Gm-C filter device and calibration circuit and calibration method thereof

Abstract

The present application discloses a Gm-C filter device and a calibration circuit and a calibration method thereof. The calibration circuit includes: a pulse generation module for generating a pulse signal whose pulse width is proportional to the capacitance value of a reference capacitor; a counter for counting the pulse width of the pulse signal using a system clock to obtain a count value; a transconductance amplifier for converting an input voltage signal into a first current and a second current that are inversely phased to each other; and a calibration module for generating a transconductance control signal according to the current signal corresponding to the first current, the second current and the count value, and at the same time, the control end of the transconductance amplifier receives the transconductance control signal as a feedback signal, and the transconductance amplifier adjusts its own transconductance value according to the transconductance control signal. The calibration circuit generates a calibrated transconductance control signal based on the feedback principle of the transconductance amplifier, which can simplify the circuit structure and improve the stability of the calibration circuit.

Description

Technical Field

[0001] The present application relates to filter technology, and more specifically, to a Gm-C filter device and a calibration circuit and a calibration method thereof. Background Art

[0002] Active filters are circuit units used to filter out useless signals in various signal processing links. According to different circuit structures, active filters can be divided into RC filters and Gm-C filters. RC filters are composed of operational amplifiers, resistors and capacitors, and the frequency characteristics are determined by the product of resistance and capacitance R*C. Gm-C filters are composed of transconductance amplifiers and capacitors, and the frequency characteristics are determined by the ratio of transconductance and capacitance Gm / C. Gm-C filters not only have the advantages of low power consumption, high speed and good high-frequency characteristics, but are also suitable for integration into chips.

[0003] The frequency characteristics of the Gm-C filter are affected by the discreteness of the integrated circuit process. Even if different chips of the same design are used, the ratio of the transconductance value to the capacitance value Gm / C will differ by dozens of percentages due to differences in process deviation, ambient temperature, operating voltage and other factors. Therefore, it is necessary to design the Gm-C filter as an adjustable bandwidth, and calibrate its frequency characteristics to the required frequency range through an integrated calibration algorithm. The technology for realizing adjustable bandwidth in the Gm-C filter includes using a capacitor array to adjust the capacitance value C to achieve frequency tuning, and / or using a transconductance value to adjust the transconductance value Gm of the transconductance amplifier to achieve frequency tuning. Since the capacitor occupies a large chip area, the use of a capacitor array to achieve frequency tuning is not conducive to the miniaturization of the chip, and the application of the tuning method of adjusting the transconductance value of the transconductance amplifier in the Gm-C filter is more attractive.

[0004] However, the calibration circuit of the Gm-C filter needs to occupy additional chip area and generate additional power consumption and circuit cost. Summary of the invention

[0005] In view of the above problems, the object of the present invention is to provide a Gm-C filter device and a calibration circuit and a calibration method thereof, wherein a calibrated transconductance control signal is generated based on the feedback principle of a transconductance amplifier to simplify the circuit structure and improve the stability of the calibration circuit.

[0006] According to one aspect of the present invention, there is provided a calibration circuit for a Gm-C filter, for providing a calibrated transconductance control signal to the Gm-C filter, comprising: a pulse generating module, for generating a pulse signal whose pulse width is proportional to the capacitance value of a reference capacitor; a counter, connected to the pulse generating module, for counting the pulse width of the pulse signal using a system clock to obtain a count value; a transconductance amplifier, for converting an input voltage signal into a first current and a second current that are inversely phased to each other; and a calibration module, connected to the counter and the transconductance amplifier, for generating the transconductance control signal according to the first current, the second current and the count value, wherein a control end of the transconductance amplifier receives the transconductance control signal as a feedback signal, and the transconductance amplifier adjusts its own transconductance value according to the transconductance control signal.

[0007] Preferably, the calibration module includes: a first current branch, superimposing the first current with a current signal to obtain a first branch current, and the current signal is proportional to the count value; a second current branch, superimposing the second current with a third current to obtain a second branch current, and the third current is proportional to the current signal; a third resistor, located on the first current branch to generate a first voltage signal corresponding to the first branch current; a fourth resistor, located on the second current branch to generate a second voltage signal corresponding to the second branch current; and a first operational amplifier, wherein the inverting input terminal of the first operational amplifier receives the first voltage signal, the non-inverting input terminal receives the second voltage signal, and the output terminal provides the transconductance control signal.

[0008] Preferably, it also includes a first voltage generating module, which includes a first current source, a first resistor and a second current source connected in series in sequence, the first current source and the second current source provide reference currents equal to each other in the same direction, and the two ends of the first resistor are respectively connected to the non-inverting input terminal and the inverting input terminal of the transconductance amplifier to provide the input voltage signal.

[0009] Preferably, the first current branch comprises a third current source, the third current source is coupled with the first current source in a current mirror manner to generate the current signal, and a current proportionality coefficient between the current signal and the reference current is adjusted according to the count value.

[0010] Preferably, the current proportionality coefficient is equal to the count value.

[0011] Preferably, the second current branch comprises a fourth current source, the fourth current source is coupled with the third current source in a current mirror manner to generate the third current, and a current proportionality coefficient between the third current and the current signal is a fixed value.

[0012] Preferably, the pulse generating module comprises: a second operational amplifier and a third operational amplifier; a second resistor connected to the inverting input terminal of the second operational amplifier; a first switch and a reference capacitor connected in parallel between the inverting input terminal and the output terminal of the second operational amplifier; and a second switch connected between the output terminal of the third operational amplifier and ground, wherein the inverting input terminal of the second operational amplifier receives the first reference voltage via the second resistor, the non-inverting input terminal receives the second reference voltage, and the output terminal provides an intermediate signal, the inverting input terminal of the third operational amplifier is connected to the output terminal of the second operational amplifier to receive the intermediate signal, the non-inverting input terminal receives the third reference voltage, and the output terminal provides the pulse signal.

[0013] Preferably, the second operational amplifier integrates the current starting from the second reference voltage to generate a triangular wave signal as the intermediate signal, and the first switch and the second switch are in an off state during the integration period.

[0014] Preferably, a resistance ratio of the second resistor to the first resistor is a predetermined value.

[0015] Preferably, it also includes a second voltage generating module, which includes a fifth current source, a seventh resistor, a sixth resistor and a fifth resistor connected in series between the power supply terminal and the ground, wherein the first reference voltage is generated across the fifth resistor, the second reference voltage is generated across the fifth resistor and the sixth resistor, and the third reference voltage is generated across the fifth resistor, the sixth resistor and the seventh resistor.

[0016] Preferably, the control end of the transconductance amplifier receives the transconductance control signal for feedback adjustment of the transconductance value of the transconductance amplifier, so that the ratio of the transconductance value of the transconductance amplifier itself to the capacitance value of the reference capacitor is a fixed value.

[0017] Preferably, when the calibration circuit is started, the pulse generating module and the counter are enabled to obtain and store the count value, and then the pulse generating module and the counter are stopped.

[0018] Preferably, the calibration module receives a digital value obtained by scaling the count value up or down to achieve digital control of the bandwidth of the Gm-C filter.

[0019] According to another aspect of the present invention, there is provided a calibration method for a Gm-C filter, for providing a calibrated transconductance control signal to the Gm-C filter, comprising: generating a pulse signal having a pulse width proportional to the capacitance value of a reference capacitor; using a system clock to count the pulse width of the pulse signal to obtain a count value; using a transconductance amplifier to convert an input voltage signal into a first current and a second current that are inverted to each other; generating the transconductance control signal according to the first current, the second current and the count value; and providing the transconductance control signal as a feedback signal to a control terminal of the transconductance amplifier to adjust the transconductance value of the transconductance amplifier.

[0020] Preferably, the step of generating the transconductance control signal includes: superimposing the first current with a current signal to obtain a first branch current, the current signal being proportional to the count value; superimposing the second current with a third current to obtain a second branch current, the third current being proportional to the current signal; generating a first voltage signal corresponding to the first branch current; generating a second voltage signal corresponding to the second branch current; and differentially amplifying the first voltage signal and the second voltage signal to obtain the transconductance control signal.

[0021] Preferably, a current proportionality coefficient between the current signal and a reference current is adjusted according to the count value.

[0022] Preferably, the current proportionality coefficient is equal to the count value.

[0023] Preferably, a current proportionality coefficient between the third current and the current signal is a fixed value.

[0024] Preferably, the step of generating the pulse signal comprises: integrating the current starting from the second reference voltage to generate a triangular wave signal as an intermediate signal; and comparing the triangular wave signal with a third reference voltage to generate the pulse signal.

[0025] Preferably, the steps of integrating the current starting from the second reference voltage and comparing the triangular wave signal with the third reference voltage are repeated to generate multiple triangular wave signals and multiple pulse signals, and the pulse widths of the multiple pulse signals are counted and averaged using the system clock to obtain the count value.

[0026] Preferably, the control end of the transconductance amplifier receives the transconductance control signal for feedback adjustment of the transconductance value of the transconductance amplifier, so that the ratio of the transconductance value of the transconductance amplifier itself to the capacitance value of the reference capacitor is a fixed value.

[0027] Preferably, the steps of generating a pulse signal and counting the pulse signal are performed when the calibration circuit is started, and then the count value is stored, and the steps of generating a pulse signal and counting the pulse signal are stopped.

[0028] Preferably, the count value is scaled up or down to achieve digital control of the bandwidth of the Gm-C filter.

[0029] According to another aspect of the present invention, a Gm-C filtering device is provided, comprising: the calibration circuit mentioned above; and a Gm-C filter connected to the calibration circuit to receive a calibrated transconductance control signal.

[0030] Preferably, the Gm-C filter and the calibration circuit are integrated into a single chip.

[0031] According to the calibration circuit and calibration method of the above-mentioned embodiment, a current signal corresponding to the capacitance value of the reference capacitor is superimposed in the feedback loop of the transconductance amplifier, and based on the feedback principle of the transconductance amplifier, the ratio of the transconductance value of the transconductance amplifier to the capacitance value of the capacitor is maintained at a fixed value, thereby obtaining a transconductance control signal for Gm-C filter calibration. In the calibration circuit, for example, a single reference capacitor can be used without using a capacitor array, thereby simplifying the circuit structure and reducing the circuit area in the chip. In the calibration circuit, the role of the transconductance amplifier is to amplify the input voltage signal into a current signal, and there is no need to form a voltage-controlled oscillator with the capacitor. Therefore, the calibration circuit does not have the circuit complexity caused by the voltage-controlled oscillator and the problem of limiting the oscillation signal, thereby further simplifying the circuit structure and improving the stability of the calibration circuit.

[0032] In a preferred embodiment, the current proportionality coefficient between the current signal and the reference current is adjusted according to the count value. In the calibration circuit startup phase, after obtaining the count value, the count value is stored to stop the pulse generation module, thereby reducing the power consumption of the calibration circuit. Since the transconductance value of the transconductance amplifier is proportional to the count value, the digital control of the Gm-C filter bandwidth can be achieved by proportionally enlarging or reducing the count value.

[0033] The calibration circuit has the advantages of small circuit area, low power consumption, simple implementation, etc., and can be widely used in various signal processing circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings.

[0035] Figure 1 FIG. 4 is a schematic circuit block diagram of a Gm-C filter device according to the prior art.

[0036] Figure 2 A schematic circuit block diagram of a Gm-C filtering device according to an embodiment of the present invention is shown.

[0037] Figure 3 FIG. 4 is a detailed circuit diagram of a calibration circuit in a Gm-C filter device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by the same or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0039] Figure 1 A schematic circuit block diagram of a Gm-C filter device according to the prior art is shown. As shown in the figure, the Gm-C filter device 10 includes a Gm-C filter 11 and a calibration circuit 100. The calibration circuit 100 provides a transconductance control signal Vc to the Gm-C filter 11, and the transconductance control signal Vc is used to adjust the transconductance value of the transconductance amplifier in the Gm-C filter 11 to obtain a desired frequency range.

[0040] The calibration circuit 100 includes a plurality of transconductance amplifiers 101 , a frequency divider 102 , a phase frequency detector 103 , a charge pump 104 , a low pass filter 105 , and a plurality of capacitors C11 .

[0041] In the calibration circuit 100, a plurality of transconductance amplifiers 101 and a plurality of capacitors C11 are connected to form a voltage-controlled oscillator. A frequency divider 102, a phase frequency detector 103, a charge pump 104, and a low-pass filter 105 are connected to form a phase-locked circuit. After the loop is locked, the oscillation frequency of the voltage-controlled oscillator is the same as the frequency of the input clock signal of the phase frequency detector 103 in the phase-locked circuit. The voltage-controlled oscillator matches the transconductance amplifier and the capacitor in the Gm-C filter 11. Therefore, the frequency characteristic of the Gm-C filter 11 can be determined by the input clock signal of the phase frequency detector 103 in the calibration circuit 100.

[0042] The calibration circuit 100 according to the prior art adopts a voltage-controlled oscillator and a phase-locked circuit structure, which has the advantages of high calibration result accuracy and can be calibrated in real time according to the working environment, but has the disadvantages of being always working and consuming a lot of power. In addition, if the oscillation signal of the voltage-controlled oscillator is not limited, it may have a significant impact on the calibration result, so the stability of the calibration circuit 100 is poor.

[0043] Figure 2A schematic circuit block diagram of a Gm-C filter device according to an embodiment of the present invention is shown. As shown in the figure, the Gm-C filter device 20 includes a Gm-C filter 11 and a calibration circuit 200. The calibration circuit 200 provides a transconductance control signal Vc to the Gm-C filter 11, and the transconductance control signal Vc is used to adjust the transconductance value of the transconductance amplifier in the Gm-C filter 11 to obtain a desired frequency characteristic. Preferably, the Gm-C filter device 20 is a single chip, including the Gm-C filter 11 and the calibration circuit 200 integrated together.

[0044] The calibration circuit 200 includes a transconductance amplifier 201, a pulse generating module 202, a counter 203, and a calibration module 204. The input end of the transconductance amplifier 201 receives a constant input voltage signal Va, and converts the input voltage signal Va into a first current and a second current that are inversely phased to each other. The pulse generating module 202 generates a pulse signal Vrc whose pulse width is proportional to the capacitance value of the reference capacitor. The counter 203 counts the pulse signal Vrc using a system clock to obtain a count value N. The calibration module 204 is located on the feedback loop of the transconductance amplifier 201, and generates a transconductance control signal Vc according to the first current, the second current and the count value N. The control end of the transconductance amplifier 201 receives the transconductance control signal Vc as a feedback signal.

[0045] During the operation of the calibration circuit 200, the calibration module 204 converts the count value N into a current signal, and superimposes the current signal corresponding to the capacitance value of the reference capacitor in the feedback loop of the transconductance amplifier 201, so that the ratio of the transconductance value of the transconductance amplifier 201 to the capacitance value of the reference capacitor is maintained at a fixed value, thereby obtaining the transconductance control signal Vc for Gm-C filter calibration.

[0046] According to the calibration circuit 200 of this embodiment, the calibration circuit 200 maintains the ratio of the transconductance value of the transconductance amplifier 201 to the capacitance value of the reference capacitor as a fixed value based on the feedback principle. In the calibration circuit 200, for example, a single reference capacitor is used, and there is no need to use a capacitor array, so that the circuit structure can be simplified and the circuit area in the chip can be reduced. In the calibration circuit 200, the function of the transconductance amplifier 201 is to amplify the input voltage signal Va into a current signal, and there is no need to form a voltage-controlled oscillator with the capacitor. Therefore, the calibration circuit 200 does not have the circuit complexity caused by the voltage-controlled oscillator and the problem of limiting the oscillation signal, so that the circuit structure can be further simplified and the stability of the calibration circuit can be improved.

[0047] Figure 3Detailed circuit diagram of the calibration circuit in the Gm-C filter device according to the embodiment of the present invention is shown. As described above, the calibration circuit 200 includes a transconductance amplifier 201, a pulse generating module 202, a counter 203, and a calibration module 204. Further, the calibration circuit 200 also includes voltage generating modules 205 and 206.

[0048] The voltage generating module 205 includes a current source 221, a resistor R1 and a current source 222 which are sequentially connected in series between a power supply terminal and a ground. The current sources 221 and 222 provide equal constant currents Is. Both ends of the resistor R1 are respectively connected to the non-inverting input terminal and the inverting input terminal of the transconductance amplifier 201, thereby providing a constant input voltage signal Va=Is×Rv1 to the transconductance amplifier 201, wherein Rv1 represents the resistance value of the resistor R1.

[0049] The voltage generating module 206 includes a current source 225, a resistor R7, a resistor R6, and a resistor R5 which are sequentially connected in series between the power supply terminal and the ground. The current source 225 provides a constant current Ib, generates a reference voltage Vr1 at both ends of the resistor R5, generates a reference voltage Vr2 at both ends of the resistors R5 and R6, and generates a reference voltage Vr3 at both ends of the resistors R5, R6, and R7, and the reference voltages Vr1, Vr2, and Vr3 increase sequentially.

[0050] The same input terminal of the transconductance amplifier 201 receives a constant input voltage signal Va, and converts the input voltage signal Va into a first current I1 and a second current I2 which are inverted to each other.

[0051] The pulse generating module 202 is, for example, an RC oscillator, and includes operational amplifiers 212 and 213, switches S1 and S2, a resistor R2, and a capacitor C1. The inverting input terminal of the operational amplifier 212 receives a reference voltage Vr1 via the resistor R2, and the non-inverting input terminal receives a reference voltage Vr2, and the reference voltage Vr2 is greater than the reference voltage Vr1. The switch S1 and the capacitor C1 are connected in parallel between the output terminal and the inverting input terminal of the operational amplifier 212. The operational amplifier 212 acts as an integrator and provides an intermediate signal Vb at the output terminal. The non-inverting input terminal of the operational amplifier 213 receives a reference voltage Vr3, and the inverting input terminal receives the intermediate signal Vb. The output terminal of the operational amplifier 213 is grounded via the switch S2. The operational amplifier 213 compares the reference voltage Vr3 with the intermediate signal Vb, and provides a pulse signal Vrc at the output terminal.

[0052] The capacitor C1 in the pulse generating module 202 is used as a reference capacitor, which matches the capacitor in the Gm-C filter 11 , for example, 1 / 1000 of the capacitance value of the filter capacitor in the Gm-C filter 11 .

[0053] The first input terminal of the counter 203 receives the pulse signal Vrc, and the second input terminal receives the system clock CLK. The counter 203 uses the system clock CLK to count the pulse signal Vrc to obtain a count value N, and provides the count value N at the output terminal.

[0054] The calibration module 204 includes an operational amplifier 211, current sources 223 and 224, and resistors R3 and R4. The current source 223 and the resistor R3 are connected in series between the power supply terminal and the ground to form a first current branch. The current source 224 and the resistor R4 are connected in series between the power supply terminal and the ground to form a second current branch. The in-phase output terminal of the transconductance amplifier 201 is connected to the middle node of the current source 223 and the resistor R3 to provide a first current I1, and the inverting output terminal is connected to the middle node of the current source 224 and the resistor R4 to provide a second current I2. The current source 223 is coupled to the current source 221 in a current mirror manner, and the current proportional coefficient is the count value N, that is, it is adjusted accordingly according to the count value N. The current source 224 is coupled to the current source 223 in a current mirror manner, and the current proportional coefficient is a predetermined fixed value a. The superimposed current of the first current branch is equal to I11=N*Is+Is×Rv1×Gm, and a first voltage signal V1 is generated at both ends of the resistor R3. The superimposed current of the second current branch is equal to I12=a*N*Is-Is×Rv1×Gm, and a second voltage signal V2 is generated at both ends of the resistor R4. The inverting input terminal of the operational amplifier 211 is connected to the middle node of the current source 223 and the resistor R3 to receive the first voltage signal V1, the non-inverting input terminal is connected to the middle node of the current source 224 and the resistor R4 to receive the second voltage signal V2, and the output terminal provides a transconductance control signal Vc.

[0055] During the operation of the calibration circuit 200, when the pulse generating module 202 starts to work, the switches S1 and S2 are disconnected, the capacitor C1 is charged by the current of the feedback loop, the voltage at both ends gradually increases from zero, and the intermediate signal Vb provided by the output end of the operational amplifier 212 gradually increases from the reference voltage Vr2. When the intermediate signal Vb increases to the reference voltage Vr3, the switches S1 and S2 are closed, the capacitor C1 is discharged through the switch S1, the voltage at both ends returns to zero, and the intermediate signal Vb provided by the output end of the operational amplifier 212 decreases from the reference voltage Vr3 to the reference voltage Vr2.

[0056] During the operation of the pulse generating module 202, the intermediate signal Vb provided at the output terminal of the operational amplifier 212 is a single triangle wave signal. The operational amplifier 213 compares the reference voltage Vr3 with the intermediate signal Vb, and the pulse signal Vrc provided at the output terminal is a single pulse signal.

[0057] The pulse width T of the pulse signal Vrc is proportional to the product of the resistance value Rv2 of the resistor R2 and the capacitance value Cv1 of the capacitor C1, as shown in the following formula (1):

[0058] T=(Vr3-Vr2)×Cc1×Rr2 / (Vr2-Vr1)=k×Rv2×Cv1, (1)

[0059] Here, k is a proportionality coefficient associated with the reference voltages Vr1 to Vr3.

[0060] The counter 203 uses the system clock CLK to count the pulse signal Vrc to obtain a count value N, as shown in the following formula (2):

[0061] N=k×Rv2×Cv1 / T0 (2)

[0062] Wherein, T0 is the period of the system clock CLK.

[0063] In a further preferred embodiment, during the operation of the pulse generating module 202, the intermediate signal Vb provided at the output of the operational amplifier 212 is a plurality of triangular wave signals, and the pulse signal Vrc provided at the output of the operational amplifier 213 is a plurality of pulse signals. The counter 203 counts the plurality of pulse signals respectively and takes an average value to obtain the count value N, thereby improving stability.

[0064] During the operation of the calibration circuit 200, the calibration module 204 is located on the feedback loop of the transconductance amplifier 201, and generates a transconductance control signal Vc according to the first current I1, the second current I2 and the count value N. The control end of the transconductance amplifier 201 receives the transconductance control signal Vc as a feedback signal, and adjusts its own transconductance value Gm according to the transconductance control signal Vc. The result of the negative feedback of the operational amplifier 211 is V1=V2. The resistance values ​​of the resistors R3 and R4 are set to be equal to each other, then I11=I12, thereby obtaining the following equation (3),

[0065] N×Is+Is×Rv1×Gm=a×N×Is-Is×Rv1×Gm(3)

[0066] Furthermore, the following equation (4) can be obtained:

[0067] Gm=(a-1) / 2×N / Rv1(4)

[0068] Combining equations (2) and (4), we can obtain the following equation (5),

[0069] Gm / Cv1=k×(a-1) / (2×T0)×Rv2 / Rv1(5).

[0070] Based on the above equation (5), it can be known that if the resistance values ​​of the resistors R2 and R1 are set to a predetermined ratio, since the current proportionality coefficient a and the system clock period T0 are both process-independent quantities, the calibration circuit 200 can maintain the ratio of the transconductance value Gm of the transconductance amplifier 201 itself to the capacitance value Cv1 of the capacitor C1 at a fixed value.

[0071] In the calibration circuit 200, the transconductance control signal Vc generated by the calibration circuit 200 is provided to the Gm-C filter 11 for calibrating the transconductance value of the internal transconductance amplifier of the Gm-C filter 11, so that the frequency characteristic calibration of the Gm-C filter can be realized. The above calibration process only requires the pulse generation module 202 and the counter 203 in the calibration circuit 200 to run once or multiple times at startup, and then the count value N is saved for the calibration module 204 to call. Since the transconductance value Gm of the transconductance amplifier 201 is proportional to the count value N, the digital control of the bandwidth of the Gm-C filter can be realized by proportionally enlarging or reducing the count value N.

[0072] The embodiments of the present invention are as described above, and these embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. The scope of protection of the present invention shall be based on the scope defined by the claims of the present invention.

Claims

1. A calibration circuit for a Gm-C filter, for providing a calibrated transconductance control signal to the Gm-C filter, comprising: A pulse generating module, used for generating a pulse signal whose pulse width is proportional to the capacitance value of the reference capacitor; A counter connected to the pulse generating module, using a system clock to count the pulse width of the pulse signal to obtain a count value, where the count value N=T / T0, T is the pulse width of the pulse signal, and T0 is the period of the system clock; a transconductance amplifier for converting an input voltage signal into a first current and a second current which are in opposite phases to each other; as well as a calibration module, connected to the counter and the transconductance amplifier, generating the transconductance control signal according to the first current, the second current and the count value, The control end of the transconductance amplifier receives the transconductance control signal as a feedback signal, and the transconductance amplifier adjusts its own transconductance value according to the transconductance control signal.

2. The calibration circuit according to claim 1, wherein: The calibration module comprises: a first current branch, superimposing the first current with a current signal to obtain a first branch current, wherein the current signal is proportional to the count value; a second current branch, superimposing the second current and a third current to obtain a second branch current, wherein the third current is proportional to the current signal; a third resistor, located on the first current branch to generate a first voltage signal corresponding to the first branch current; a fourth resistor, located on the second current branch to generate a second voltage signal corresponding to the second branch current; A first operational amplifier, wherein the inverting input terminal of the first operational amplifier receives the first voltage signal, the non-inverting input terminal receives the second voltage signal, and the output terminal provides the transconductance control signal.

3. The calibration circuit according to claim 2 further includes a first voltage generating module, which includes a first current source, a first resistor and a second current source connected in series in sequence, the first current source and the second current source provide reference currents equal to each other in the same direction, and the two ends of the first resistor are respectively connected to the non-inverting input terminal and the inverting input terminal of the transconductance amplifier to provide the input voltage signal.

4. The calibration circuit according to claim 3, wherein: The first current branch includes a third current source, the third current source is coupled with the first current source in a current mirror manner to generate the current signal, and the current proportionality coefficient between the current signal and the reference current is adjusted according to the count value.

5. The calibration circuit according to claim 4, wherein: The current proportionality factor is equal to the count value.

6. The calibration circuit according to claim 3, wherein: The second current branch includes a fourth current source, the fourth current source is coupled with the third current source in a current mirror manner to generate the third current, and a current proportionality coefficient between the third current and the current signal is a fixed value.

7. The calibration circuit according to claim 3, wherein: The pulse generating module comprises: a second operational amplifier and a third operational amplifier; A second resistor connected to the inverting input terminal of the second operational amplifier; A first switch and a reference capacitor are connected in parallel between the inverting input terminal and the output terminal of the second operational amplifier; and a second switch connected between the output terminal of the third operational amplifier and ground, The inverting input terminal of the second operational amplifier receives the first reference voltage via the second resistor, the non-inverting input terminal receives the second reference voltage, and the output terminal provides an intermediate signal. The inverting input terminal of the third operational amplifier is connected to the output terminal of the second operational amplifier to receive the intermediate signal, the non-inverting input terminal receives a third reference voltage, and the output terminal provides the pulse signal.

8. The calibration circuit according to claim 7, wherein: The second operational amplifier integrates the current starting from a second reference voltage to generate a triangular wave signal as an intermediate signal, and the first switch and the second switch are in an off state during the integration period.

9. The calibration circuit according to claim 7, wherein: A resistance ratio of the second resistor to the first resistor is a predetermined value.

10. The calibration circuit according to claim 7, further comprising a second voltage generating module, wherein the second voltage generating module comprises a fifth current source, a seventh resistor, a sixth resistor and a fifth resistor connected in series between the power supply terminal and the ground in sequence, in, The first reference voltage is generated across the fifth resistor, the second reference voltage is generated across the fifth resistor and the sixth resistor, and the third reference voltage is generated across the fifth resistor, the sixth resistor, and the seventh resistor.

11. The calibration circuit according to claim 1, wherein: The control end of the transconductance amplifier receives the transconductance control signal for feedback adjustment of the transconductance value of the transconductance amplifier, so that the ratio of the transconductance value of the transconductance amplifier itself to the capacitance value of the reference capacitor is a fixed value.

12. The calibration circuit according to claim 1, wherein: When the calibration circuit is started, the pulse generating module and the counter are enabled to obtain and store the count value, and then the pulse generating module and the counter are disabled.

13. The calibration circuit according to claim 1, wherein: The calibration module receives a digital value after the count value is scaled up or down to achieve digital control of the bandwidth of the Gm-C filter.

14. A calibration method for a Gm-C filter, for providing a calibrated transconductance control signal to the Gm-C filter, comprising: Generate a pulse signal whose pulse width is proportional to the capacitance value of the reference capacitor; The pulse width of the pulse signal is counted using a system clock to obtain a count value, where the count value N=T / T0, T is the pulse width of the pulse signal, and T0 is the period of the system clock; Using a transconductance amplifier to convert an input voltage signal into a first current and a second current that are in opposite phases to each other; generating the transconductance control signal according to the first current, the second current and the count value; as well as The transconductance control signal is provided as a feedback signal to a control terminal of the transconductance amplifier to adjust the transconductance value of the transconductance amplifier.

15. The calibration method according to claim 14, wherein: The step of generating the transconductance control signal comprises: superimposing the first current and a current signal to obtain a first branch current, wherein the current signal is proportional to the count value; superimposing the second current and the third current to obtain a second branch current, wherein the third current is proportional to the current signal; generating a first voltage signal corresponding to the first branch current; generating a second voltage signal corresponding to the second branch current; and The first voltage signal and the second voltage signal are differentially amplified to obtain the transconductance control signal.

16. The calibration method according to claim 15, wherein: The current proportionality coefficient between the current signal and the reference current is adjusted according to the count value.

17. The calibration method according to claim 16, wherein: The current proportionality factor is equal to the count value.

18. The calibration method according to claim 15, wherein: The current proportionality coefficient between the third current and the current signal is a fixed value.

19. The calibration method according to claim 14, wherein: The steps of generating a pulse signal include: integrating the current starting from a second reference voltage to generate a triangular wave signal as an intermediate signal; and The triangular wave signal is compared with a third reference voltage to generate the pulse signal.

20. The calibration method according to claim 19, wherein: Repeat the steps of integrating the current starting from the second reference voltage and comparing the triangular wave signal with the third reference voltage to generate multiple triangular wave signals and multiple pulse signals, and use the system clock to count the pulse widths of the multiple pulse signals respectively and take the average value to obtain the count value.

21. The calibration method according to claim 14, wherein: The control end of the transconductance amplifier receives the transconductance control signal for feedback adjustment of the transconductance value of the transconductance amplifier, so that the ratio of the transconductance value of the transconductance amplifier itself to the capacitance value of the reference capacitor is a fixed value.

22. The calibration method according to claim 14, wherein: The steps of generating a pulse signal and counting the pulse signal are performed when the calibration circuit is started, and then the count value is stored, and the steps of generating a pulse signal and counting the pulse signal are stopped.

23. The calibration method according to claim 14, wherein: The count value is proportionally enlarged or reduced to achieve digital control of the bandwidth of the Gm-C filter.

24. A Gm-C filtering device, comprising: The calibration circuit according to any one of claims 1 to 13; as well as The Gm-C filter is connected to the calibration circuit to receive the calibrated transconductance control signal.

25. The Gm-C filter device according to claim 24, wherein: The Gm-C filter and the calibration circuit are integrated into a single chip.

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