Signal amplification circuit, touch chip and electronic device

Abstract

Embodiments of the present application provide a signal amplification circuit, a touch chip and an electronic device. The signal amplification circuit is applied to a touch screen including a plurality of detection electrodes. The signal amplification circuit includes a plurality of detection operational amplifiers and a feedback circuit. A first input terminal of the detection operational amplifier is connected to a corresponding detection electrode, a second input terminal is connected to a common mode voltage, a first output terminal outputs a first amplified signal, and a second output terminal outputs a second amplified signal. The feedback circuit generates a feedback signal according to the first amplified signals and the second amplified signals of the plurality of detection operational amplifiers, and provides the feedback signal to the first input terminal of the detection operational amplifier. The feedback circuit reduces the influence of noise on the signal amplification circuit.

Description

Technical Field

[0001] This utility model relates to a circuit, and more particularly to a signal amplification circuit, a touch chip, and an electronic device. Background Technology

[0002] Touchscreens and displays are widely used in electronic devices. Touchscreens typically use capacitive sensors for touch detection. When a conductor, such as a finger or stylus, touches the touchscreen of an electronic device, the capacitance corresponding to the detection electrodes near the touch location changes. By detecting this change in capacitance, the touch location and the user's action can be determined. Touchscreen detection is affected by noise; therefore, reducing the impact of noise on the capacitive detection of touchscreens is a pressing issue. Utility Model Content

[0003] One of the purposes of this application is to provide a signal amplification circuit, a touch chip, and an electronic device to solve the above-mentioned problems.

[0004] According to a first aspect of the present invention, a signal amplification circuit is provided for use in a touchscreen including multiple detection electrodes. The signal amplification circuit amplifies the detection signals from the detection electrodes. The signal amplification circuit includes: multiple detection operational amplifiers and a feedback circuit.

[0005] The detection operational amplifier includes a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input terminal is connected to the corresponding detection electrode, the second input terminal is connected to a common-mode voltage, the first output terminal outputs a first amplified signal, and the second output terminal outputs a second amplified signal. The first amplified signal and the second amplified signal are out of phase.

[0006] The feedback circuit includes multiple first input terminals and multiple second input terminals. The multiple first input terminals of the feedback circuit are respectively connected to the first output terminals of the multiple detection operational amplifiers, and the multiple second input terminals of the feedback circuit are respectively connected to the second output terminals of the multiple detection operational amplifiers. The feedback circuit is used to generate a feedback signal based on the first amplified signal and the second amplified signal, and provide the feedback signal to the first input terminals of the multiple detection operational amplifiers.

[0007] In one possible implementation, the feedback circuit includes: a first averaging circuit, a second averaging circuit, and a feedback operational amplifier. The first averaging circuit is connected to the first output terminals of the plurality of detection operational amplifiers and is used to average the first amplified signals from the plurality of detection operational amplifiers to obtain a first average voltage. The second averaging circuit is connected to the second output terminals of the plurality of detection operational amplifiers and is used to average the second amplified signals from the plurality of detection operational amplifiers to obtain a second average voltage. The feedback operational amplifier receives the first average voltage and the second average voltage and outputs a feedback voltage. The feedback voltage is proportional to the voltage difference between the first average voltage and the second average voltage.

[0008] In one possible implementation, the feedback circuit further includes: a plurality of feedback resistors connected between the output terminal of the feedback operational amplifier and the first input terminal of the detection operational amplifier, for outputting a feedback current based on the feedback voltage, wherein the feedback current is the feedback signal.

[0009] In one possible implementation, the feedback operational amplifier is a differential operational amplifier used to perform the subtraction of the second average voltage and the first average voltage.

[0010] In one possible implementation, the signal amplification circuit further includes a first feedback path and a second feedback path, wherein the first feedback path is disposed between the first input terminal and the second output terminal of the detection operational amplifier, and the second feedback path is disposed between the second input terminal and the first output terminal of the detection operational amplifier.

[0011] In one possible implementation, the first input terminal of the detection operational amplifier is a non-inverting input terminal, the second input terminal is an inverting input terminal, the first output terminal is a non-inverting output terminal, and the second output terminal is an inverting output terminal; or, the first input terminal of the detection operational amplifier is an inverting input terminal, the second input terminal is a non-inverting input terminal, the first output terminal is an inverting output terminal, and the second output terminal is a non-inverting output terminal.

[0012] According to a second aspect of the present invention, a signal amplification circuit is provided for use in a touchscreen including multiple detection electrodes. The signal amplification circuit includes:

[0013] Multiple detection operational amplifiers are provided, each operational amplifier including a first input terminal, a second input terminal, and an output terminal. The first input terminal is connected to the corresponding detection electrode, the second input terminal is connected to a common-mode voltage, and the output terminal outputs an amplified signal.

[0014] A third averaging circuit is used to obtain the average voltage of the multiple amplified signals of the multiple detection operational amplifiers;

[0015] A feedback operational amplifier for providing a feedback voltage proportional to the average voltage of the plurality of amplified signals; and

[0016] Multiple feedback resistors are connected between the output of the feedback operational amplifier and the first input of the detection operational amplifier.

[0017] In one possible implementation, the signal amplification circuit further includes a third feedback path, which is disposed between the output terminal and the first input terminal of the detection operational amplifier.

[0018] According to a third aspect of this utility model, a touch chip is provided. The touch chip includes the signal amplification circuits of the first and second aspects.

[0019] According to a fourth aspect of the present invention, an electronic device is provided. The electronic device includes: a touchscreen; and a touch chip according to a third aspect. The touchscreen includes a plurality of detection electrodes. The signal amplification circuit of the touch chip is used to amplify the detection signals from the detection electrodes.

[0020] In the signal amplification circuit of this application embodiment, the feedback circuit generates a feedback signal based on the first amplified signal and the second amplified signal of multiple detection operational amplifiers. The feedback signal is provided to the first input terminal of the detection operational amplifier, which reduces the magnitude of common noise in the output signal of the detection operational amplifier and avoids output saturation of the detection operational amplifier. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic block diagram of an electronic device according to an embodiment of this application.

[0023] Figure 2 This is a schematic diagram of a touchscreen according to an embodiment of this application.

[0024] Figure 3 This is a schematic block diagram of a touch chip according to an embodiment of this application.

[0025] Figure 4 This is a schematic diagram of display interference noise from the display screen to the touch screen.

[0026] Figure 5This is a schematic diagram of a signal amplification circuit according to an embodiment of this application.

[0027] Figure 6 This is a circuit diagram of a signal amplification circuit according to an embodiment of this application.

[0028] Figure 7 for Figure 6 A schematic diagram of the equivalent feedback loop of the signal amplification circuit.

[0029] Figure 8A and 8B The figures show the time-domain output signals of the channel with finger touch and the channel without finger touch in a signal amplifier circuit without feedback.

[0030] Figure 9A and 9B The images show the frequency domain diagrams of the output signal from the channel with finger touch and the output signal from the channel without finger touch in a signal amplifier circuit without feedback.

[0031] Figure 10A and 10B These are time-domain diagrams of the output signal of the channel with finger touch and the output signal of the channel without finger touch, respectively, in the signal amplification circuit of this application embodiment.

[0032] Figure 11A and 11B These are frequency domain diagrams of the output signal of the channel with finger touch and the output signal of the channel without finger touch, respectively, in the signal amplification circuit of this application embodiment.

[0033] Figure 12 This is a circuit diagram of another signal amplification circuit according to an embodiment of this application.

[0034] Figure 13 This is a circuit diagram of another signal amplification circuit according to an embodiment of this application.

[0035] Figure 14 This is a circuit diagram of another signal amplification circuit according to an embodiment of this application.

[0036] Figure 15 This is a circuit diagram of a signal amplifier circuit without feedback. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments in this application should fall within the scope of protection of this application.

[0038] Figure 1 This is a schematic block diagram of an electronic device according to an embodiment of this application. Figure 1 The electronic device includes: a touch screen 20, a display screen 30, a touch chip 10, and a display driver chip 40.

[0039] The display screen 30 includes, but is not limited to, liquid crystal displays (LCDs), organic light-emitting displays (OLEDs), plasma display panels (PDPs), micro LEDs, and mini LEDs. The touchscreen 20 is, for example, a capacitance-based touchscreen. The touchscreen 20 is located above the display screen 30. Users can use their fingers, styluses, or other conductors to touch the touchscreen 20 to perform corresponding touch operations. The display driver chip 40 outputs display drive signals to the display screen 30 to drive the display screen 30 to display images. The touch chip 10 outputs touch drive signals to the touchscreen 20 to achieve capacitance detection, thereby enabling user touch operations on the touchscreen 20.

[0040] In some embodiments, the touch chip 10 and the display driver chip 40 are two separate chips, each with its own independent package. In some embodiments, the touch chip 10 and the display driver chip 40 are integrated into a single chip, such as Touch and Display Driver Integration (TDDI).

[0041] As an example and not a limitation, the electronic device can be a terminal device, mobile phone, tablet, laptop, desktop computer, gaming device, in-vehicle electronic device, or wearable smart device, or other portable or mobile computing device, as well as electronic databases, automobiles, and automated teller machines (ATMs). Wearable smart devices include those that are fully functional, large in size, and capable of performing complete or partial functions without relying on a smartphone, such as smartwatches or smart glasses, as well as those that focus on a specific type of application function and require the use of other devices such as smartphones, such as various smart bracelets and smart jewelry for vital sign monitoring.

[0042] Figure 2 This is a schematic diagram of a touchscreen according to an embodiment of this application. Figure 2 As shown, the touchscreen 20 includes first electrodes TX1-TX extending along a first direction. m and the second electrode RX1-RX extending along the second direction n The first and second directions intersect. The touchscreen 20 can employ two detection methods: self-capacitance and mutual capacitance.

[0043] During self-capacitance detection, the touch chip 10 directs the signal to the first electrode TX. i (1≤i≤m) provides the drive signal to detect the first electrode TX. i The change in the self-capacitance Cs (i.e., the detection capacitance) to ground, and the first electrode TX i It serves as both a driving electrode and a detection electrode. Furthermore, the touch chip 10 directs the signal to the second electrode RX. j (1≤j≤n) provides the drive signal to detect the second electrode RX. j The change in the self-capacitance Cs to ground (i.e., the detection capacitance), and the second electrode RX. j It serves as both the driving electrode and the detection electrode. Based on the first electrode TX... i Second electrode RX j The change in the self-capacitance Cs to ground is used to identify the user's touch operation. Figure 2 With the first electrode TX m Self-capacitance Cs, second electrode RX n The self-capacitance Cs is used as an example.

[0044] During mutual capacitance detection, the first electrode TX i Second electrode RX j The first electrode TX serves as both the driving electrode and the detection electrode. i Second electrode RX j The coupling capacitance Cc between them serves as the detection capacitance. The touch chip 10 directs the first electrode TX1-TX... m Provide drive signals from the second electrode RX1-RX n The system receives detection signals to detect changes in the coupling capacitance Cc. For example, multiple first electrodes TX are grouped together, and multiple groups of first electrodes TX are driven sequentially until all first electrodes TX1-TX are used. m The driving process is complete, where the number of first electrodes in each group can be the same or different. The user's touch operation is identified based on changes in the coupling capacitance Cc, which is the detection capacitance. Figure 2 With the first electrode TX m-1 The coupling capacitance Cc between the second electrode RX2 is used as an example.

[0045] When performing self-capacitance detection, the self-capacitance Cs is the detection capacitor, and the first electrode TX and the second electrode RX are the detection electrodes. When performing mutual capacitance detection, the coupling capacitor Cc is the detection capacitor, the first electrode TX is the driving electrode, and the second electrode RX is the detection electrode. The following description uses mutual capacitance detection as an example. The signal amplification circuit and touch chip of this application are also applicable to self-capacitance detection.

[0046] Figure 3 This is a schematic block diagram of a touch chip according to an embodiment of this application. The touch chip 10 includes a driving circuit 300 and a signal amplification circuit 100 (also referred to as a detection circuit). The driving circuit 300 provides a driving signal to the first electrode TX. The signal amplification circuit receives the detection signal from the detection electrode, amplifies the detection signal, converts the amplified signal into a digital signal, and the touch chip 10 further processes the amplified signal to achieve the final touch detection function. The signal amplification circuit is, for example, an amplification circuit based on a transimpedance amplifier. The detection signal includes noise, such as display interference noise from the display screen 30 to the touch screen 20.

[0047] Figure 4 This is a schematic diagram of display interference noise on the touchscreen. The display screen 30 includes signal lines such as scan lines and data lines. The touchscreen 20 is located above the display screen 30. Due to coupling, the signals on the signal lines of the display screen 30 can interfere with the signals of the touchscreen 20. For example, when a scan signal is applied to the scan line of the display screen 30, the scan signal may couple onto the touchscreen 20. The smaller the distance between the touchscreen 20 and the display screen 20, the stronger the coupling. For example, display interference noise systematically interferes with the capacitance detection of the touchscreen 20 through the display screen 30, reducing the signal-to-noise ratio of capacitance detection and affecting the touch detection results. If the display interference noise is too large, it can also cause the operational amplifier output in the signal amplification circuit 100 to saturate, resulting in the inability to detect changes in the detection capacitance Cs and / or Cc. Figure 4 As shown, there is an equivalent capacitance Cd between the signal line of the display screen 30 and the system ground of the display screen 30, an equivalent capacitance C2 between the first electrode TX and the system ground of the display screen 30, and an equivalent capacitance C3 between the second electrode RX and the system ground of the display screen 30. Display interference noise enters the touch chip 10 through the equivalent capacitances Cd, C2, and C3, causing the detection signal to carry display interference noise. Therefore, as Figure 4 As shown, the signal VIN received by the first electrode TX includes both display interference noise and the drive signal provided by the drive circuit 300. Figure 4 As shown, the equivalent impedance from the first electrode TX to the signal amplification circuit 100 is denoted as ZIN.

[0048] Figure 5 This is a circuit diagram of the signal amplification circuit 100 according to an embodiment of this application. Figure 5 As shown, the signal amplification circuit 100 includes: multiple detection operational amplifiers 1101-110n, and a feedback circuit 14. Figure 5 In the diagram, C11-C1n represent the first electrode TX and the second electrode RX1-RX, respectively. n The coupling capacitor, or rather the driving electrode TX and the detection electrode RX1-RX n The coupling capacitances between them, VIP1-VIPn are the voltages at the first input terminal N1 of multiple detection operational amplifiers 1101-110n. Detection electrodes RX1-RX n The corresponding operational amplifiers 1101-110n are also known as the detection channels.

[0049] The detection operational amplifier 110j includes: a first input terminal N1, a second input terminal N2, a first output terminal O1, and a second output terminal O2. The detection operational amplifier 110j is one of multiple detection operational amplifiers 1101-110n, where 1 ≤ j ≤ n. One of the first input terminal N1 and the second input terminal N2 is a non-inverting input, and the other is an inverting input. One of the first output terminal O1 and the second output terminal O2 is a non-inverting output, and the other is an inverting output. The phase of the non-inverting input terminal is the same as the phase of the non-inverting output terminal, and the phase of the non-inverting output terminal is opposite to the phase of the inverting output terminal.

[0050] The first input terminal N1 is connected to the corresponding detection electrode RX and receives the detection signal provided by the detection electrode RX. The second input terminal N2 is connected to the terminal providing the common-mode voltage VCM, and the equivalent impedance from this terminal to the second input terminal N2 is Z3. The voltage at the second input terminal N2 is VN. The detection operational amplifier 110j amplifies the voltage difference between the voltage at the first input terminal N1 and the voltage at the second input terminal N2. The first output terminal O1 outputs a first amplified signal VOPj, and the second output terminal O2 outputs a second amplified signal VONj. The first amplified signal VOPj is one of multiple first amplified signals VOP1-VOPn, and the second amplified signal VONj is one of multiple second amplified signals VON1-VONn, where 1 ≤ j ≤ n. Both the first amplified signal VOPj and the second amplified signal VONj are amplified signals of the voltage difference between the voltage at the first input terminal N1 and the voltage at the second input terminal N2. The phase of the first amplified signal VOPj is opposite to the phase of the second amplified signal VONj. The output signal of the signal amplification circuit 100 includes the first amplified signal and the second amplified signal.

[0051] The signal amplification circuit 100 further includes multiple first feedback paths 111 and multiple second feedback paths 112. The first feedback path 111 is disposed between the first input terminal N1 and the second output terminal O2 of the detection operational amplifier 110j. For example, the first input terminal N1 is a non-inverting input terminal and the second output terminal O2 is an inverting output terminal; or, the first input terminal N1 is an inverting input terminal and the second output terminal O2 is a non-inverting output terminal. The first feedback path 111 includes a resistor and / or a capacitor. For example, the first feedback path 111 includes a resistor and a capacitor connected in parallel between the first input terminal N1 and the second output terminal O2. The equivalent impedance of the first feedback path 111 is Z1. The second feedback path 112 is disposed between the second input terminal N2 and the first output terminal O1 of the detection operational amplifier 110j. For example, the second input terminal N2 is a non-inverting input terminal and the first output terminal O1 is an inverting output terminal; or, the second input terminal N2 is an inverting input terminal and the first output terminal O1 is a non-inverting output terminal. The second feedback path 112 includes a resistor and / or a capacitor. For example, the second feedback path 112 includes a resistor disposed between the second input terminal N2 and the first output terminal O1, or includes a resistor and a capacitor connected in parallel between the second input terminal N2 and the first output terminal O1. The equivalent impedance of the second feedback path 112 is Z2.

[0052] The detection operational amplifier 110j, the first feedback path 111, the second feedback path 112, and the coupling capacitor C1j constitute a first amplification stage. This first amplification stage amplifies the received detection signal; in other words, it amplifies the signal VIN on the driving electrode TX, where 1 ≤ j ≤ n. The amplification factor of the first amplification stage is related to the coupling capacitor C1j. When a finger touches the touchscreen 20, the value of the coupling capacitor C1j changes, and the amplification factor of the first amplification stage changes. For example, finger contact with the touchscreen 20 causes the coupling capacitor C1j to decrease, thus decreasing the amplification factor of the first amplification stage. Therefore, the average deviation of the output signal (first amplified signal and second amplified signal) of the detection operational amplifier 110j relative to the output signals of the multiple detection operational amplifiers 1101-110n can characterize whether the coupling capacitor C1j corresponding to the detection operational amplifier 110j is affected by finger touch, thereby determining the touch position.

[0053] The first and second amplified signals output by the operational amplifier both include amplified signals of the detection signal; that is, the amplified signals include amplified signals of the drive signal and noise. Therefore, the first amplified signal VOPj can be expressed as the sum of an average and a variation: VOPj = VOP_AVERAGE + VOPj_variation. Here, the average VOP_AVERAGE is the average voltage of the multiple first amplified signals VOP1-VOPn, VOP_AVERAGE = (VOP1 + VOP2 + ... + VOPn) / n. The variation VOPj_variation is the deviation of the first amplified signal VOPj from the average VOP_AVERAGE. Therefore, the variation VOP1_variation - VOPn_variation of the multiple first amplified signals VOP1-VOPn satisfies VOP1_variation + VOP2_variation + ... + VOPn_variation = 0. The average value VOP_AVERAGE includes the amplified signal of noise, while the variation value VOPj_variation characterizes whether the coupling capacitance corresponding to the detection operational amplifier 110j has changed, thereby confirming the touch position. Similarly, the second amplified signal VONj can also be expressed as the sum of the average value VON_AVERAGE and the variation value VONj_variation.

[0054] Feedback circuit 14 includes multiple first input terminals and multiple second input terminals. The first input terminals are connected to the first output terminal O1 of the corresponding detection operational amplifier, and the second input terminals are connected to the second output terminal O2 of the corresponding detection operational amplifier. Feedback circuit 14 generates a feedback signal If based on the first amplified signal output from the first output terminal O1 and the second amplified signal output from the second output terminal O2, and provides the feedback signal If to the first input terminal N1 of the multiple detection operational amplifiers 1101-110n. Specifically, feedback circuit 14 obtains a first average voltage based on the first amplified signal output from the first output terminal O1, obtains a second average voltage based on the second amplified signal output from the second output terminal O2, and then generates the feedback signal If based on the first and second average voltages. The first average voltage is the average voltage VOP_AVERAGE of the first amplified signals VOP1-VOPn of the multiple detection operational amplifiers 1101-110n, and the second average voltage is the average voltage VON_AVERAGE of the second amplified signals VON1-VONn of the multiple detection operational amplifiers 1101-110n. For each detection operational amplifier, the first amplified signal and the second amplified signal are inverted signals with the same amplitude. Therefore, the first average voltage VOP_AVERAGE and the second average voltage VON_AVERAGE are also inverted signals with the same amplitude.

[0055] This application, by setting up a signal amplification circuit, uses a feedback circuit to process the first and second amplified signals output by the detection operational amplifier, and feeds the processed feedback signal back to the input of the detection operational amplifier. This makes the gain of the detection operational amplifier on the change of the input signal greater than the gain on the average amount of the input signal, thereby reducing the noise signal in the output signal of the detection operational amplifier and improving the accuracy of the touch chip in detecting the touch position.

[0056] Figure 6 This is a circuit diagram of the signal amplification circuit according to an embodiment of this application. Figure 6 As shown, the signal amplification circuit 100 includes: multiple detection operational amplifiers 1101-110n and a feedback circuit. Figure 6 In the diagram, C11-C1n represent the driving electrode TX and the detection electrodes RX1-RX, respectively. n The coupling capacitors between them, VIP1-VIPn are the voltages at the first input terminal N1 of multiple detection operational amplifiers 1101-110n. Figure 6 The signal amplification circuit shown contains multiple detection operational amplifiers 1101-110n and Figure 5 The multiple detection operational amplifiers 1101-110n in the signal amplification circuit shown are the same, and will not be described again here.

[0057] like Figure 6 As shown, the feedback circuit 14 includes: a first averaging circuit 120, a second averaging circuit 130, and a feedback operational amplifier 140.

[0058] The first averaging circuit 120 is connected to the first output terminal O1 of the plurality of detection operational amplifiers 1101-110n, and is used to obtain a first average voltage. The first average voltage is the average voltage VOP_AVERAGE of the first amplified signals VOP1-VOPn of the plurality of detection operational amplifiers 1101-110n. The first averaging circuit 120 is, for example, composed of a plurality of resistors, one end of which is connected to the first output terminal O1 of the corresponding detection operational amplifier, and the other end of which is connected to the output terminal.

[0059] The second averaging circuit 130 is connected to the second output terminal O2 of the plurality of detection operational amplifiers 1101-110n, and is used to obtain a second average voltage. The second average voltage is the average voltage VON_AVERAGE of the second amplified signals VON1-VONn of the plurality of detection operational amplifiers 1101-110n. The second averaging circuit 130 is, for example, composed of a plurality of resistors, one end of which is connected to the second output terminal O2 of the corresponding detection operational amplifier, and the other end of which is connected to the output terminal.

[0060] The feedback operational amplifier 140 is, for example, a differential operational amplifier. The feedback operational amplifier 140 includes a first input terminal, a second input terminal, and an output terminal. The first input terminal is one of a non-inverting input terminal and an inverting input terminal, and the second input terminal is the other of a non-inverting input terminal and an inverting input terminal. The first input terminal and the second input terminal receive a first average voltage VOP_AVERAGE and a second average voltage VON_AVERAGE, respectively. The output terminal of the feedback operational amplifier 140 provides a feedback voltage Vf proportional to the difference between the second average voltage VON_AVERAGE and the first average voltage VOP_AVERAGE. The phase of the feedback voltage Vf is opposite to the phase of the voltage VIP1 at the first input terminal N1 of the detection operational amplifier. For example, the feedback voltage Vf is proportional to the voltage difference between the second average voltage and the first average voltage, and the feedback voltage Vf = VON_AVERAGE - VOP_AVERAGE = 2 * VON_AVERAGE. The feedback operational amplifier 140 can, for example, implement the subtraction of the first average voltage VOP_AVERAGE and the second average voltage VON_AVERAGE. In an exemplary implementation, the first input terminal of the feedback operational amplifier 140 is connected to the output terminal of the second averaging circuit 130 to receive the second average voltage VON_AVERAGE, the second input terminal of the feedback operational amplifier 140 is connected to the output terminal of the first averaging circuit 120 to receive the first average voltage VOP_AVERAGE, and the output terminal of the feedback operational amplifier 140 is connected to the second input terminal of the feedback operational amplifier 140.

[0061] The feedback signal is generated based on the feedback voltage Vf. In some embodiments, the feedback circuit 14 further includes multiple feedback resistors 145. The feedback resistors 145 are connected between the output of the feedback operational amplifier 140 and the first input N1 of the corresponding detection operational amplifier 110j. The feedback resistors 145 convert the feedback voltage Vf output by the feedback operational amplifier 140 into a feedback current If, and feed it back to the first input N1 of the corresponding detection operational amplifier 110j. The feedback current If is the feedback signal. The phase of the voltage VIP1 at the first input N1 of the detection operational amplifier is the same as the phase of the voltage on the detection electrode RX, and the phase of the voltage VIP1 at the first input N1 of the detection operational amplifier is opposite to the phase of the feedback voltage Vf. Therefore, the direction of the current between the detection electrode RX and the first input N1 is opposite to the direction of the current on the feedback resistor 145.

[0062] The touch chip 10 also includes an analog-to-digital converter (ADC). The ADC is connected to the output of the detection operational amplifier and is used to convert the amplified signal output by the detection operational amplifier into a digital signal. In some embodiments, the signal amplification circuit 100 further includes a filter circuit (not shown), which is disposed between the detection operational amplifier and the ADC to reduce noise in the amplified signal.

[0063] This application, through the configuration of the signal amplification circuit, utilizes a first averaging circuit 120 to obtain a first average voltage of multiple first amplified signals, and a second averaging circuit 130 to obtain a second average voltage of multiple second amplified signals. A feedback operational amplifier 140 obtains a feedback voltage based on the first and second average voltages, and a feedback resistor 145 converts the feedback voltage into a feedback current. The feedback current is fed back to the first input terminal N1 of the detection operational amplifier, making the gain of the detection operational amplifier for the change in the input signal greater than the gain for the average amount of the input signal. Therefore, the noise signal in the output signal of the detection operational amplifier is reduced, and the accuracy of the touch chip in detecting the touch position is improved.

[0064] Figure 7 for Figure 6 A schematic diagram of the equivalent feedback loop of a signal amplifier circuit. (See diagram below.) Figure 6 and Figure 7 As shown, the transfer coefficient from the second output terminal O2 of the detection operational amplifier to the first input terminal N1 of the detection operational amplifier is D, the transfer coefficient from the first output terminal O1 of the detection operational amplifier to the second input terminal N2 of the detection operational amplifier is B, the transfer coefficient from the driving electrode TX to the first input terminal N1 of the detection operational amplifier is C, A(F) is the open-loop gain of the detection operational amplifier, and VE is the voltage difference between the first input terminal N1 and the second input terminal N2 of the detection operational amplifier. Combined with... Figure 4 The equivalent impedance ZIN from the driving electrode TX to the first input terminal N1 of the detection operational amplifier can be regarded as the equivalent impedance of the coupling capacitor Cc and the equivalent capacitors C2 and C3. Figure 6 The feedback loop rejection ratio of the signal amplifier circuit is derived as follows.

[0065] The following analysis uses the operational amplifier 1101 as an example. The example assumes that the first input terminal N1 is the non-inverting input, the second input terminal N2 is the inverting input, the first output terminal O1 is the non-inverting output, and the second output terminal O2 is the inverting output. According to Kirchhoff's laws, the current flowing into the first input terminal N1 is equal to the current flowing out of the first input terminal N1. The current flowing into the operational amplifier 1101 from the first input terminal N1 is essentially zero. The current from the drive electrode TX to the first input terminal N1 of the operational amplifier 1101 is... Where VIP1 is the voltage at the first input terminal N1 of the operational amplifier 1101, and VIN is the voltage on the drive electrode TX. The current from the first input terminal N1 to the second output terminal O2 is... Where VON1 is the voltage at the second output terminal O2. The current from the first input terminal N1 to the output terminal of the feedback operational amplifier 140 is the feedback current If, and the magnitude of the feedback current If is... 2*VON_AVERAGE is the feedback voltage Vf output by the feedback operational amplifier 140. The resistance of the feedback resistor 145 is Rf. Therefore, we can obtain the following formula 1.

[0066]

[0067] As analyzed above, finger contact with the touchscreen 20 causes a change in the coupling capacitance between the driving electrode TX and the detection electrode RX (the number of changing coupling capacitances is less than the number of unchanged coupling capacitances), which in turn leads to a change in the equivalent impedance ZIN. That is, the equivalent impedance ZIN corresponding to the detection channel in the touch area is different from the equivalent impedance ZIN corresponding to the detection channel in the non-touch area. The signal VIN of the driving electrode TX can be represented as an average value VIN_average and a variation value VIN_variation. The variation value VIN_variation corresponds to the change in equivalent impedance ZIN caused by the touch. Therefore, the noise component in the signal VIN of the driving electrode TX is located at the average value VIN_average, while the driving signal provided by the driving circuit 300 is located at the variation value VIN_variation.

[0068] The voltage VIP1 at the first input terminal N1 can be expressed as the sum of the average value VIP_average and the variation VIP1_variation. The average value VIP_average is the average voltage across the first input terminal N1 of multiple sensing operational amplifiers 1101-110n: VIP_average = (VIP1 + VIP2 + ... + VIPn) / n. The variation VIP1_variation is the deviation of the voltage VIP1 at the first input terminal N1 of the sensing operational amplifier 1101 from the average voltage VIP_average, i.e.: VIP1_variation = VIP1 - VIP_average. The average value VIP_average includes the portion of common noise that reaches the first input terminal N1 after being transmitted through the equivalent impedance Zin.

[0069] The first amplified signal VOP1 output from the first output terminal O1 is the amplified signal of VE, and therefore includes both the average value VOP_AVERAGE and the variation value VOP1_variation. The average value VOP_AVERAGE is equal to the average voltage of the first amplified signals from the multiple detection operational amplifiers 1101-110n: VOP_AVERAGE = (VOP1 + VOP2 + ... + VOPn) / n. The variation value VOP1_variation is the deviation of the first amplified signal VOP1 from the average voltage VOP_AVERAGE.

[0070] The second amplified signal VON1 output from the second input terminal O2 is also an amplified signal of VE, therefore it includes both the average value VON_AVERAGE and the variation VON1_variation. The average value VON_AVERAGE is equal to the average voltage of the second amplified signals from the multiple detection operational amplifiers 1101-110n: VON_AVERAGE = (VON1 + VON2 + ... + VONn) / n. The variation VON1_variation is the deviation of the second amplified signal VON1 from the average voltage VON_AVERAGE.

[0071] Substituting the average and change of the signal VIN on the driving electrode TX and the second amplified signal VON1 into Formula 1 yields Formula 2.

[0072]

[0073] Formula 2 can be split into Formula 3 and Formula 4.

[0074]

[0075] The current flowing into the detection operational amplifier from the second input terminal N2 is basically 0. Applying Kirchhoff's laws to the second input terminal N2, we can obtain Formula 5.

[0076]

[0077] For the detection operational amplifier 1101, the voltage VN at the second input terminal N2 includes an average value VN_average and a variation value VN_variation. The average value VN_average is equal to the average voltage of the voltages at the second input terminals N2 of multiple detection operational amplifiers 1101-110n. Substituting the average value and the variation value of the voltage VN at the second input terminal N2 into Equation 5 yields Equation 6.

[0078]

[0079] Formula 6 can be split into Formula 7 and Formula 8.

[0080]

[0081] Reference Figure 6 Circuit diagram and Figure 7 The equivalent loop, the voltage VIP1 at the first input terminal N1 can be expressed as VIP1=VIN*C+VON1*D, and the voltage VN at the second input terminal N2 can be expressed as VN=VOP1*B=-VON1*B.

[0082] According to formulas 3 and 4, the path from the driving electrode TX of the detection capacitor to the first input terminal N1 of the detection operational amplifier has the same transfer coefficient for both the average and the change, and the transfer coefficient C is:

[0083]

[0084] According to formulas 3 and 4, the transfer coefficients D(average) and D(variation) of the path from the second output terminal O2 to the first input terminal N1 are respectively:

[0085]

[0086] According to formulas 7 and 8, the path from the first output terminal O1 to the second input terminal N2 has the same transfer coefficient for both the average and the change, and the transfer coefficient B is:

[0087]

[0088] The voltage difference VE = VIP1 - VN = VIN*C + (D + B)*VON1 is detected at the first input terminal N1 and the second input terminal N2 of operational amplifier 1101. The second amplified signal VON1 output by operational amplifier is detected as A(F)*VE. Therefore, Formula 13 can be obtained.

[0089] VON1*(1-A(F)*(D+B))=VIN*A(F)*C Formula 13

[0090] Right now

[0091] The gain of the signal amplifier circuit 100 on the average amount of the signal VIN on the drive electrode TX can be expressed as Equation 15.

[0092]

[0093]

[0094] The gain of the signal amplification circuit 100 for the change in signal VIN on the drive electrode TX can be expressed as Equation 16.

[0095]

[0096] To simplify the analysis, assume that the equivalent impedance Z2 of the second feedback path 112 and the equivalent impedance Z3 of the common-mode voltage VCM to the second input terminal N2 satisfy the following: Z2 / Z3 is much greater than 1, and the transfer coefficient B from the first output terminal O1 to the second input terminal N2 is approximately equal to 0. Further, equations 17 and 18 can be obtained from equations 15 and 16.

[0097]

[0098] The open-loop gain AF of an operational amplifier is typically large, therefore equations 17 and 18 can be further simplified to the formula...

[0099] Equations 19 and 20.

[0100]

[0101] According to formulas 19 and 20, the gain of the signal amplifier circuit 100 on the average value of the signal VIN at the driving electrode TX is less than the gain of the signal amplifier circuit 100 on the change value of the signal VIN at the driving electrode TX. That is, the gain of the signal amplifier circuit for the useful signal is greater than the gain for the common noise.

[0102] Figure 15 A signal amplifier circuit without feedback circuitry is shown. Figure 15 The signal amplification circuit shown has a gain of -Z1 / ZIN for both the average and variable values ​​of the signal VIN at the driving electrode TX. As can be seen from equations 19 and 20, the gain attenuation of the signal amplification circuit 100 in this application for the average value of the signal VIN at the driving electrode TX is... Figure 15 The gain of the circuit shown is 1 / (1+2*Z1 / Rf) of the average amount of the signal VIN at the drive electrode TX, and the gain of the signal amplification circuit 100 of this application is the gain of the change in the signal VIN at the drive electrode TX. Figure 15 The circuit shown has the same gain for the change in voltage VIN of the driving electrode TX.

[0103] According to formulas 19 and 20, the feedback circuit can reduce the gain of the signal amplifier circuit on the noise in the signal VIN of the drive electrode TX, reduce the proportion of common noise in the output signal of the signal amplifier circuit, and reduce the influence of the noise in the signal VIN of the drive electrode TX on the output signal of the signal amplifier circuit. Furthermore, it avoids excessive noise causing output saturation of the detection operational amplifier, which in turn prevents the detection capacitor Cs and / or Cc from being detected.

[0104] As can be seen from formulas 19 and 20, the attenuation coefficient of the gain of the signal amplification circuit 100 of this application for the average amount of the signal VIN on the driving electrode TX is 1 / (1+2*Z1 / Rf). Therefore, the gain of the signal amplification circuit against common noise can be adjusted according to the actual scenario by adjusting one or more of the following: the gain of the detection operational amplifier, the size of the feedback resistor 145, and the equivalent impedance Z1 of the first feedback path 111, to meet the scenario requirements.

[0105] This application addresses signal amplification circuits without feedback circuits and... Figure 6 The signal amplifier circuit 100 was simulated and compared. Figure 15 A circuit diagram of a signal amplifier circuit for comparison is shown. Simulation results are as follows. Figures 8A-8B to Figure 11A-11B As shown. Figures 8A-8B and Figures 9A-9B for Figure 15 The simulation results of the signal amplification circuit shown are presented. Figures 10A-10B and Figure 11A-11B for Figure 6 The simulation results for the signal amplification circuit 100 are shown. In the simulation, the coding frequency of the drive signal provided by the drive circuit 300 is 210.94 kHz. Figure 15 The equivalent impedance ZIN in the signal amplifier circuit shown Figure 6 The equivalent impedance ZIN of the signal amplifier circuit 100 shown is equal. Figure 15 The equivalent impedance Z1 in the signal amplifier circuit shown is... Figure 6 The equivalent impedance Z1 of the signal amplifier circuit 100 shown is equal. Figure 15 The equivalent impedance Z2 in the signal amplifier circuit shown is Figure 6 The equivalent impedance Z2 of the signal amplifier circuit 100 shown is equal. Figure 15 The equivalent impedance Z3 in the signal amplifier circuit shown is... Figure 6 The equivalent impedance Z3 of the signal amplifier circuit 100 shown is the same.

[0106] Figure 8A yes Figure 15 The time-domain plot of the output signal of the detection channel without finger touch in the signal amplification circuit shown. Figure 8B yes Figure 15 The signal amplification circuit shown has a time-domain diagram of the output signal of the finger touch detection channel. Figure 9A yes Figure 15 The frequency domain diagram of the detection channel without finger touch in the signal amplification circuit shown is shown. Figure 9B yes Figure 15 The frequency domain diagram of the signal amplification circuit shown has a finger touch detection channel. Figure 8A and 8BThe horizontal axis represents time, and the vertical axis represents the amplitude of the amplified signal output by the operational amplifier. Figure 9A and 9B The horizontal axis represents frequency, and the vertical axis represents the amplitude of the amplified signal output by the operational amplifier. For example... Figure 9A As shown, at a coding frequency of 210.94kHz, the amplitude of the amplified signal output by the operational amplifier of the detection channel without finger touch is 402.25mV, while the amplitude of the amplified signal output by the operational amplifier of the detection channel with finger touch is 397.16mV. The difference Δ between the two is 5.1mV, which represents the effect of touch on the coupling capacitance. Touch causes a change in the coupling capacitance, which in turn causes a change in the equivalent impedance ZIN. The change in the equivalent impedance ZIN causes a change in the gain of the signal amplification circuit on the signal VIN at the drive electrode TX.

[0107] Figures 10A-10B and Figure 11A-11B It shows Figure 6 The output signal of the signal amplification circuit 100 shown. Specifically, Figure 10A This is a time-domain plot of the output signal of the detection channel in the signal amplification circuit 100 when there is no finger touch. Figure 10B This is a time-domain plot of the output signal of the finger touch detection channel in the signal amplification circuit 100. Figure 11A This is a frequency domain diagram of the output signal of the detection channel in the signal amplification circuit 100 when there is no finger touch. Figure 11B This is the frequency domain diagram of the output signal of the finger touch detection channel in the signal amplifier circuit 100. In the simulation of the signal amplifier circuit 100, the equivalent impedance Z1 and the feedback resistor 145 are set to be equal.

[0108] like Figure 8A and 8B As shown in the time-domain diagram, Figure 15 The peak value of the output signal of the signal amplifier circuit shown is approximately ±1.7V. For example... Figure 10A and 10B As shown in the time-domain diagram, Figure 6 The peak value of the amplified signal output from the operational amplifier of the signal amplification circuit 100 shown is approximately ±650mV. Compared to Figure 15 The signal amplification circuit shown is Figure 6 The amplified signal output from the operational amplifier shown is attenuated overall. For the same amount of noise, Figure 15 The detection operational amplifier shown is compared to Figure 6 The operational amplifier shown is more prone to output saturation.

[0109] like Figure 11A and 11BAs shown, at a coding frequency of 210.94kHz, the amplitude of the amplified signal output by the operational amplifier of the detection channel without finger touch is 137.439mV, while the amplitude of the amplified signal output by the operational amplifier of the detection channel with finger touch is 132.906mV, with a difference Δ of 4.5mV. This difference Δ and Figure 15 The difference Δ between the signal amplification circuits without feedback is close. Based on the differences between the amplified signals of the outputs of multiple detection operational amplifiers 1101-110n, it is possible to determine which coupling capacitors are affected by the touch, and thus determine the touch position.

[0110] Combination Figures 8A-8B and Figures 10A-10B The time-domain plot, compared to Figure 15 The signal amplification circuit in the middle, Figure 6 The amplified signal of the operational amplifier in the detection circuit was attenuated by approximately 60%. Combined with... Figures 9A-9B and Figure 11A-11B The time-domain plot, compared to Figure 15 The signal amplification circuit in the middle, Figure 6 The difference Δ is attenuated by only 11%. As indicated by equations 19 and 20, feedback circuit 14 attenuates the gain of the detection amplifier on the average amount in the input signal VIN of the drive electrode TX, but the gain attenuation of the detection amplifier on the variation amount in the input signal VIN of the drive electrode TX is minimal. Therefore, the attenuation of the difference Δ is minimal.

[0111] Figure 90A-9B and Figure 11A-11B The frequency domain plots all include multiple peaks. The peak corresponding to the coding frequency of the drive signal provided by the drive circuit 300 (210.94kHz) indicates the amplitude of the useful drive signal, while the peaks corresponding to other frequencies represent the influence of noise. Compare Figures 90A-9B and... Figure 11A-11B , Figure 6 The noise peak corresponding to the output signal of the signal amplifier circuit 100 is less than Figure 15 The noise peak is removed from the output signal of the signal amplifier circuit. Therefore, the interference caused by noise is reduced, and the harmonic components introduced by noise are also attenuated.

[0112] In summary, the first averaging circuit 120 obtains the average voltage VOP_AVERAGE of multiple first amplified signals VOP1-VOPn, the second averaging circuit 130 obtains the average voltage VON_AVERAGE of multiple second amplified signals VON1-VONn, and the feedback operational amplifier 140 obtains the feedback voltage Vf based on the average voltages VON_AVERAGE and VOP_AVERAGE. The feedback resistor 145 converts the feedback voltage Vf into a feedback current. This feedback current is fed back to the first input terminal N1 of the detection operational amplifier, reducing the amplitude of the common noise in the first and second amplified signals of the detection operational amplifier, thus reducing the impact of the common noise on the signal amplification circuit. Furthermore, through feedback, excessive common noise can prevent the output of the detection operational amplifier from saturating.

[0113] Figure 12 This is a circuit diagram of another signal amplification circuit according to an embodiment of this application. Figure 12 As shown, the signal amplification circuit 100 includes: multiple detection operational amplifiers 1101-110n, a second averaging circuit 130, a feedback operational amplifier 141, and multiple feedback resistors 145. Figure 12 In the diagram, C11-C1n represent the driving electrode TX and the detection electrodes RX1-RX, respectively. n The coupling capacitors between them, VIP1-VIPn are the voltages at the first input terminal N1 of multiple detection operational amplifiers 1101-110n.

[0114] Each detection operational amplifier includes a first input terminal N1, a second input terminal N2, a first output terminal O1, and a second output terminal O2. The first input terminal N1 is connected to the corresponding detection electrode TX, and the second input terminal N2 is connected to the terminal providing the common-mode voltage VCM. One of the first input terminals N1 and N2 is a non-inverting input, and the other is an inverting input. One of the first output terminals O1 and O2 is an inverting output, and the other is a non-inverting output. The first output terminal O1 outputs a first amplified signal, and the second output terminal O2 outputs a second amplified signal. Both the first and second amplified signals are amplified signals of the voltage difference between the first and second input terminals N1 and N2, and they are inverted. The first output terminal O1 and the second output terminal O2 of the detection operational amplifiers 1101-110n are connected to other circuits, such as filter circuits or ADC circuits.

[0115] The second averaging circuit 130 is connected to the second output terminal O2 of a plurality of detection operational amplifiers 1101-110n, and is used to obtain the average voltage VON_AVERAGE of the plurality of second amplified signals VON1-VONn of the plurality of detection operational amplifiers 1101-110n. The second averaging circuit 130 includes, for example, a plurality of resistors, one end of which is connected to the second output terminal O2 of the corresponding detection operational amplifier, and the other end of which is connected to the output terminal of the second averaging circuit 130.

[0116] The feedback operational amplifier 141 provides a feedback voltage Vf that is proportional to the average voltage VON_AVERAGE. The feedback voltage Vf is equal to a * VON_AVERAGE, where a is the gain of the feedback operational amplifier 141. For example, if the gain a of the feedback operational amplifier 141 is 2, the feedback voltage Vf is: Vf = 2 * VON_AVERAGE.

[0117] Feedback resistor 145 is connected between the output of feedback operational amplifier 141 and the first input N1 of the corresponding detection operational amplifier. Feedback resistor 145 is used to convert the feedback voltage Vf into current.

[0118] The feedback voltage provided by the feedback operational amplifier 141 is, for example, 2*VON_AVERAGE. Figure 12 The signal amplification circuit shown can also be analyzed according to formula 1-20, and can also be implemented. Figure 6 The signal amplifier circuit shown has the following functions: Figure 6 The effect of the signal amplification circuit shown is to reduce noise in the output signal of the signal amplification circuit and prevent output saturation of the operational amplifier.

[0119] Figure 13 This is a circuit diagram of another signal amplification circuit provided in an embodiment of this application. For example... Figure 13 As shown, the signal amplification circuit 100 includes: multiple detection operational amplifiers 1101-110n, a first averaging circuit 120, a feedback operational amplifier 142, and multiple feedback resistors 145. Figure 13 In the diagram, C11-C1n represent the driving electrode TX and the detection electrodes RX1-RX, respectively. n The coupling capacitors between them, VIP1-VIPn are the voltages at the first input terminal N1 of multiple detection operational amplifiers 1101-110n.

[0120] Each detection operational amplifier includes a first input terminal N1, a second input terminal N2, a first output terminal O1, and a second output terminal O2. The first input terminal N1 is connected to the corresponding detection electrode TX, and the second input terminal N2 is connected to the terminal providing the common-mode voltage VCM. One of the first input terminals N1 and N2 is a non-inverting input, and the other is an inverting input. One of the first output terminals O1 and O2 is an inverting output, and the other is a non-inverting output. The first output terminal O1 outputs a first amplified signal, and the second output terminal O2 outputs a second amplified signal. Both the first and second amplified signals are amplified signals of the voltage difference between the first and second input terminals N1 and N2, and they are inverted. The first output terminal O1 and the second output terminal O2 of the detection operational amplifiers 1101-110n are connected to other circuits, such as filter circuits or ADC circuits.

[0121] The first averaging circuit 120 is connected to the first output terminal O1 of a plurality of detection operational amplifiers 1101-110n, and is used to obtain the average voltage VOP_AVERAGE of a plurality of first amplified signals VOP1-VOPn of the plurality of detection operational amplifiers 1101-110n. The first averaging circuit 120 includes, for example, a plurality of resistors, one end of which is connected to the first output terminal O1 of the corresponding detection operational amplifier, and the second end of which is connected to the output terminal of the first averaging circuit 120.

[0122] The feedback operational amplifier 142 provides a feedback voltage Vf that is proportional to the average voltage VOP_AVERAGE. The feedback voltage Vf is equal to b * VOP_AVERAGE, where b is the gain of the feedback operational amplifier 142. For example, if the gain b of the feedback operational amplifier 142 is -2, then the feedback voltage Vf is: Vf = -2 * VOP_AVERAGE = 2 * VON_AVERAGE.

[0123] Feedback resistor 145 is connected between the output of feedback operational amplifier 142 and the first input N1 of the corresponding detection operational amplifier. Feedback resistor 145 is used to convert the feedback voltage Vf into current.

[0124] The feedback voltage provided by the feedback operational amplifier 142 is, for example, 2*VON_AVERAGE. Figure 13 The signal amplification circuit shown can be analyzed according to formula 1-20, and can also be implemented. Figure 6 The signal amplifier circuit shown has the following functions: Figure 6 The effect of the signal amplification circuit shown is to reduce noise in the output signal of the signal amplification circuit and prevent output saturation of the operational amplifier.

[0125] Figure 14This is a circuit diagram of another signal amplification circuit provided in an embodiment of this application. For example... Figure 14 As shown, the signal amplification circuit 100 includes: multiple detection operational amplifiers 1101-110n, a third averaging circuit 150, a feedback operational amplifier 143, and multiple feedback resistors 145. Figure 14 In the diagram, C11-C1n represent the driving electrode TX and the detection electrodes RX1-RX, respectively. n The coupling capacitors between them, VIP1-VIPn are the voltages at the first input terminal N1 of the multiple detection operational amplifiers 1101-110n. In this embodiment, the detection operational amplifiers are single-output operational amplifiers.

[0126] The operational amplifiers 1101-110n all include a first input terminal N1, a second input terminal N2, and an output terminal O. The first input terminal N1 is connected to the corresponding detection electrode TX, and the second input terminal N2 is connected to the common-mode voltage VCM. The first input terminal N1 is, for example, an inverting input terminal, and the second input terminal N2 is, for example, a non-inverting input terminal. The output terminal O of the operational amplifiers 1101-110n outputs an amplified signal VO1-VOn. The amplified signal is either in phase or out of phase with the voltage at the first input terminal N1. The signal amplification circuit also includes a third feedback path 113. The third feedback path 113 is located between the output terminal O of the operational amplifier and the first input terminal N1. The third feedback path 113 includes a resistor and / or a capacitor. For example, the third feedback path 113 includes a feedback capacitor located between the output terminal O and the second input terminal N2. The driving electrode TX and the detection electrode RX are connected. j Coupling capacitance C1 between j The circuit consisting of operational amplifier 110j and third feedback path 113 amplifies the signal VIN on the drive electrode TX, where 1 ≤ j ≤ n. The amplification factor is related to the coupling capacitor C1. j Related. When touched, it causes coupling capacitance C1. j When the signal changes, the amplified signal output by the operational amplifier 110j is detected.

[0127] The third averaging circuit 150 is used to obtain the average voltage VO_AVERAGE of the multiple amplified signals VO1-VOn of the multiple detection operational amplifiers 1101-110n. The third averaging circuit 150 includes, for example, multiple resistors, one end of which is connected to the output terminal O of the corresponding detection operational amplifier, and the other end of which is connected to the output terminal of the third averaging circuit 150.

[0128] The feedback operational amplifier 143 is used to provide a feedback voltage Vf that is proportional to the average voltage VO_AVERAGE. If the gain of the feedback operational amplifier 143 is, for example, 2, then Vf = 2 * VO_AVERAGE.

[0129] The feedback resistor 145 is connected between the output of the feedback operational amplifier 143 and the first input N1 of the corresponding detection operational amplifier.

[0130] Figure 14 The signal amplification circuit shown can also achieve this. Figure 6 The signal amplifier circuit shown has the following functions: Figure 6 The effect of the signal amplification circuit shown is to reduce noise in the output signal of the signal amplification circuit and prevent output saturation of the operational amplifier.

[0131] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A signal amplification circuit, characterized in that, Applied to a touchscreen, the touchscreen includes multiple detection electrodes, and the signal amplification circuit is used to amplify the detection signals from the detection electrodes. The signal amplification circuit includes: Multiple operational amplifiers for detection, each operational amplifier including a first input terminal, a second input terminal, a first output terminal, and a second output terminal. The first input terminal is connected to a corresponding detection electrode, the second input terminal is connected to a common-mode voltage, the first output terminal outputs a first amplified signal, and the second output terminal outputs a second amplified signal. The first amplified signal and the second amplified signal are inverted. A feedback circuit includes multiple first input terminals and multiple second input terminals. The multiple first input terminals of the feedback circuit are respectively connected to the first output terminals of multiple detection operational amplifiers, and the multiple second input terminals of the feedback circuit are respectively connected to the second output terminals of the multiple detection operational amplifiers. The feedback circuit is used to generate a feedback signal based on the first amplified signal and the second amplified signal, and to provide the feedback signal to the first input terminals of the multiple detection operational amplifiers. The feedback circuit includes: A first averaging circuit is connected to the first output terminal of the plurality of detection operational amplifiers and is used to average the first amplified signals of the plurality of detection operational amplifiers to obtain a first average voltage. A second averaging circuit, connected to the second output terminals of the plurality of detection operational amplifiers, is used to average the second amplified signals from the plurality of detection operational amplifiers to obtain a second average voltage; and A feedback operational amplifier receives the first average voltage and the second average voltage, and outputs a feedback voltage; The feedback voltage is proportional to the voltage difference between the first average voltage and the second average voltage.

2. The signal amplification circuit according to claim 1, characterized in that, The feedback circuit also includes: Multiple feedback resistors are connected between the output terminal of the feedback operational amplifier and the first input terminal of the detection operational amplifier, and are used to output a feedback current based on the feedback voltage, wherein the feedback current is the feedback signal.

3. The signal amplification circuit according to claim 1, characterized in that, The feedback operational amplifier is a differential operational amplifier, which is used to perform the subtraction of the second average voltage and the first average voltage.

4. The signal amplification circuit according to any one of claims 1-3, characterized in that, The signal amplification circuit further includes a first feedback path and a second feedback path. The first feedback path is disposed between the first input terminal and the second output terminal of the detection operational amplifier, and the second feedback path is disposed between the second input terminal and the first output terminal of the detection operational amplifier.

5. The signal amplification circuit according to claim 4, characterized in that, The detection operational amplifier has a first input terminal that is non-inverting, a second input terminal that is inverting, a first output terminal that is non-inverting, and a second output terminal that is inverting; or, the detection operational amplifier has a first input terminal that is inverting, a second input terminal that is non-inverting, a first output terminal that is inverting, and a second output terminal that is non-inverting.

6. A signal amplification circuit, characterized in that, Applied to a touchscreen, the touchscreen including multiple detection electrodes, the signal amplification circuit includes: Multiple detection operational amplifiers are provided, each detection operational amplifier including a first input terminal, a second input terminal, and an output terminal. The first input terminal is connected to the corresponding detection electrode, the second input terminal is connected to a common-mode voltage, and the output terminal outputs an amplified signal. A third averaging circuit is used to obtain the average voltage of the multiple amplified signals of the multiple detection operational amplifiers; A feedback operational amplifier for providing a feedback voltage proportional to the average voltage of the plurality of amplified signals; and Multiple feedback resistors are connected between the output of the feedback operational amplifier and the first input of the detection operational amplifier.

7. The signal amplification circuit according to claim 6, characterized in that, The signal amplification circuit further includes a third feedback path, which is disposed between the output terminal and the first input terminal of the detection operational amplifier.

8. A touch chip, characterized in that, Includes a signal amplification circuit according to any one of claims 1 to 7.

9. An electronic device, characterized in that, include: A touchscreen, the touchscreen including multiple detection electrodes; as well as According to claim 8, the signal amplification circuit of the touch chip is used to amplify the detection signal of the detection electrode.

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