of the intermediate layer for driving the display 102.

[0039] In some embodiments, the touch panel 104 may include a metal grid layer 112 and a protective layer 114 for sensing a user's touch operation. In some embodiments, the metal grid layer 112 may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), indium gallium oxide (IGO) and / or aluminum zinc oxide (AZO). In some embodiments, the display 102 may be a foldable active matrix organic light emitting diode (AMOLED), and the metal grid layer 112 may be formed of indium gallium oxide (IGO). In some embodiments, the touch display 100 may also include a cover glass 116 and an optically clear adhesive (OCA) layer for bonding the cover glass 116 to the touch panel 104.

[0040] Figure 2 Schematic diagram of noise interference from the display 102 to the analog front end (AFE) circuit of the touch panel 104 according to some aspects of the present disclosure. In some embodiments, the display 102 and the touch panel 104 can be insulated by an insulator 110. In some embodiments, the distance between the metal mesh layer 112 of the touch panel 104 and the cathode layer 108 of the display 102 can be formed very close, for example, between 4-12 microns. Figure 2As shown, during operation of the display 102, a data line signal can be applied to the data line, such as the anode layer 106. A capacitor Ca is formed between the anode layer 106 and the cathode layer 108, and a capacitor Cb is formed between the cathode layer 108 and the touch panel 104, such as the metal mesh layer 112. In some embodiments, for example, the capacitor Cb can be as large as 500pF, the noise caused by the data line of the display 102 can be as large as 1 volt (V), and the charge injected into the touch panel 104 by the display noise can be about 500pC per data line. In some embodiments, the mutual capacitance variation in the touch panel 104 can be in the range of 50fF to 150fF, and the self-capacitance variation in the touch panel 104 can be in the range of 50fF to 200fF. When the measurement signal voltage of the touch panel 104 is as high as 6 volts, the charge injected into the AFE circuit by the metal mesh layer 112 can reach 900fC. Comparing the charge injected by the metal mesh layer 112 and the display noise, the AFE circuit needs to be able to amplify the touch panel signal for an analog-to-digital converter (ADC) without being clipped by the huge display noise.

[0041] Figure 3 2 illustrates a schematic diagram of an exemplary analog front end circuit 300 according to some aspects of the present disclosure. Figure 3 As shown, the analog front-end circuit 300 may include an operational amplifier 302. The touch sensing signal VTx and the display noise signal from the touch sensor of the touch panel 104 are provided to the first input terminal of the operational amplifier 302. Further, the second input terminal of the operational amplifier 302 provides a fixed reference voltage source Vref. Capacitor 304 (Cb) is formed between the cathode layer 108 and the touch panel 104, capacitor 306 (Cm) is the mutual capacitance to be measured, and capacitor 308 (Cf) is the charge amplifier feedback capacitor. In some embodiments, the voltage Vout at the output terminal of the operational amplifier 302 can be expressed as Vout = (-Cm / Cf×VTx).

[0042] However, in some implementations, since the capacitance of capacitor 304 is large compared to capacitor 306 , the displayed noise from capacitor 304 may result in a poor signal-to-noise ratio (SNR), while analog front end circuit 300 may easily reach the maximum or minimum operating range.

[0043] Figure 4 Schematic diagram of an exemplary analog front end circuit 400 according to some aspects of the present disclosure is shown. Figure 4As shown, the analog front-end circuit 400 includes an operational amplifier 402. The touch sensing signal VTx and the display noise signal from the touch sensor of the touch panel 104 are provided to the first input terminal of the operational amplifier 402. Further, the second input terminal of the operational amplifier 402 provides a reference voltage source Vref. The capacitor 404 (Cb) is formed between the cathode layer 108 and the touch panel 104, the capacitor 406 (Cm) is the mutual capacitance to be measured, and the capacitor 408 (Cf) is the charge amplifier feedback capacitor.

[0044] A reference capacitor 414 (Cref) is coupled to a reference voltage source Vref via a switch 412. A sampling capacitor 410 (Cx) is disposed between a first input terminal and a second input terminal of the operational amplifier 402. In some embodiments, the switch 412 may be initially closed, and the reference voltage source Vref may charge the reference capacitor 414 to a voltage Vref_float. Then, the switch 412 may be opened, and the reference capacitor 414 may remain floating with a voltage Vref_float. When the sampling capacitor 410 samples the voltage at the first input terminal of the operational amplifier 402, the sampling capacitor 410 may feed it to the reference capacitor 414 with a voltage Vref_float. The voltage at the reference capacitor 414 may change in the same direction as the voltage sampled at the first input terminal of the operational amplifier 402, which may minimize the interference of noise on the output voltage Vout at the output terminal of the operational amplifier 402.

[0045] Figure 5 Schematic diagram of an exemplary analog front end circuit 500 according to some aspects of the present disclosure is shown. Figure 5 As shown, the analog front-end circuit 500 includes an operational amplifier 502. The touch sensing signal VTx and the display noise signal from the touch sensor of the touch panel 104 are provided to the first input terminal of the operational amplifier 502. Further, the second input terminal of the operational amplifier 502 provides a reference voltage source Vref. Capacitor 504 (Cb) is formed between the cathode layer 108 and the touch panel 104, and capacitor 506 (Cm) is the mutual capacitance to be measured. Reference capacitor 514 (Cref) is coupled to the reference voltage source Vref through switch 512. Sampling capacitor 510 (Cx) is set between the first input terminal and the second input terminal of the operational amplifier 502.

[0046] like Figure 5 As shown, a capacitor 522 (C1) is arranged between the first input terminal of the operational amplifier 502 and the sampling capacitor 510, a capacitor 524 (C2) is arranged between the first input terminal and the output terminal of the operational amplifier 502, and a feedback resistor 526 (Rf) is arranged between the output terminal of the operational amplifier 502 and the sampling capacitor 510.

[0047] In some embodiments, capacitor 522 (C1) and capacitor 524 (C2) are used as an operational amplifier gain scaler to control the gain of operational amplifier 502 by the ratio of C1 / C2. In some embodiments, the capacitance of capacitor 522 can be between 0.1pF and 5pF. In some embodiments, the capacitance of capacitor 522 can be between 0.5pF and 2pF. In some embodiments, the capacitance of capacitor 524 can be between 0.1pF and 5pF. In some embodiments, the capacitance of capacitor 524 can be between 0.5pF and 2pF. In some embodiments, the capacitance ratio (C1 / C2) of capacitor 522 and capacitor 524 can be controlled between 0.1 and 5. In some embodiments, the capacitance ratio (C1 / C2) of capacitor 522 and capacitor 524 can be controlled between 0.5 and 2. In some embodiments, the capacitance of reference capacitor 514 can be between 1pF and 200pF. In some embodiments, the capacitance of reference capacitor 514 can be between 2 pF and 100 pF. In some embodiments, the capacitance of sampling capacitor 510 can be between 50 fF and 5 pF. In some embodiments, the capacitance of sampling capacitor 510 can be between 100 fF and 2 pF. Feedback resistor 526 is used to adjust the voltage of the touch sensor of touch panel 104 at node Rx.

[0048] In some implementations, when display noise is common to all channels, the output voltage Vout at the output of the operational amplifier 502 can be controlled to remain at or close to Vref, thereby minimizing interference of noise on the output voltage Vout at the output of the operational amplifier 502 .

[0049] Figure 6 1 illustrates a schematic diagram of an exemplary analog front end circuit 600 according to some aspects of the present disclosure. Figure 6 As shown, the analog front-end circuit 600 includes an operational amplifier 602. The touch sensing signal VTx and the display noise signal from the touch sensor of the touch panel 104 are provided to the first input terminal of the operational amplifier 602. Further, the second input terminal of the operational amplifier 602 provides a reference voltage source Vref. Capacitor 604 (Cb) is formed between the cathode layer 108 and the touch panel 104, and capacitor 606 (Cm) is the mutual capacitance to be measured. Reference capacitor 614 (Cref) is coupled to the reference voltage source Vref through switch 612. Sampling capacitor 610 (Cx) is set between the first input terminal and the second input terminal of the operational amplifier 602.

[0050] like Figure 6As shown, a resistor 622 (R1) is provided between the first input terminal of the operational amplifier 602 and the sampling capacitor 610, a resistor 624 (R2) is provided between the first input terminal and the output terminal of the operational amplifier 602, and a feedback resistor 626 (Rf) is provided between the output terminal of the operational amplifier 602 and the sampling capacitor 610.

[0051] In some embodiments, resistor 622 (R1) and resistor 624 (R2) are used as an operational amplifier gain scaler to control the gain of operational amplifier 602 by the ratio of R1 / R2. In some embodiments, the resistance of resistor 622 can be between 200 ohms and 4000 ohms. In some embodiments, the resistance of resistor 622 can be between 500 ohms and 2000 ohms. In some embodiments, the resistance of resistor 624 can be between 200 ohms and 4000 ohms. In some embodiments, the resistance of resistor 624 can be between 500 ohms and 2000 ohms. In some embodiments, the resistance ratio (R1 / R2) of resistor 622 and resistor 624 can be controlled between 0.1 and 5. In some embodiments, the resistance ratio (R1 / R2) of resistor 622 and resistor 624 can be controlled between 0.5 and 2.

[0052] In some embodiments, the capacitance of reference capacitor 614 may be between 1 pF and 200 pF. In some embodiments, the capacitance of reference capacitor 614 may be between 2 pF and 100 pF. In some embodiments, the capacitance of sampling capacitor 610 may be between 50 fF and 5 pF. In some embodiments, the capacitance of sampling capacitor 610 may be between 100 fF and 2 pF. Feedback resistor 626 is used to adjust the voltage of the touch sensor of touch panel 104 at node Rx.

[0053] In some implementations, when display noise is common to all channels, the output voltage Vout at the output of the operational amplifier 602 can be controlled to remain at or close to Vref, thereby minimizing the interference of noise on the output voltage Vout at the output of the operational amplifier 602 .

[0054] Figure 7 A schematic diagram of an exemplary analog front end circuit 700 according to some aspects of the present disclosure is illustrated. In some embodiments, since the analog front end circuit 400, 500, and / or 600 can act as a differentiator circuit for the input signal in the touch sensing circuit, an integrator may be required at the output of the analog front end circuit 400, 500, and / or 600 to recover the signal. The differentiator circuit can be similar to the analog front end circuit 400, 500, and / or 600, Figure 7 The differential circuit in the example is the analog front end circuit 600.

[0055] like Figure 7 As shown, the analog front-end circuit 700 includes an operational amplifier 702. The touch sensing signal VTx and the display noise signal from the touch sensor of the touch panel 104 are provided to the first input terminal of the operational amplifier 702. Further, the second input terminal of the operational amplifier 702 provides a reference voltage source Vref. Capacitor 704 (Cb) is formed between the cathode layer 108 and the touch panel 104, and capacitor 706 (Cm) is the mutual capacitance to be measured. Reference capacitor 714 (Cref) is coupled to the reference voltage source Vref through switch 712. Sampling capacitor 710 (Cx) is set between the first input terminal and the second input terminal of the operational amplifier 702.

[0056] like Figure 7 As shown, a resistor 722 (R1) is provided between the first input terminal of the operational amplifier 702 and the sampling capacitor 710. A resistor 724 (R2) is provided between the first input terminal and the output terminal of the operational amplifier 702, and a feedback resistor 726 (Rf) is provided between the output terminal of the operational amplifier 702 and the sampling capacitor 710.

[0057] In some embodiments, resistor 722 (R1) and resistor 724 (R2) are used as an operational amplifier gain scaler to control the gain of operational amplifier 702 by the ratio of R1 / R2. In some embodiments, the resistance of resistor 722 can be between 200 ohms and 4000 ohms. In some embodiments, the resistance of resistor 722 can be between 500 ohms and 2000 ohms. In some embodiments, the resistance of resistor 724 can be between 200 ohms and 4000 ohms. In some embodiments, the resistance of resistor 724 can be between 500 ohms and 2000 ohms. In some embodiments, the resistance ratio (R1 / R2) of resistor 722 and resistor 724 can be controlled between 0.1 and 5. In some embodiments, the resistance ratio (R1 / R2) of resistor 722 and resistor 724 can be controlled between 0.5 and 2.

[0058] In some embodiments, the capacitance of reference capacitor 714 may be between 1 pF and 200 pF. In some embodiments, the capacitance of reference capacitor 714 may be between 2 pF and 100 pF. In some embodiments, the capacitance of sampling capacitor 710 may be between 50 fF and 5 pF. In some embodiments, the capacitance of sampling capacitor 710 may be between 100 fF and 2 pF. Feedback resistor 726 is used to adjust the voltage of the touch sensor of touch panel 104 at node Rx.

[0059] like Figure 7As shown, the analog front-end circuit 700 may further include an integration circuit. In some embodiments, the analog front-end circuit 700 may further include an operational amplifier 750, a resistor 752 (R3) disposed between the output terminal of the operational amplifier 702 and the first input terminal of the operational amplifier 750, and a capacitor 754 disposed between the first input terminal and the output terminal of the operational amplifier 750. A reference voltage source Vref is provided to the second input terminal of the operational amplifier 750.

[0060] like Figure 7 As shown, the output of the operational amplifier 702 may have a differentiator output. When the display noise is common to all channels, the output voltage Vout at the output of the operational amplifier 702 may be controlled to remain at or close to Vref. In other words, the floating reference input voltage applied to the differentiator circuit may suppress the common signal across channels. The integration circuit may be used to integrate the output signal of the differentiation circuit. In this case, the touch sensing signal VTx through the capacitor 706 (Cm) may be suppressed by the differentiation circuit. However, if the capacitor 706 (Cm) changes locally due to a finger touch, such a difference may appear at the output of the integration circuit, such as the output of the operational amplifier 750. Therefore, the interference of noise on the output voltage at the output of the operational amplifier 750 may be minimized.

[0061] The foregoing description of specific implementations can be readily modified and / or adapted to various applications. Therefore, such adaptations and modifications are intended to fall within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0062] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. An analog front-end circuit, comprising: Reference voltage source; a first capacitor coupled to a reference voltage source via a switch; Amplifiers, including: A first input terminal receiving a touch sensing signal from a touch sensor; a second input terminal receiving a reference signal from the first capacitor; and an output terminal for outputting an output signal; and The second capacitor is disposed between the first input terminal and the second input terminal.

2. The analog front-end circuit according to claim 1, characterized in that: Also includes: A third capacitor is disposed between the first input terminal and the touch sensor.

3. The analog front-end circuit according to claim 2, characterized in that: Also includes: A fourth capacitor is arranged between the first input terminal and the display.

4. The analog front end circuit according to claim 3, further comprising: A fifth capacitor disposed between the first input terminal and the output terminal; A sixth capacitor disposed between the first input terminal and the third capacitor; as well as A first resistor is arranged between the output terminal and the third capacitor.

5. The analog front-end circuit according to claim 4, characterized in that: The sixth capacitor includes a first end coupled to the first input end and the fourth capacitor, and a second end coupled to the first resistor, the second capacitor, and the third capacitor.

6. The analog front-end circuit according to claim 5, characterized in that: The capacitance value of the fifth capacitor is between 0.1 pF and 5 pF, and the capacitance value of the sixth capacitor is between 0.1 pF and 5 pF.

7. The analog front-end circuit according to claim 5, characterized in that: The capacitance ratio of the fifth capacitor to the sixth capacitor is between 0.1 and 5.

8. The analog front-end circuit according to claim 1, wherein: The capacitance value of the first capacitor is between 1 pF and 200 pF, and the capacitance value of the second capacitor is between 50 fF and 5 pF.

9. The analog front end circuit according to claim 2, further comprising: A first resistor is arranged between the output terminal and the third capacitor; A second resistor disposed between the first input terminal and the output terminal; as well as A third resistor is disposed between the first input terminal and the third capacitor.

10. The analog front-end circuit according to claim 9, characterized in that: The third resistor includes a first end coupled to the first input end and the second resistor, and a second end coupled to the first resistor, the second capacitor, and the third capacitor.

11. The analog front-end circuit according to claim 10, characterized in that: The resistance value of the second resistor is between 200 and 4000 ohms, and the resistance value of the third resistor is between 200 and 4000 ohms.

12. The analog front-end circuit according to claim 10, characterized in that: The resistance ratio of the second resistor to the third resistor is between 0.1 and 5.

13. The analog front end circuit of claim 2, further comprising: An integrator circuit comprising: a first integrator input terminal coupled to the output terminal of the amplifier; a second integrator input terminal coupled to a reference voltage source; and Integrator output.

14. The analog front end circuit of claim 13, further comprising: The fourth resistor is arranged between the input terminal of the first integrator and the output terminal of the amplifier; as well as The seventh capacitor is arranged between the first integrator input terminal and the integrator output terminal.

15. A touch sensing circuit, comprising: Analog front-end circuit, including: Reference voltage source; a first capacitor coupled to a reference voltage source via a switch; Amplifiers, including: A first input terminal receiving a touch sensing signal from a touch sensor; a second input terminal receiving a reference signal from the first capacitor; and an output terminal for outputting an output signal; and a second capacitor disposed between the first input terminal and the second input terminal; and An integrator circuit comprising: a first integrator input terminal coupled to the output terminal of the amplifier; a second integrator input terminal coupled to a reference voltage source; and Integrator output.

16. The touch sensing circuit according to claim 15, characterized in that: The analog front end circuit also includes: a third capacitor disposed between the first input terminal and the touch sensor; and A fourth capacitor is arranged between the first input terminal and the display.

17. The touch sensing circuit according to claim 16, wherein: The analog front end circuit also includes: A fifth capacitor disposed between the first input terminal and the output terminal; a sixth capacitor disposed between the first input terminal and the third capacitor; and A first resistor is arranged between the output terminal and the third capacitor.

18. The touch sensing circuit according to claim 17, wherein: The sixth capacitor includes a first end coupled to the first input end and the fourth capacitor, and a second end coupled to the first resistor, the second capacitor, and the third capacitor.

19. The touch sensing circuit according to claim 16, wherein: The analog front end circuit also includes: A first resistor is arranged between the output terminal and the third capacitor; a second resistor disposed between the first input terminal and the output terminal; and A third resistor is disposed between the first input terminal and the third capacitor.

20. The touch sensing circuit according to claim 15, wherein: The integrator circuit also includes: a fourth resistor disposed between the first integrator input terminal and the output terminal of the amplifier; and A seventh capacitor is arranged between the first integrator input terminal and the integrator output terminal.

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