A variable gain amplifier, use method and biological signal processing chip
By designing a variable gain amplifier in a biological signal processing chip, and dynamically adjusting the gain using variable gain amplifier circuit and detection control circuit, the problem that fixed gain cannot adapt to the difference in signal strength of different groups of people is solved, and the accuracy and resistance of signal processing are improved Interference capability.
Patent Information
- Application Number
- CN201910660360.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2019-05-31
- Filing Date
- 2019-07-22
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2039-07-22
AI Technical Summary
In existing biological signal processing chips, fixed amplification gain cannot adapt to the difference in signal intensity of different populations, resulting in signal distortion or saturation, especially when humans are moving inadequate anti-interference ability.
Design a variable gain amplifier, including a variable gain amplifier circuit and a detection control circuit, and according to the peak and pre-value of the input signal through the first and second variable gain control units, an operational amplifier circuit, a peak detection circuit and a gain controller Set the range to adjust the gain to achieve dynamic gain control.
It improves the response speed of the switching capacitor filter, reduces the time required for the circuit to enter stable operation, enhances the amplification and anti-interference ability of biological signals, and is suitable for signal acquisition in a wide range of people and motion states.
Smart Images
Figure CN110474612B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of integrated circuit technology, and in particular to a variable gain amplifier, a method of using it, and a biosignal processing chip. Background Technology
[0002] In recent years, with the popularization of wearable health devices, chips used for detecting and processing biosignals have broad development prospects. To better analyze human health status from biosignals, reducing signal distortion and enhancing anti-interference capabilities have become important design requirements for this type of chip. Biosignals collected by general sensors contain a large number of unwanted components, while the effective biosignal components usually account for a very small proportion of the total signal. Taking heart rate signals collected by the PPG detection method as an example, the effective component accounts for less than 10% of the total signal. Therefore, it is necessary to amplify the extracted biosignals. Due to the significant differences in signal intensity among different populations, amplifiers with fixed gain may not have a wide range of applications. If the gain is too low, it is not conducive to the sampling circuit accurately acquiring subtle biosignal feature points; if the gain is too high, it may lead to saturation distortion.
[0003] Meanwhile, many measurements occur during human movement, such as measuring heart rate while running. If the signal amplification gain is too high at this time, the noise in the passband caused by the movement will saturate, which will drown out the effective heart rate signal components.
[0004] Therefore, in order to accommodate a wider range of users and enhance the ability to resist motion interference, it is necessary to add a variable gain amplifier circuit to the biosignal processing chip. Summary of the Invention
[0005] To address at least one of the aforementioned problems, a first aspect of the present invention provides a variable gain amplifier, comprising a variable gain amplification circuit and a detection and control circuit, wherein...
[0006] The variable gain amplifier circuit includes a first variable gain control unit, a second variable gain control unit, and an operational amplifier circuit, used to amplify the input signal and output the amplified signal;
[0007] The detection and control circuit is used to detect the amplified signal, compare the peak value of the amplified signal with a preset range, and output gain control signals to adjust the first variable gain control unit and the second variable gain control unit to adjust the gain of the variable gain amplifier.
[0008] Furthermore, the variable gain amplifier circuit also includes a feedback capacitor.
[0009] Furthermore, the first variable gain control unit includes a sampling variable capacitor and four sampling switches;
[0010] The second variable gain control unit includes a feedback variable capacitor and four feedback switches.
[0011] Furthermore, the clock frequencies of the sampling switch and the feedback switch satisfy oversampling relative to the clock frequency of the input signal.
[0012] Furthermore, the detection and control circuit includes a peak detection circuit and a gain controller, wherein...
[0013] The peak detection circuit is used to detect the amplified signal and output the peak value of the amplified signal;
[0014] The gain controller is used to compare the peak value with the preset range, and output the gain control signal according to the comparison result to adjust the gain of the variable gain amplifier.
[0015] Furthermore, the gain controller includes a first comparator, a second comparator, and a gating controller, wherein...
[0016] The first comparator is used to compare the peak value with a preset first threshold and output a first comparison result;
[0017] The second comparator is used to compare the peak value with a preset second threshold and output a second comparison result;
[0018] The gating controller is used to output the gain control signal based on the first comparison result and the second comparison result to adjust the gain of the variable gain amplifier.
[0019] A second aspect of the present invention provides a method of using the variable gain amplifier described in the first aspect, comprising:
[0020] The variable gain amplifier circuit amplifies the input signal and outputs the amplified signal through a first variable gain control unit, a second variable gain control unit, and an operational amplifier circuit.
[0021] The detection control circuit detects the amplified signal, compares it with the peak value of the amplified signal and a preset range, and outputs a gain control signal to adjust the first variable gain control unit and the second variable gain control unit.
[0022] Furthermore, the first variable gain control unit includes a sampling variable capacitor and four sampling switches, and the second variable gain control unit includes a feedback variable capacitor and four feedback switches;
[0023] The method of use also includes:
[0024] The clock frequencies of the sampling switch and the feedback switch are oversampled relative to the clock frequency of the input signal.
[0025] Furthermore, the detection control circuit includes a peak detection circuit and a gain controller;
[0026] The detection and control circuit detects the amplified signal, compares the peak value of the amplified signal with a preset range, and outputs gain control signals to adjust the first and second variable gain control units. Specifically, this includes:
[0027] The peak detection circuit detects the amplified signal and outputs the peak value of the amplified signal;
[0028] The gain controller compares the peak value with the preset range and outputs the gain control signal based on the comparison result.
[0029] A third aspect of the present invention provides a biosignal processing chip, including the variable gain amplifier described in the first aspect.
[0030] The beneficial effects of this invention are as follows:
[0031] This invention addresses existing problems by providing a variable gain amplifier, a method of use, and a biosignal processing chip. Through the variable gain amplifier circuit and detection control circuit, it effectively improves the response speed of the switched capacitor filter, reduces the time required for the circuit to reach stable operation, and meets the requirements of biosignal processing. Attached Figure Description
[0032] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.
[0033] Figure 1 This illustrates a negative feedback closed-loop variable gain amplifier in the prior art;
[0034] Figure 2 This illustrates another negative feedback closed-loop variable gain amplifier in the prior art;
[0035] Figure 3 A block diagram of a variable gain amplifier according to an embodiment of the present invention is shown;
[0036] Figure 4 A circuit diagram of a variable gain amplifier according to an embodiment of the present invention is shown;
[0037] Figure 5 A circuit diagram of a variable gain amplifier according to another embodiment of the present invention is shown;
[0038] Figure 6 The gain linearity test results of the variable gain amplifier according to one embodiment of the present invention are shown;
[0039] Figure 7The test results of the spectral characteristics of the variable gain amplifier according to one embodiment of the present invention are shown.
[0040] Figure 8 A flowchart illustrating a method of using a variable gain amplifier according to an embodiment of the present invention is shown. Detailed Implementation
[0041] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.
[0042] Traditional open-loop gain-controlled amplifiers are widely used in the demodulation section of high-frequency or radio-frequency systems such as wireless receivers. However, their swing and distortion are difficult to meet the requirements of biological signal processing.
[0043] In existing technologies, closed-loop variable gain amplifiers typically utilize negative feedback techniques, such as... Figure 1 As shown, this is a closed-loop variable gain amplifier that uses a variable resistor R2 to implement negative feedback. The gain of this amplifier is: The gain is related to the resistance values of R1 and R2. Although the operational amplifier meets the requirements in terms of swing and distortion to a certain extent, it requires a strong resistive load capability, thus increasing power consumption and area cost. Figure 2 The image shows another closed-loop variable gain amplifier that utilizes negative feedback technology. The negative feedback is achieved by connecting a variable capacitor C2 and resistor R1 in parallel. The gain of this amplifier is: The gain is related to the resistance values of C1 and C2, and meeting the requirements in terms of swing and distortion to a certain extent is sufficient. Although this operational amplifier does not require resistive load capability, the feedback capacitor C2 and resistor R1 form a high-pass characteristic. To meet the low-frequency requirements of biological signals, larger capacitor and resistor values are needed, thus reducing accuracy and increasing chip cost. Furthermore, Figure 1 and Figure 2 The closed-loop variable gain amplifier shown can only provide a gain greater than 1, which is insufficient to meet the practical application requirements in biological signal processing.
[0044] To solve the above problems, such as Figure 3As shown, one embodiment of the present invention provides a variable gain amplifier, including a variable gain amplifier circuit and a detection control circuit. The variable gain amplifier circuit includes a first variable gain control unit, a second variable gain control unit, and an operational amplifier circuit, used to amplify an input signal and output an amplified signal. The detection control circuit is used to detect the amplified signal, compare the peak value of the amplified signal with a preset range, and output a gain control signal to adjust the gain of the first variable gain control unit and the second variable gain control unit to adjust the gain of the variable gain amplifier.
[0045] In a specific example, such as Figure 4 As shown, the variable gain amplifier includes a variable gain amplification circuit and a detection and control circuit, with the input signal being V. in The output signal is V out The variable gain amplifier circuit employs switched capacitor technology to adapt to the low-frequency characteristics of biological signals, adjusting the input signal V... in Amplify and output V out In this embodiment, the variable gain amplifier circuit includes a first variable gain control unit, a second variable gain control unit, and an operational amplifier circuit.
[0046] Considering the need to sample subtle feature points of the biological signal, in a preferred embodiment, the clock frequencies of the first variable gain control unit and the second variable gain control unit satisfy oversampling relative to the clock frequency of the input signal. That is, at a frequency much higher than the input signal V. in Sampling at frequencies more than twice the bandwidth can push quantization noise to higher frequencies. Using a low-pass filter with a higher cutoff frequency can avoid aliasing of the sampled signal, effectively improving signal resolution and reducing noise.
[0047] Specifically, in this embodiment, the sampling frequency f of the first variable gain control unit and the second variable gain control unit... clk The frequency of the input signal V in Ten times the frequency. The first variable gain control unit includes a sampling variable capacitor C1 and four sampling switches. The sampling variable capacitor C1 and the sampling switches form a non-inverting switching capacitor. The equivalent resistance of the non-inverting switching capacitor is:
[0048] Similarly, the second variable gain control unit includes a feedback variable capacitor C2 and four feedback switches. The feedback variable capacitor C2 and the feedback switches form an inverting switching capacitor. The equivalent resistance of the inverting switching capacitor is:
[0049] Considering that switched capacitors are prone to causing glitches, in a preferred embodiment, the variable gain amplifier circuit further includes a feedback capacitor. For example... Figure 4 As shown, the feedback capacitor C f Connecting it in parallel with an inverting switched capacitor can effectively reduce the glitches caused by the switched capacitor, thus improving the output signal V. out For a smoother transition, the transfer equation of the programmable gain control amplifier circuit is:
[0050]
[0051] The low-frequency gain of this programmable gain-controlled amplifier circuit is:
[0052]
[0053] Specifically, the -3dB bandwidth of this programmable gain-controlled amplifier circuit is:
[0054] In this embodiment, the amplified output signal V is controlled by a detection control circuit. out To perform the test, amplify the signal V. out The gain of the variable gain amplifier is adjusted by comparing it with a preset range and outputting a control signal based on the comparison result to adjust the gain control signals of the first variable gain control unit and the second variable gain control unit.
[0055] In a preferred embodiment, such as Figure 5 As shown, the detection control circuit includes a peak detection circuit and a gain controller. The peak detection circuit is used to detect the amplified signal and output the peak value of the amplified signal. The gain controller is used to compare the peak value with the preset range and output the gain control signal according to the comparison result to adjust the gain of the variable gain amplifier.
[0056] Specifically, the peak detection circuit detects the output voltage V. out The peak value is compared with a preset expected peak range, wherein the preset range sets a high-level upper limit V. CH and low level lower limit V CL The output voltage V out The peak values are respectively compared with V by a comparator. CH and V CL Perform the comparison and obtain the comparison result D i0 and D i1 D i0 and D i1An input gain controller generates a control signal DV to adjust the gain of the variable gain amplifier circuit. Specifically, the control signal DV is transmitted to the first variable gain control unit and the second variable gain control unit to adjust the sampling variable capacitor C1 and the feedback variable capacitor C2.
[0057] In a preferred embodiment, the gain controller includes a first comparator, a second comparator, and a gating controller, wherein the first comparator is used to compare the peak value with a preset first threshold and output a first comparison result; the second comparator is used to compare the peak value with a preset second threshold and output a second comparison result; and the gating controller is used to output the gain control signal according to the first comparison result and the second comparison result to adjust the gain of the variable gain amplifier.
[0058] Even if the gain control function is implemented using a first comparator, a second comparator, and a conventional controller: the first threshold of the first comparator is V. CH The output voltage V out peak value and V CH Perform the comparison and output the first comparison result D. i0 Similarly, the second threshold of the second comparator is V. CL The output voltage V out peak value and V CL Perform the comparison and output the first comparison result D. i1 D i0 and D i1 Input gating controller, the gating controller according to D i0 and D i1 Output gain control signal DV.
[0059] If the output voltage V out The peak value is greater than V CH Then, a control signal DV is generated and C1 and C2 are controlled. The gain of the variable gain amplifier is reduced according to formulas (1) and (2). If the peak value of the output voltage Vout is less than V CL Then, a control signal DV is generated and C1 and C2 are controlled. The gain of the variable gain amplifier is increased according to formulas (1) and (2). If the peak value of the output voltage Vout is at V CH and V CL Between these points, the current gain remains unchanged.
[0060] Using the variable gain amplifier provided in this embodiment, such as Figure 6As shown, the horizontal axis represents the control codes corresponding to different capacitance values of the variable capacitor, and the vertical axis represents the gain. The graph shows that when the variable capacitor value is different, and the frequency of the input biological signal is 0.5Hz, the linearity of the gain of this variable gain amplifier reaches 0.9998, which meets the amplification requirements of the biological signal. Furthermore, as... Figure 7 As shown in the figure, the horizontal axis represents the frequency value of the input biological signal, and the vertical axis represents the gain. It can be seen from the figure that the gain curves with different values of the variable capacitor have good spectral characteristics in the low-frequency field. That is, the variable gain amplifier has good spectral characteristics in the low-frequency field, which is suitable for biological signals. It can provide appropriate gain for the amplification of biological signals, reduce signal distortion, and enhance anti-interference ability.
[0061] Corresponding to the variable gain amplifier provided in the above embodiments, one embodiment of this application also provides a method of using the above variable gain amplifier. Since the method of use provided in this application corresponds to the variable gain amplifier provided in the above embodiments, the method of use provided in this embodiment is also applicable to the foregoing implementation methods, and will not be described in detail in this embodiment.
[0062] like Figure 8 As shown, one embodiment of this application also provides a method of using the above-mentioned variable gain amplifier, including: a variable gain amplifier circuit amplifies an input signal and outputs an amplified signal through a first variable gain control unit, a second variable gain control unit, and an operational amplifier circuit; a detection control circuit detects the amplified signal, compares it with the peak value of the amplified signal and a preset range, and outputs a gain control signal to adjust the first variable gain control unit and the second variable gain control unit.
[0063] In an optional embodiment, the first variable gain control unit includes a sampling variable capacitor and four sampling switches, and the second variable gain control unit includes a feedback variable capacitor and four feedback switches; the method of use further includes: the clock frequencies of the sampling switches and feedback switches satisfy oversampling relative to the clock frequency of the input signal.
[0064] In another optional embodiment, the detection control circuit includes a peak detection circuit and a gain controller; the detection control circuit detects the amplified signal, compares the peak value of the amplified signal with a preset range, and outputs a gain control signal to adjust the first variable gain control unit and the second variable gain control unit. Specifically, the peak detection circuit detects the amplified signal and outputs the peak value of the amplified signal; the gain controller compares the peak value with the preset range and outputs the gain control signal based on the comparison result.
[0065] One embodiment of this application also provides a biosignal processing chip, including the aforementioned variable gain amplifier. It is capable of analyzing the health status of the human body based on biosignals, reducing signal distortion, and enhancing anti-interference capabilities.
[0066] This invention addresses existing problems by providing a variable gain amplifier, a method of use, and a biosignal processing chip. Through the variable gain amplifier circuit and detection control circuit, it effectively improves the response speed of the switched capacitor filter, reduces the time required for the circuit to reach stable operation, and meets the requirements of biosignal processing.
[0067] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.
Claims
1. A variable gain amplifier, characterized in that: It includes a variable gain amplifier circuit and a detection control circuit, wherein The variable gain amplifier circuit includes a first variable gain control unit, a second variable gain control unit and an operational amplifier circuit, which are used to amplify an input signal and output an amplified signal; the first variable gain control unit includes a sampling variable capacitor and four sampling switches, and the sampling variable capacitor and the sampling switch form a common-phase switch capacitor; the second variable gain control unit includes a feedback variable capacitor and four feedback switches, and the feedback variable capacitor and the feedback switch form an anti-phase switch capacitor; The clock frequencies of the sampling switch and the feedback switch satisfy oversampling relative to the clock frequency of the input signal; The variable gain amplifier circuit further includes a feedback capacitor, which is connected in parallel with the inverting switch capacitor; The detection control circuit is used to detect the amplified signal, compare the peak value of the amplified signal with a preset range, and output a gain control signal for adjusting the first variable gain control unit and the second variable gain control unit to adjust the gain of the variable gain amplifier.
2. The variable gain amplifier according to claim 1, characterized in that: The detection control circuit includes a peak detection circuit and a gain controller, wherein The peak detection circuit is used to detect the amplified signal and output the peak value of the amplified signal; The gain controller is used to compare the peak value with the preset range, and output the gain control signal to adjust the gain of the variable gain amplifier according to the comparison result.
3. The variable gain amplifier according to claim 2, characterized in that: The gain controller includes a first comparator, a second comparator and a gating controller, wherein The first comparator is used to compare the peak value with a preset first threshold value and output a first comparison result; The second comparator is used to compare the peak value with a preset second threshold value and output a second comparison result; The gating controller is used to output the gain control signal to adjust the gain of the variable gain amplifier according to the first comparison result and the second comparison result.
4. A method for using the variable gain amplifier according to any one of claims 1 to 3, characterized in that: include: The variable gain amplifier circuit amplifies the input signal through the first variable gain control unit, the second variable gain control unit and the operational amplifier circuit and outputs the amplified signal; The detection control circuit detects the amplified signal, compares the peak value of the amplified signal with a preset range, and outputs a gain control signal for adjusting the first variable gain control unit and the second variable gain control unit; The first variable gain control unit includes a sampling variable capacitor and four sampling switches, wherein the sampling variable capacitor and the sampling switch form a common-phase switch capacitor; the second variable gain control unit includes a feedback variable capacitor and four feedback switches, wherein the feedback variable capacitor and the feedback switch form a counter-phase switch capacitor; The variable gain amplifier circuit further includes a feedback capacitor, which is connected in parallel with the inverting switch capacitor; The method of use also includes: The clock frequencies of the sampling switch and the feedback switch satisfy oversampling relative to the clock frequency of the input signal.
5. The method of use according to claim 4, characterized in that: The detection control circuit includes a peak detection circuit and a gain controller; The detection control circuit detects the amplified signal, compares the peak value of the amplified signal with a preset range, and outputs a gain control signal for adjusting the first variable gain control unit and the second variable gain control unit, specifically including: The peak detection circuit detects the amplified signal and outputs the peak value of the amplified signal; The gain controller compares the peak value with the preset range, and outputs the gain control signal according to the comparison result.
6. A biosignal processing chip, characterized in that: A variable gain amplifier comprising the variable gain amplifier according to any one of claims 1 to 3.