Impedance conversion circuit and oscilloscope front-end circuit

Abstract

An impedance conversion circuit and an oscilloscope front-end circuit, relating to the technical fields of electrical measurement and electronic measurement. The impedance conversion circuit comprises an alternating current coupling module, a voltage and current conversion module, a series current and voltage conversion module, a parallel current and voltage conversion module, an amplifier module, and an integrator module. The voltage and current conversion module acquires a high-frequency voltage signal and a voltage adjustment signal to generate a first current signal; the series current and voltage conversion module is connected to the voltage and current conversion module to transmit the first current signal and convert the first current signal into a first voltage signal; and the parallel current and voltage conversion module is connected to the series current and voltage conversion module so as to generate an output voltage signal and a reference voltage. The integrator module is connected to the amplifier module, the series current and voltage conversion module, and the parallel current and voltage conversion module so as to generate a voltage adjustment signal and input the voltage adjustment signal into the voltage and current conversion module. In this way, provided are an impedance conversion circuit and an oscilloscope front-end circuit each of which the high-frequency output impedance and the low-frequency output impedance are the same.

Description

Impedance conversion circuit and oscilloscope front-end circuit Technical Field

[0001] The present invention relates to the fields of electrical engineering, electronics and measurement technology, and in particular to an impedance conversion circuit of an oscilloscope and a front-end circuit of the oscilloscope. Background Art

[0002] Digital oscilloscopes are common general-purpose test and measurement equipment. In existing technology, digital oscilloscopes typically include input analog front-end circuitry, analog-to-digital conversion circuitry, digital processing circuitry, and display circuitry. The input analog front-end circuitry of an oscilloscope is used to condition the input signal, including input impedance matching, signal attenuation, AC coupling, DC coupling, signal amplification, and DC biasing. Therefore, the input analog front-end circuitry often determines the oscilloscope's key performance indicators.

[0003] The existing oscilloscope analog front-end circuit is shown in Figure 1 and includes an input impedance selector, an attenuation circuit, an impedance conversion circuit, an AD / DC coupling selector, a bias adjustment circuit, and a variable gain amplifier circuit. The impedance conversion circuit utilizes a high-frequency and low-frequency path separation circuit. This circuit requires adjusting the gain of the low-frequency path to align with the gain of the high-frequency path to achieve a flat amplitude-frequency response and avoid the problem of low-frequency square wave distortion caused by an uneven amplitude-frequency response. The low-frequency path of this circuit utilizes voltage-type deep negative feedback, so the output impedance approaches zero at low frequencies. However, the high-frequency path does not utilize deep negative feedback, so the output impedance does not approach zero at high frequencies. For example, the high-frequency output impedance in the oscilloscope analog front-end circuit diagram in Figure 1 is the output impedance of transistor Q24. The output impedance of this circuit at low frequencies is inconsistent with its output impedance at high frequencies. As a result, when the load driven by this circuit changes, the change in the low-frequency gain is inconsistent with the change in the high-frequency gain, resulting in an uneven amplitude-frequency response. Summary of the Invention

[0004] The main technical problem solved by the present invention is to provide an impedance conversion circuit in which the output impedance at low frequency is the same as the output impedance at high frequency.

[0005] According to the first aspect, an embodiment provides an impedance conversion circuit, including:

[0006] an AC coupling module, configured to obtain an input signal and extract a high-frequency voltage signal from the input signal;

[0007] a voltage-current conversion module, wherein a first input terminal of the voltage-current conversion module is connected to the output terminal of the AC coupling module; a second input terminal of the voltage-current conversion module is used to obtain a voltage adjustment signal; the voltage-current conversion module converts the high-frequency voltage signal and the voltage adjustment signal into current signals respectively and sums them to generate a first current signal;

[0008] a series current-voltage conversion module connected to the voltage-current conversion module; a first output end of the series current-voltage conversion module is used to output the first current signal, and a second output end of the series current-voltage conversion module is used to convert the first current signal into a first voltage signal;

[0009] a parallel current-voltage conversion module, connected to the first output terminal of the series current-voltage conversion module; the first output terminal of the parallel current-voltage conversion module is used to convert the first current signal into a second voltage signal to generate an output voltage signal; the second output terminal of the parallel current-voltage conversion module is used to output a reference voltage;

[0010] an amplification module, configured to obtain an input signal and a DC bias signal, and amplify and sum the input signal and the DC bias signal to generate an amplified signal;

[0011] An integrator module, wherein the first input end of the integrator module is connected to the amplification module; the second input end of the integrator module is connected to the second output end of the series current-voltage conversion module; the third input end of the integrator module is connected to the second output end of the parallel current-voltage conversion module; the integrator module obtains the reference voltage to compare and integrate the amplified signal, the first voltage signal and the reference voltage to generate the voltage adjustment signal.

[0012] In one embodiment, the voltage-current conversion module includes a resistor R6, a transistor Q2, a resistor R7 and a filter capacitor C3;

[0013] The first end of the resistor R6 is connected to the output end of the AC coupling module, and the second end of the resistor R6 is used to obtain the operating voltage; the control end of the transistor Q2 is connected to the first end of the resistor R6, the first end of the transistor Q2 is connected to the first end of the resistor R7, the second end of the transistor Q2 is connected to the series current-voltage conversion module, the second end of the resistor R7 is connected to the first end of the filter capacitor C3, the second end of the filter capacitor C3 is grounded, and the second end of the resistor R7 is also used to obtain the voltage adjustment signal.

[0014] In one embodiment, the series current-voltage conversion module includes a current sampling resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13 and an amplifier U3;

[0015] The first end of the current sampling resistor R8 is connected to the voltage-current conversion module, and the second end of the current sampling resistor R8 serves as the first output end of the series current-voltage conversion module; the second end of the current sampling resistor R8 is also connected to the first end of the resistor R9, and the first end of the current sampling resistor R8 is also connected to the first end of the resistor R10, the second end of the resistor R9 is connected to the inverting input end of the amplifier U3, the second end of the resistor R10 is connected to the non-inverting input end of the amplifier U3, the second end of the resistor R9 is also connected to the first end of the resistor R12, the second end of the resistor R12 is connected to the output end of the amplifier U3, the second end of the resistor R10 is also connected to the first end of the resistor R11, and the second end of the resistor R11 is grounded; the output end of the amplifier U3 is also connected to the first end of the resistor R13, and the second end of the resistor R13 serves as the second output end of the series current-voltage conversion module.

[0016] In one embodiment, the parallel current-voltage conversion module includes a resistor R14 and a resistor R15;

[0017] The first end of the resistor R14 is connected to the first output end of the series current-voltage conversion module, and the first end of the resistor R14 also serves as the first output end of the parallel current-voltage conversion module; the second end of the resistor R14 is connected to the first end of the resistor R15, and the first end of the resistor R15 is also connected to the reference voltage, and the second end of the resistor R15 serves as the second output end of the parallel current-voltage conversion module.

[0018] In one embodiment, the amplification module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5 and an amplifier U1;

[0019] The first end of the resistor R1 is used to obtain an input signal, the second end of the resistor R1 is connected to the first end of the resistor R2, the second end of the resistor R2 is grounded, and the first end of the resistor R2 is also connected to the non-inverting input end of the amplifier U1. The first end of the resistor R4 is used to obtain a DC bias signal, the second end of the resistor R4 is connected to the inverting input end of the amplifier U1, the output end of the amplifier U1 is connected to the first end of the resistor R5, and the second end of the resistor R5 is used to output the amplified signal; the first end of the resistor R3 is connected to the second end of the resistor R4, and the second end of the resistor R3 is connected to the first end of the resistor R5.

[0020] In one embodiment, the integrator module includes an amplifier U2, a capacitor C2, and a transistor Q3;

[0021] The non-inverting input terminal of the amplifier U2 is grounded, the inverting input terminal of the amplifier U2 is connected to the amplification module, the inverting input terminal of the amplifier U2 is also connected to the second output terminal of the series current-voltage conversion module, and the inverting input terminal of the amplifier U2 is also connected to the second output terminal of the parallel current-voltage conversion module. The output terminal of the amplifier U2 is connected to the control terminal of the transistor Q3, the first terminal of the transistor Q3 is connected to the working voltage, and the second terminal of the transistor Q3 is used to output the voltage adjustment signal; the first terminal of the capacitor C2 is connected to the output terminal of the amplifier U3, and the second terminal of the capacitor C2 is connected to the inverting input terminal of the amplifier U3.

[0022] In one embodiment, the AC coupling module includes a capacitor C1 , a first end of the capacitor C1 is used to obtain the input signal, and a second end of the capacitor C1 is used to output the high-frequency voltage signal.

[0023] In one embodiment, the impedance conversion circuit determines the low-frequency gain of the impedance conversion circuit according to the series current-voltage conversion module, the parallel current-voltage conversion module, the amplification module and the integrator module; the impedance conversion circuit determines the high-frequency gain of the impedance conversion circuit according to the voltage-current conversion module and the parallel current-voltage conversion module.

[0024] According to a second aspect, an embodiment provides an impedance conversion circuit of an oscilloscope, comprising:

[0025] an AC coupling module, configured to obtain an input signal and extract a high-frequency voltage signal from the input signal;

[0026] a voltage-current conversion module, wherein a first input terminal of the voltage-current conversion module is connected to the output terminal of the AC coupling module for inputting the high-frequency voltage signal; a second input terminal of the voltage-current conversion module is used to obtain a voltage adjustment signal; the voltage-current conversion module generates a first current signal based on the high-frequency voltage signal and the voltage adjustment signal, and the first current signal is output from the output terminal of the voltage-current conversion module;

[0027] a series current-voltage conversion module, connected to the output end of the voltage-current conversion module, configured to input a first current signal and output the first current signal through the first output end of the series current-voltage conversion module; the series current-voltage conversion module is further configured to convert the first current signal into a first voltage signal and output the first voltage signal through the second output end of the series current-voltage conversion module;

[0028] a parallel current-voltage conversion module, connected to the first output terminal of the series current-voltage conversion module, configured to input a first current signal and convert the first current signal into a second voltage signal, the second voltage signal being output through the first output terminal of the parallel current-voltage conversion module and serving as an output voltage signal of the impedance conversion circuit;

[0029] an amplification module, configured to obtain an input signal and amplify the input signal to generate an amplified signal;

[0030] An integrator module, wherein a first input end of the integrator module is connected to the output end of the amplification module, a second input end of the integrator module is connected to the second output end of the series current-voltage conversion module, and the integrator module obtains the amplified signal and the first voltage signal, and compares and integrates the amplified signal and the first voltage signal to generate the voltage adjustment signal.

[0031] According to a third aspect, an embodiment provides an oscilloscope front-end circuit, including:

[0032] A DC bias circuit, used for outputting a DC bias signal;

[0033] An impedance conversion circuit, wherein the impedance conversion circuit adopts the impedance conversion circuit described in any one of the above embodiments;

[0034] The variable gain amplifier is used to amplify or attenuate the voltage of the signal output by the impedance changing circuit.

[0035] According to the above embodiment, an impedance conversion circuit and an oscilloscope front-end circuit are provided. The impedance conversion circuit includes an AC coupling module, a voltage-current conversion module, a series current-voltage conversion module, a parallel current-voltage conversion module, an amplifier module, and an integrator module. The voltage-current conversion module obtains a high-frequency voltage signal and a voltage adjustment signal to generate a first current signal; the series current-voltage conversion module is connected to the voltage-current conversion module to transmit the first current signal and convert the first current signal into a first voltage signal; the parallel current-voltage conversion module is connected to the series current-voltage conversion module to generate an output voltage signal and a reference voltage. The integrator module is connected to the amplifier module, the series current-voltage conversion module, and the parallel current-voltage conversion module to generate a voltage adjustment signal, which is input to the voltage-current conversion module. An integrator module is used to connect the series voltage conversion module so that the series voltage conversion module is a current-type negative feedback. Under this negative feedback, the output impedance of the impedance change circuit in the low frequency band is only determined by the parallel current-voltage conversion module. At the same time, since the integrator module needs to obtain a better integration result, the integrator module operates in the low frequency band and does not operate in the high frequency band. Therefore, the output impedance in the high frequency band is also only determined by the parallel current-voltage conversion module, so that the output impedance at low frequency is the same as the output impedance at high frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a circuit diagram of an existing oscilloscope analog front-end circuit in the background art;

[0037] FIG2 is a schematic structural diagram of an impedance conversion circuit according to an embodiment;

[0038] FIG3 is a circuit diagram of an impedance conversion circuit according to an embodiment;

[0039] FIG4 is a circuit diagram of an oscilloscope analog front-end circuit according to another embodiment. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below by means of specific embodiments in conjunction with the accompanying drawings. Similar elements in different embodiments are numbered with associated similar elements. In the following embodiments, many detailed descriptions are provided to enable the present application to be better understood. However, those skilled in the art will readily appreciate that some of the features may be omitted in different circumstances, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the present application are not shown or described in the specification. This is to avoid the core portion of the present application being overwhelmed by excessive descriptions, and for those skilled in the art, it is not necessary to describe these related operations in detail. They will fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0041] In addition, the features, operations, or characteristics described in the specification may be combined in any appropriate manner to form various embodiments. Furthermore, the steps or actions in the method description may be reordered or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various sequences in the specification and drawings are provided solely for the purpose of clearly describing a particular embodiment and are not intended to be mandatory, unless otherwise specified.

[0042] The serial numbers assigned to components herein, such as "first," "second," etc., are used solely to distinguish the objects being described and do not convey any sequential or technical meaning. References to "connection" and "coupling" herein, unless otherwise specified, include both direct and indirect connections (couplings).

[0043] In order to solve the problem that the output impedance of the impedance conversion circuit in the prior art is inconsistent at low frequency and high frequency, the present application provides an impedance conversion circuit, which is described in detail below.

[0044] In an embodiment of the present application, the oscilloscope includes a data acquisition module, a data processing module, and a waveform generation module. The data acquisition module employs the oscilloscope front-end circuit described in the above embodiment to acquire signal data from each acquisition channel of the oscilloscope. The data processing module is connected to the data acquisition module to process the acquired signal data. The waveform generation module is connected to the data processing module to generate waveform image data based on the processed signal data.

[0045] Referring to Figure 4 , an embodiment of an oscilloscope front-end circuit includes a DC bias circuit 200, an impedance conversion circuit 100, and a variable gain amplifier 300. The DC bias circuit 200 is configured to output a DC bias signal. The impedance conversion circuit 100 employs any of the following embodiments, which are described in detail below. The variable gain amplifier 300 acquires the signal output by the impedance conversion circuit 100 and performs voltage amplification or voltage attenuation on the signal.

[0046] Please refer to Figure 2. In one embodiment, the impedance conversion circuit 100 of the present application includes an AC coupling module 110, a voltage-current conversion module 120, a series current-voltage conversion module 130, a parallel current-voltage conversion module 140, an amplification module 150 and an integrator module 160, which will be expanded one by one below.

[0047] Referring to FIG. 3 , in one embodiment, the AC coupling module 110 includes a capacitor C1. The first end of the capacitor C1 is used to obtain the input signal and block the DC and low-frequency signals in the input signal from entering the voltage-current conversion module, that is, extracting the high-frequency voltage signal from the input signal.

[0048] In one embodiment, the voltage-to-current conversion module 120 includes two input terminals and one output terminal. The first input terminal of the voltage-to-current conversion module 120 is connected to the output terminal of the AC coupling module 110, i.e., the second terminal of the capacitor C1. The second input terminal of the voltage-to-current conversion module 120 is used to obtain a voltage adjustment signal. The voltage-to-current conversion module first converts the high-frequency voltage signal and the voltage adjustment signal into current signals, respectively, and then sums the converted current signals to generate a first current signal. The first current signal is output from the output terminal of the voltage-to-current conversion module 120.

[0049] Please refer to Figure 3. In one embodiment, the voltage-current conversion module 120 includes a resistor R6, a transistor Q2, a resistor R7, and a filter capacitor C3. The first end of the resistor R6 is connected to the second end of the capacitor C1, and the second end of the resistor R6 is used to obtain the operating voltage (i.e., VEE1 in Figure 3, VEE1 provides a static operating voltage to the transistor Q2 through the resistor R6). The control end of the transistor Q2 is connected to the first end of the resistor R6, the first end of the transistor Q2 is connected to the first end of the resistor R7, and the second end of the transistor Q2 serves as the output end of the voltage-current conversion module 120 and is connected to the series current-voltage conversion module 130. The second end of the resistor R7 is connected to the first end of the filter capacitor C3, and the second end of the filter capacitor C3 is grounded. The second end of the resistor R7 is also used to obtain a voltage adjustment signal, wherein the resistor R7 is used to provide the conversion gain of the voltage-current conversion module 120. In the voltage-current conversion module 120, the relationship between the sum of the high-frequency voltage signal and the voltage adjustment signal and the first current signal is: I = V / R R7 Where I is the current corresponding to the first current signal, V is the voltage sum corresponding to the high-frequency voltage signal and the voltage adjustment signal, and R R7 is the resistance value of resistor R7.

[0050] In one embodiment, the series current-voltage conversion module 130 includes one input terminal and two output terminals. The input terminal of the series current-voltage conversion module 130 is connected to the output terminal of the voltage-current conversion module. The first output terminal of the series current-voltage conversion module 130 directly outputs the first current signal output by the voltage-current conversion module, and the second output terminal of the series current-voltage conversion module 130 converts the first current signal into a first voltage signal and then outputs it.

[0051] Referring to Figure 3 , in one embodiment, the series current-voltage conversion module 130 includes a current sampling resistor R8 , a resistor R9 , a resistor R10 , a resistor R11 , a resistor R12 , a resistor R13 , and an amplifier U3 . The first end of the current sampling resistor R8 serves as the input of the series current-voltage conversion module 130 and is connected to the voltage-current conversion module 120 . The second end of the current sampling resistor R8 serves as the first output of the series current-voltage conversion module 130 and directly outputs a first current signal. The second end of the current sampling resistor R8 is also connected to the first end of the resistor R9, the first end of the current sampling resistor R8 is also connected to the first end of the resistor R10, the second end of the resistor R9 is connected to the inverting input terminal of the amplifier U3, the second end of the resistor R10 is connected to the non-inverting input terminal of the amplifier U3, the second end of the resistor R9 is also connected to the first end of the resistor R12, the second end of the resistor R12 is connected to the output terminal of the amplifier U3, the second end of the resistor R10 is also connected to the first end of the resistor R11, the second end of the resistor R11 is grounded, the output terminal of the amplifier U3 is also connected to the first end of the resistor R13, the second end of the resistor R13 serves as the second output terminal of the series current-voltage conversion module, and outputs the first voltage signal.

[0052] It should be noted that in the series current-voltage conversion module 130, the current sampling resistor R8 is used to convert the first current signal into a first voltage signal. The operational amplifier U3 and the peripheral resistors are used to extract the first voltage signal converted by the current sampling resistor R8, amplify it, and output it to the integrator module 160 through the resistor R13. In addition, in one embodiment, the resistance value of the resistor R9 is equal to the resistance value of the resistor R10, and the resistance value of the resistor R12 is equal to the resistance value of the resistor R11.

[0053] In one embodiment, the parallel current-voltage conversion module 140 includes an input terminal and two output terminals. The input terminal of the parallel current-voltage conversion module 140 is connected to the first output terminal of the series current-voltage conversion module, and is used to obtain a first current signal and convert the first current signal into a second voltage signal, thereby generating an output voltage signal, which is output from the first output terminal of the parallel current-voltage conversion module 140. The second output terminal of the parallel current-voltage conversion module 140 is used to output a reference voltage.

[0054] Referring to FIG3 , in one embodiment, the parallel current-voltage conversion module 140 includes a resistor R14 and a resistor R15. The first end of resistor R14 is connected in series with the first output end of the current-voltage conversion module 130. The first end of resistor R14 also serves as the first output end of the parallel current-voltage conversion module 140 to output an output voltage signal. The second end of resistor R14 and the first end of resistor R15 are connected to a reference voltage (i.e., VCC in FIG3 ). The second end of resistor R15 serves as the second output end of the parallel current-voltage conversion module 140 to output the reference voltage to the integrator module 160.

[0055] It should be noted that resistor R14 converts the first current signal into a second voltage signal and determines the output impedance of the output voltage signal. Reference voltage VCC is connected to integrator module 160 through resistor R15, providing voltage to integrator module 160 to provide static operating current for voltage-to-current conversion module 120. The static operating current is calculated using the following formula:

[0056] Among them, VCC represents the reference voltage, R R13 Indicates the resistance value of resistor R13, R R9 Indicates the resistance value of resistor R9, R R15 Indicates the resistance value of resistor R15, R R8 Indicates the resistance value of resistor R8, R R12 Indicates the resistance value of resistor R12.

[0057] In one embodiment, the amplifier module 150 includes two input terminals and one output terminal. The first input terminal of the amplifier module 150 is used to obtain an input signal, and the second input terminal of the amplifier module 150 is used to obtain a DC bias signal. The amplifier module 150 amplifies and sums the input signal and the DC bias signal to generate an amplified signal, which is output through the output terminal of the amplifier module 150. In one embodiment, the amplifier module 150 is a low-frequency amplifier.

[0058] Referring to FIG3 , in one embodiment, the amplification module 150 includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, and an amplifier U1. The first end of the resistor R1 serves as the first input end of the amplification module 150 for obtaining an input signal. The second end of the resistor R1 is connected to the first end of the resistor R2, and the second end of the resistor R2 is grounded. The first end of the resistor R2 is also connected to the non-inverting input end of the amplifier U1. The first end of the resistor R4 serves as the second input end of the amplification module 150 for obtaining a DC bias signal. The second end of the resistor R4 is connected to the inverting input end of the amplifier U1. The output end of the amplifier U1 is connected to the first end of the resistor R5. The second end of the resistor R5 serves as the output end of the amplification module 150 for outputting an amplified signal. The first end of the resistor R3 is connected to the second end of the resistor R4, and the second end of the resistor R3 is connected to the first end of the resistor R5.

[0059] In one embodiment, the integrator module 160 includes three input terminals and one output terminal. The first input terminal of the integrator module 160 is connected to the output terminal of the amplifier module 150 to obtain an amplified signal. The second input terminal of the integrator module 160 is connected to the second output terminal of the series current-voltage conversion module 130 to obtain a first voltage signal. The third input terminal of the integrator module 160 is connected to the third output terminal of the parallel current-voltage conversion module 140 to obtain a reference voltage, which provides a static operating current for the voltage-current conversion module 120. The integrator module 160 compares and integrates the obtained amplified signal, the first voltage signal, and the reference voltage to generate a voltage adjustment signal, which is input to the second input terminal of the voltage-current conversion module 120.

[0060] Referring to Figure 3, integrator module 160 includes amplifier U2, capacitor C2, and transistor Q3. The non-inverting input of amplifier U2 is grounded, while the inverting input of amplifier U2 serves as the first input of integrator module 160 and is connected to amplifier module 150. The inverting input of amplifier U2 also serves as the second input of integrator module 160 and is connected to the second output of series current-voltage conversion module 130. The inverting input of amplifier U2 also serves as the third input of integrator module 160 and is connected to the second output of parallel current-voltage conversion module 140. Reference voltage VCC is output to the inverting input of amplifier U2 via resistor R15. Amplifier U2 controls the quiescent current of transistor Q2, thereby providing a quiescent operating current for transistor Q2. The output of amplifier U2 is connected to the control terminal of transistor Q3. The first terminal of transistor Q3 is connected to the operating voltage, and the second terminal of transistor Q3 serves as the output of integrator module 160, outputting a voltage adjustment signal. The first terminal of capacitor C2 is connected to the output of amplifier U3, while the second terminal of capacitor C2 is connected to the inverting input of amplifier U3.

[0061] In one embodiment, amplifier U2 in integrator module 160 operates in low-frequency mode, and the non-inverting input of amplifier U2 is grounded. The inverting input of amplifier U2 is connected to amplifier module 150, series current-to-voltage conversion module 130, and parallel current-to-voltage conversion module 140. The voltage of the output voltage signal output by parallel current-to-voltage conversion module 140 is the voltage of resistor R14 multiplied by the current flowing through sampling resistor R8. Therefore, the current flowing through sampling resistor R8 is the voltage of the output voltage signal divided by the resistance value of resistor R14. The series current-to-voltage conversion module 130 further amplifies the current flowing through sampling resistor R8 and inputs it to the inverting input of amplifier U2. Therefore, the first voltage signal input by the series current-to-voltage conversion module 130 to the inverting input of amplifier U2 includes the output voltage signal. Simultaneously, the inverting input of amplifier U2 also receives an input signal through amplifier module 150. In the integrator module 160, it is mandatory that the voltages at the non-inverting input and the inverting input of the amplifier U2 are equal. However, in the present application, the non-inverting input of the amplifier U2 is grounded, so it is sufficient that the inverting input of the amplifier U2 is zero. That is, the relationship between the input signal passing through the amplifier module 150 and the output voltage signal passing through the series current-voltage conversion module 130 and the parallel current-voltage conversion module 140 is established at the inverting input of the amplifier U2, and the sum is zero. If the sum is not zero, the voltage adjustment signal output from the output of the amplifier U2 is adjusted to make the non-inverting input and the inverting input of the amplifier U2 equal. Thus, the low-frequency gain of the impedance conversion circuit 100 is determined by the load of the series current-voltage conversion module 130, the parallel current-voltage conversion module 140, the amplifier module 150, the integrator module 160, and the output voltage signal. The low-frequency gain of the impedance conversion circuit 100 is obtained by rectifying the relationship between the input signal and the output voltage signal, as shown in the following formula:

[0062] Wherein, GL represents the low-frequency gain of the impedance conversion circuit 100, R R2 Indicates the resistance value of resistor R2, R R3 Indicates the resistance value of resistor R3, R R4 Indicates the resistance value of resistor R4, R R13 Indicates the resistance value of resistor R13, R R14 Indicates the resistance of resistor R14, RL indicates the resistance of the load of the output voltage signal, R R9 Indicates the resistance value of resistor R9, R R1 Indicates the resistance value of resistor R1, R R5 Indicates the resistance value of resistor R5, R R8 Indicates the resistance value of resistor R8, R R12 Indicates the resistance value of resistor R12.

[0063] It should be noted that, in the low-frequency band, a series current-voltage converter is used to provide current-type deep negative feedback, so that the output impedance of the impedance conversion circuit 100 in the low-frequency band is determined solely by the parallel current-voltage converter. That is, because amplifier U2 constantly adjusts the non-inverting input and the inverting input of amplifier U2 to be equal, the current flowing through the current sampling resistor R8 in the series current-voltage conversion module 130 is always constant. Therefore, from the direction of the output voltage signal toward the series current-voltage conversion module 130, the series current-voltage conversion module 130 and the integrator module 160 involving the current sampling resistor R8 are equivalent to a constant current source, whose impedance is infinite. Therefore, in the low-frequency band, the output impedance corresponding to the output voltage signal is equal to the resistor R14 in the parallel current-voltage converter 140 connected in parallel with an infinite resistance, ultimately making the output impedance in the low-frequency band equal to the resistance value of resistor R14. In one embodiment, the resistance value of resistor R14 is designed to be 50Ω.

[0064] In one embodiment, when the impedance conversion circuit 100 operates in the high-frequency mode, the amplifier U2 in the integrator module 160 does not operate. In this case, the high-frequency gain is determined solely by the voltage-to-current conversion module 120, the parallel current-to-voltage conversion module 140, and the load of the output voltage signal. Specifically, the high-frequency gain is determined by the resistor R7, the resistor R14, and the load of the output voltage signal:

[0065] Wherein, GH represents the low-frequency gain of the impedance conversion circuit 100, R R14 Indicates the resistance of resistor R14, RL indicates the resistance of the load of the output voltage signal, R R7 Indicates the resistance value of resistor R7.

[0066] It should be noted that in the high-frequency band, due to the failure of the integrator module 160, the impedance seen from the output voltage signal toward the series current-voltage conversion module 130 is the impedance of the current sampling resistor R8 plus the impedance seen through the collector of transistor Q2. Since transistor Q2 operates in the linear region, the impedance seen through the collector of transistor Q2 is much greater than 50Ω. At this time, the output impedance corresponding to the output voltage signal is the resistor R14 in the parallel current-voltage converter 140 connected in parallel with a resistor much greater than 50Ω (i.e., equivalent to an infinite resistance), ultimately making the output impedance in the high-frequency band equal to the resistance value of resistor R14. In one embodiment, the resistance value of resistor R14 is designed to be 50Ω. In addition, when designing the parameters of the various hardware in the impedance conversion circuit 100, GL=GH.

[0067] In this way, the impedance of the signal output of the impedance conversion circuit 100 provided in the present application in the low frequency band is consistent with the impedance of the signal output in the high frequency band. When the load driven by the circuit changes, the change in the low-frequency gain is consistent with the change in the high-frequency gain, and the frequency response flatness no longer changes with the change in the load driven by the circuit.

[0068] In the embodiments shown in FIG2 and FIG3 , the parallel current-to-voltage conversion module 140 may not provide a reference voltage to the integrator module 160. The integrator module 160 only performs comparison and integration based on the amplified signal output by the amplification module 150 and the first voltage signal output by the series current-to-voltage conversion module 130 to generate a voltage adjustment signal. The voltage-to-current conversion module 120 generates a first current signal based on the voltage modulation signal, and the series current-to-voltage conversion module 130 converts the first current signal into an amplified first voltage signal, thereby forming a closed-loop feedback loop.

[0069] In some embodiments, resistor R6 and filter capacitor C3 in the voltage-to-current conversion module 120 shown in FIG3 are not required. The voltage-to-current conversion module 120 may include only transistor Q2 and resistor R7. The control terminal of transistor Q2 is connected to the output terminal of the AC coupling module, the first terminal of transistor Q2 is connected to the first terminal of resistor R7, the second terminal of transistor Q2, as the output terminal of the voltage-to-current conversion module, is connected to the input terminal of the series current-to-voltage conversion module, and the second terminal of resistor R7 is connected to the output terminal of the integrator module for obtaining the voltage adjustment signal. Resistor R6 provides a reference voltage to stabilize the static operating point of transistor Q2, and filter capacitor C3 filters out high-frequency noise signals output by the integrator module.

[0070] The above examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. Those skilled in the art can make several simple deductions, modifications or substitutions based on the concept of the present invention.

Claims

1. An impedance conversion circuit for an oscilloscope, characterized in that: include: an AC coupling module, configured to obtain an input signal and extract a high-frequency voltage signal from the input signal; a voltage-to-current conversion module, wherein a first input terminal of the voltage-to-current conversion module is connected to the output terminal of the AC coupling module for inputting the high-frequency voltage signal; a second input terminal of the voltage-to-current conversion module is used to obtain a voltage adjustment signal; the voltage-to-current conversion module converts the high-frequency voltage signal and the voltage adjustment signal into current signals respectively and sums them to generate a first current signal, which is output from the output terminal of the voltage-to-current conversion module; a series current-voltage conversion module, connected to the output end of the voltage-current conversion module, configured to input a first current signal and output the first current signal through the first output end of the series current-voltage conversion module; the series current-voltage conversion module is further configured to convert the first current signal into a first voltage signal and output the first voltage signal through the second output end of the series current-voltage conversion module; a parallel current-voltage conversion module connected to the first output terminal of the series current-voltage conversion module; the parallel current-voltage conversion module is used to convert the first current signal into a second voltage signal, the second voltage signal is output through the first output terminal of the parallel current-voltage conversion module and serves as the output voltage signal of the impedance conversion circuit; the second output terminal of the parallel current-voltage conversion module is used to output a reference voltage; an amplification module, configured to obtain an input signal and a DC bias signal, and amplify and sum the input signal and the DC bias signal to generate an amplified signal; An integrator module, wherein the first input end of the integrator module is connected to the output end of the amplification module; the second input end of the integrator module is connected to the second output end of the series current-voltage conversion module; the third input end of the integrator module is connected to the second output end of the parallel current-voltage conversion module; the integrator module obtains the reference voltage to compare and integrate the amplified signal, the first voltage signal and the reference voltage to generate the voltage adjustment signal.

2. The impedance conversion circuit according to claim 1, wherein: The voltage-current conversion module includes a transistor Q2 and a resistor R7; The control end of the transistor Q2 is connected to the output end of the AC coupling module, the first end of the transistor Q2 is connected to the first end of the resistor R7, the second end of the transistor Q2 serves as the output end of the voltage-current conversion module and is connected to the input end of the series current-voltage conversion module, and the second end of the resistor R7 is connected to the output end of the integrator module for obtaining the voltage adjustment signal.

3. The impedance conversion circuit according to claim 2, wherein: The voltage-current conversion module further includes a resistor R6 and a filter capacitor C3; the first end of the resistor R6 is connected to the control end of the transistor Q2, and the second end thereof is used to obtain the operating voltage; the filter capacitor C3 is connected between the second end of the resistor R7 and the ground.

4. The impedance conversion circuit according to claim 1, wherein: The series current-voltage conversion module includes a current sampling resistor R8, a resistor R9, a resistor R10, a resistor R13 and an amplifier U3; The first end of the current sampling resistor R8 is connected to the output end of the voltage-current conversion module, and the second end of the current sampling resistor R8 serves as the first output end of the series current-voltage conversion module; the second end of the current sampling resistor R8 is also connected to the first end of the resistor R9, and the first end of the current sampling resistor R8 is also connected to the first end of the resistor R10, the second end of the resistor R9 is connected to the inverting input end of the amplifier U3, the second end of the resistor R10 is connected to the non-inverting input end of the amplifier U3, the output end of the amplifier U3 is also connected to the first end of the resistor R13, and the second end of the resistor R13 serves as the second output end of the series current-voltage conversion module.

5. The impedance conversion circuit according to claim 4, wherein: The series current-voltage conversion module further includes a resistor R11 and a resistor R12. The resistor R11 is connected between the non-inverting input terminal of the amplifier U3 and the ground, and the resistor R12 is connected between the output terminal and the inverting input terminal of the amplifier U3.

6. The impedance conversion circuit according to claim 1, wherein: The parallel current-voltage conversion module includes a resistor R14; The first end of the resistor R14 is connected to the first output end of the series current-voltage conversion module, and the first end of the resistor R14 also serves as the first output end of the parallel current-voltage conversion module; the second end of the resistor R14 is connected to the voltage VCC.

7. The impedance conversion circuit according to claim 6, wherein: The parallel current-voltage conversion module includes a resistor R15 , a first end of the resistor R15 is connected to the voltage VCC, and a second end of the resistor R15 serves as a second output end of the parallel current-voltage conversion module to provide the reference voltage for the integrator module.

8. The impedance conversion circuit according to claim 1, wherein: The amplification module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5 and an amplifier U1; The first end of the resistor R1 is used to obtain an input signal, the second end of the resistor R1 is connected to the first end of the resistor R2, the second end of the resistor R2 is grounded, and the first end of the resistor R2 is also connected to the non-inverting input end of the amplifier U1. The first end of the resistor R4 is used to obtain a DC bias signal, the second end of the resistor R4 is connected to the inverting input end of the amplifier U1, the output end of the amplifier U1 is connected to the first end of the resistor R5, and the second end of the resistor R5 is used to output the amplified signal; the first end of the resistor R3 is connected to the second end of the resistor R4, and the second end of the resistor R3 is connected to the first end of the resistor R5.

9. The impedance conversion circuit according to claim 1, wherein: The integrator module includes an amplifier U2, a capacitor C2 and a transistor Q3; The non-inverting input terminal of the amplifier U2 is grounded, the inverting input terminal of the amplifier U2 is connected to the amplification module, the inverting input terminal of the amplifier U2 is also connected to the second output terminal of the series current-voltage conversion module, and the inverting input terminal of the amplifier U2 is also connected to the second output terminal of the parallel current-voltage conversion module. The output terminal of the amplifier U2 is connected to the control terminal of the transistor Q3, the first terminal of the transistor Q3 is connected to the working voltage, and the second terminal of the transistor Q3 is used to output the voltage adjustment signal; the first terminal of the capacitor C2 is connected to the output terminal of the amplifier U3, and the second terminal of the capacitor C2 is connected to the inverting input terminal of the amplifier U3.

10. The impedance conversion circuit according to claim 1, wherein: The AC coupling module includes a capacitor C1 , a first end of the capacitor C1 is used to obtain the input signal, and a second end of the capacitor C1 is used to output the high-frequency voltage signal.

11. The impedance conversion circuit according to claim 1, wherein: The impedance conversion circuit determines its low-frequency gain based on the series current-voltage conversion module, the parallel current-voltage conversion module, the amplifier module, and the integrator module; and determines its high-frequency gain based on the voltage-current conversion module and the parallel current-voltage conversion module. This is a limitation of effectiveness, preferably defined by technical means.

12. An impedance conversion circuit for an oscilloscope, characterized in that: include: an AC coupling module, configured to obtain an input signal and extract a high-frequency voltage signal from the input signal; a voltage-current conversion module, wherein a first input terminal of the voltage-current conversion module is connected to the output terminal of the AC coupling module for inputting the high-frequency voltage signal; a second input terminal of the voltage-current conversion module is used to obtain a voltage adjustment signal; the voltage-current conversion module generates a first current signal based on the high-frequency voltage signal and the voltage adjustment signal, and the first current signal is output from the output terminal of the voltage-current conversion module; a series current-voltage conversion module, connected to the output end of the voltage-current conversion module, configured to input a first current signal and output the first current signal through the first output end of the series current-voltage conversion module; the series current-voltage conversion module is further configured to convert the first current signal into a first voltage signal and output the first voltage signal through the second output end of the series current-voltage conversion module; a parallel current-voltage conversion module, connected to the first output terminal of the series current-voltage conversion module, configured to input a first current signal and convert the first current signal into a second voltage signal, the second voltage signal being output through the first output terminal of the parallel current-voltage conversion module and serving as an output voltage signal of the impedance conversion circuit; an amplification module, configured to obtain an input signal and amplify the input signal to generate an amplified signal; An integrator module, wherein a first input end of the integrator module is connected to the output end of the amplification module, a second input end of the integrator module is connected to the second output end of the series current-voltage conversion module, and the integrator module obtains the amplified signal and the first voltage signal, and compares and integrates the amplified signal and the first voltage signal to generate the voltage adjustment signal.

13. The impedance conversion circuit according to claim 12, wherein: The voltage-current conversion module includes a transistor Q2 and a resistor R7; the control end of the transistor Q2 is connected to the output end of the AC coupling module, the first end of the transistor Q2 is connected to the first end of the resistor R7, the second end of the transistor Q2 serves as the output end of the voltage-current conversion module and is connected to the input end of the series current-voltage conversion module, and the second end of the resistor R7 is connected to the output end of the integrator module for obtaining the voltage adjustment signal.

14. The impedance conversion circuit according to claim 13, wherein: The voltage-current conversion module further includes a resistor R6 and a filter capacitor C3; the first end of the resistor R6 is connected to the control end of the transistor Q2, and the second end thereof is used to obtain the operating voltage; the filter capacitor C3 is connected between the second end of the resistor R7 and the ground.

15. The impedance conversion circuit according to claim 12, wherein: The series current-voltage conversion module includes a flow sampling resistor R8, a resistor R9, a resistor R10, a resistor R13 and an amplifier U3; the first end of the flow sampling resistor R8 is connected to the output end of the voltage-current conversion module, and the second end of the flow sampling resistor R8 serves as the first output end of the series current-voltage conversion module; the second end of the flow sampling resistor R8 is also connected to the first end of the resistor R9, the first end of the flow sampling resistor R8 is also connected to the first end of the resistor R10, the second end of the resistor R9 is connected to the inverting input end of the amplifier U3, the second end of the resistor R10 is connected to the non-inverting input end of the amplifier U3, the output end of the amplifier U3 is also connected to the first end of the resistor R13, and the second end of the resistor R13 serves as the second output end of the series current-voltage conversion module.

16. The impedance conversion circuit according to claim 15, wherein: The series current-voltage conversion module further includes a resistor R11 and a resistor R12. The resistor R11 is connected between the non-inverting input terminal of the amplifier U3 and the ground, and the resistor R12 is connected between the output terminal and the inverting input terminal of the amplifier U3.

17. The impedance conversion circuit according to claim 12, wherein: The parallel current-voltage conversion module includes a resistor R14; the first end of the resistor R14 is connected to the first output end of the series current-voltage conversion module, and the first end of the resistor R14 also serves as the first output end of the parallel current-voltage conversion module; the second end of the resistor R14 is connected to the voltage VCC.

18. The impedance conversion circuit according to claim 17, wherein: The parallel current-voltage conversion module includes a resistor R15, a first end of the resistor R15 is connected to a reference voltage VCC, and a second end of the resistor R15 is connected to a second input end of the integrator module. The integrator module obtains a voltage provided by the reference voltage through the resistor R15 to compare and integrate the amplified signal, the first voltage signal, and the voltage provided by the reference voltage through the resistor R15 to generate the voltage adjustment signal.

19. The impedance conversion circuit according to claim 12, wherein: The integrator module includes an amplifier U2, a capacitor C2 and a transistor Q3; the non-inverting input of the amplifier U2 is grounded, the inverting input of the amplifier U2 is connected to the amplification module, the inverting input of the amplifier U2 is also connected to the second output of the series current-voltage conversion module, the inverting input of the amplifier U2 is also connected to the second output of the parallel current-voltage conversion module, the output of the amplifier U2 is connected to the control end of the transistor Q3, the first end of the transistor Q3 is connected to the working voltage, and the second end of the transistor Q3 is used to output the voltage adjustment signal; the first end of the capacitor C2 is connected to the output of the amplifier U3, and the second end of the capacitor C2 is connected to the inverting input of the amplifier U3.

20. An oscilloscope front-end circuit, characterized in that: include: A DC bias circuit, used for outputting a DC bias signal; An impedance conversion circuit, wherein the impedance conversion circuit adopts the impedance conversion circuit according to any one of claims 1 to 19; A variable gain amplifier is used to amplify or attenuate the voltage of the signal output by the impedance conversion circuit.

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