CN212255421U

CN212255421U - Probe circuit of oscilloscope

Info

Publication number: CN212255421U
Application number: CN202020792075.9U
Authority: CN
Inventors: 林辉浪; 邝被华; 宋民
Original assignee: Shenzhen Siglent Technologies Co Ltd
Current assignee: Shenzhen Siglent Technologies Co Ltd
Priority date: 2020-05-13
Filing date: 2020-05-13
Publication date: 2020-12-29
Anticipated expiration: 2030-05-13

Abstract

A probe circuit of an oscilloscope comprises a BNC interface, wherein the probe circuit comprises a high-low pass attenuation circuit, an impedance transformation circuit, a bias feedback circuit and a source end matching circuit; the high-low pass attenuation circuit is used for performing high-low pass attenuation processing on a signal to be detected received by a first input end of the high-low pass attenuation circuit to obtain an attenuation signal and outputting the attenuation signal through an output end of the high-low pass attenuation circuit, the impedance transformation circuit is used for performing impedance transformation on the attenuation signal received by the input end of the impedance transformation circuit to obtain a transformation signal and outputting the transformation signal through an output end of the impedance transformation circuit, the bias feedback circuit is used for obtaining a feedback signal according to a bias configuration signal and the transformation signal and outputting the feedback signal through an output end of the bias feedback circuit, and the source end matching circuit is used for performing impedance transformation on the transformation signal to. Due to the action of the bias feedback circuit, the probe circuit has the function of direct current bias adjustment, and the direct current bias adjustment limitation in the prior art is solved.

Description

Probe circuit of oscilloscope

Technical Field

The invention relates to the technical field of oscilloscopes, in particular to a probe circuit of an oscilloscope.

Background

An oscilloscope probe is a device for connecting a signal to be measured to an input of an oscilloscope, the performance of the oscilloscope probe is crucial to the accuracy and correctness of a measurement result, and the oscilloscope probe is essentially an electronic component for connecting the circuit to be measured and the input end of the oscilloscope. The simplest probe is a conducting wire which is used for connecting a tested circuit and the input end of the electronic oscilloscope, and because no shielding measure is adopted, the probe is easily interfered by an external electromagnetic field, and the equivalent capacitance of the probe is large, the load of the tested circuit is easily increased; however, complex probes consist of a resistive-capacitive element and an active device. Oscilloscope probes can be generally classified into active probes and passive probes.

The passive probe is composed of a cable and a passive device, and does not need a power supply. The passive probe can usually provide high input impedance of 1M omega or 10M omega, but the input capacitance cannot be very small, so the bandwidth of the passive probe cannot be very high, and the bandwidth is generally within 500 MHz. The active probe contains source devices such as amplifiers and transistors, and needs an external power supply. The active probe can realize high input impedance and small input capacitance, the load effect is obviously better than that of a passive probe, and the bandwidth of the active probe can be generally more than 1 Ghz.

In addition, the active probe is classified into a single-ended active probe and a differential active probe. The single-ended active probe takes the ground as a reference to realize single-point test of a tested circuit, and can meet most application occasions; the differential probe is mainly used for observing differential signals, and the differential signals are mutually referenced instead of being referenced to the ground. Currently, an active probe is mostly applied to a middle-high-end oscilloscope and is always monopolized by foreign brands such as Taike, Agilent and the like, and the application situations of complex probe structure, high price and high maintenance cost exist.

In the patent document (CN102735887B), an input signal is first input to an impedance transformation module through a high-pass module and a low-pass module to perform impedance transformation and enhancement driving, and then frequency compensation, gain adjustment and output impedance adjustment are performed in an output circuit, and finally output to a rear-stage oscilloscope. Therefore, in the scheme, a signal is input to the impedance transformation network through the high-pass module, and in order to ensure the high input impedance characteristic of the probe, the input end of the impedance transformation network must be a field effect transistor device, for example, a double-gate field effect transistor is used in the existing scheme, the field effect transistor device can limit the bandwidth of the whole probe, so that the bandwidth can only reach 1.5 GHz. In addition, the circuit structure of the scheme has some unreasonables, so that the input signal range is limited by the impedance transformation network, for example, the amplitude of the maximum input signal cannot exceed 2V; the input capacitance of the circuit structure is limited by the field effect transistor device and the parasitic capacitance of the device on the PCB, and smaller input capacitance cannot be achieved; in addition, the output circuit is used for being matched with the input resistor of the oscilloscope to realize 10 times of attenuation (attenuation is 20dB), the circuit structure can not keep the impedance of the output end consistent with the impedance of the cable and the input impedance of the oscilloscope, and obvious signal reflection phenomenon can be generated, so that the bandwidth of the active probe and the flatness in the bandwidth are influenced; in addition, the existing active probe circuit does not have the function of adjusting the direct current bias of the probe, so that the application range of the probe is greatly limited.

Disclosure of Invention

The invention mainly solves the technical problem of how to simplify the structure of the existing single-ended active probe and provides a probe circuit with simple structure, low cost and adjustable direct current bias. In order to solve the technical problem, the application provides a probe circuit of an oscilloscope.

In one embodiment, a probe circuit of an oscilloscope is provided, the oscilloscope includes a BNC interface, and the probe circuit includes a high-low pass attenuation circuit, an impedance transformation circuit, a bias feedback circuit, and a source end matching circuit; the high-low pass attenuation circuit comprises a first input end, a second input end and an output end, wherein the first input end of the high-low pass attenuation circuit is used for being connected with an external circuit to be detected and receiving a signal to be detected transmitted by the circuit to be detected; the high-low pass attenuation circuit is used for carrying out high-low pass attenuation processing on the signal to be detected received by the first input end of the high-low pass attenuation circuit to obtain an attenuation signal, and outputting the attenuation signal through the output end of the high-low pass attenuation circuit; the impedance conversion circuit comprises an input end and an output end, wherein the input end of the impedance conversion circuit is connected with the output end of the high-low pass attenuation circuit and is used for receiving the attenuation signal; the impedance transformation circuit is used for carrying out impedance transformation on the attenuation signal received by the input end of the impedance transformation circuit to obtain a transformation signal and outputting the transformation signal through the output end of the impedance transformation circuit; the bias feedback circuit comprises an input end, an output end and a configuration end, wherein the input end of the bias feedback circuit is connected with the output end of the impedance transformation circuit and used for receiving the transformation signal, the output end of the bias feedback circuit is connected with the second input end of the high-low pass attenuation circuit, and the configuration end of the bias feedback circuit is used for receiving a bias configuration signal; the bias feedback circuit is used for obtaining a feedback signal according to the bias configuration signal and the conversion signal and outputting the feedback signal through an output end of the bias feedback circuit; the source end matching circuit comprises an input end and an output end, and the input end of the source end matching circuit is connected with the output end of the impedance transformation circuit and used for receiving the transformation signal; the output end of the source end matching circuit is used for being connected with a BNC interface of the oscilloscope; the source end matching circuit is used for performing impedance transformation on the transformed signal to obtain a coaxial signal, so that the coaxial signal has output impedance matched with the characteristic impedance of a coaxial cable and the input impedance of a BNC interface; and the output end of the source end matching circuit is used for outputting the coaxial signal.

The high-low pass attenuation circuit comprises a high-pass attenuation circuit and a low-pass attenuation circuit; the high-pass attenuation circuit has an input end and an output end; the low-pass attenuation circuit is provided with an input end, a comparison end and an output end; the input end of the high-pass attenuation circuit and the input end of the low-pass attenuation circuit form a first input end of the high-low-pass attenuation circuit, the output end of the high-pass attenuation circuit and the output end of the low-pass attenuation circuit form an output end of the high-low-pass attenuation circuit, and the comparison end of the low-pass attenuation circuit is used as a second input end of the high-low-pass attenuation circuit; the high-pass attenuation circuit is used for carrying out high-pass attenuation processing on the signal to be detected received by the input end of the high-pass attenuation circuit to obtain a first attenuation signal and outputting the first attenuation signal through the output end of the high-pass attenuation circuit; the low-pass attenuation circuit is used for performing low-pass attenuation processing on the signal to be detected received by the input end of the low-pass attenuation circuit to obtain a second attenuation signal and outputting the second attenuation signal through the output end of the low-pass attenuation circuit; wherein the second attenuated signal and the first attenuated signal constitute the attenuated signal.

The probe circuit of the oscilloscope further comprises a power supply circuit, and the power supply circuit is used for supplying direct current to the high-low pass attenuation circuit and the impedance transformation circuit.

The high-pass attenuation circuit comprises a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4 and a diode D1; one end of the resistor R5 is used as the input end of the high-pass attenuation circuit, the other end of the resistor R5 is connected with one end of the capacitor C2, the other end of the capacitor C2 is used as the output end of the high-pass attenuation circuit, and the capacitor C1 and the resistor R4 are connected in series and then are connected in parallel with a circuit where the resistor R5 and the capacitor C2 are located; the end, which is not connected with the resistor R5, of the capacitor C2 is connected with one end of the capacitor C3, the other end of the capacitor C3 is connected with one end of the resistor R7, the other end of the resistor R7 is connected with the cathode of the diode D1, the anode of the diode D2 is connected with a line where the grounding electricity of the power supply circuit is located, the end, which is connected with the diode D1, of the resistor R7 is connected with the line where the grounding electricity of the power supply circuit is located through the resistor R8 and the resistor R9, and the end, which is opposite to the line where the grounding electricity is located, of the resistor R9 is connected with the line where the anode direct current of the power supply; the end of the capacitor C2, which is not connected with the resistor R5, is also connected with a line where the grounding of the power supply circuit is located through the resistor R6 and the capacitor C4.

The resistor R6 and the resistor R9 are both variable resistors; the two unchangeable ends of the resistor R9 are respectively connected with the circuits where the positive direct current and the grounding current of the power supply circuit are located, and the variable end of the resistor R9 is connected to the end where the resistor R7 and the diode D1 are connected through the resistor R8.

The low-pass attenuation circuit comprises a resistor R2, a resistor R3, a resistor R10 and an amplifier U1; one end of the resistor R2 is used as the input end of the low-pass attenuation circuit, the other end of the resistor R2 is respectively connected with the negative input end of the amplifier U1 and one end of the resistor R3, and the other end of the resistor R3 is connected to a circuit where the grounding electricity of the power supply circuit is located; the positive input end of the amplifier U1 is used as the second input end of the high-low pass attenuation circuit, the output end of the amplifier U1 is connected with one end of a resistor R10, and the other end of the resistor R10 is used as the output end of the low-pass attenuation circuit; the input end of the low-pass attenuation circuit is connected with the input end of the high-pass attenuation circuit and then is connected with one end of a resistor R1, and the other end of the resistor R1 is used for being connected with an external circuit to be detected.

The impedance transformation circuit comprises a triode Q1, a triode Q2, a triode Q3, a resistor R11, a resistor R12, a resistor R13, a resistor R14 and a resistor R15; the control end of the triode Q1 is used as the input end of the impedance transformation circuit, the first end of the triode Q1 is connected with the control end of the triode Q2 through a resistor R11, the first end of the triode Q2 is connected with the control end of the triode Q3 through a resistor R12, and the first end of the triode Q3 is used as the output end of the impedance transformation circuit; second ends of the triode Q1, the triode Q2 and the triode Q3 are all connected with a circuit where positive direct current of the power supply circuit is located, and second ends of the triode Q1, the triode Q2 and the triode Q3 are respectively connected with a circuit where negative direct current of the power supply circuit is located through a resistor R13, a resistor R14 and a resistor R15.

The bias feedback circuit comprises a resistor R16, a resistor R17, a resistor R18 and a resistor R19; one end of the resistor R16 is used as the input end of the bias feedback circuit, and the other end is used as the output end of the bias feedback circuit; the end of the resistor R16, which is used as the output end of the bias feedback circuit, is connected with one end of the resistor R17, the other end of the resistor R17 is respectively connected with one end of the resistor R19 and one end of the resistor R18, the other end of the resistor R19 is used as the configuration end of the bias feedback circuit, and the other end of the resistor R18 is connected with a line where the grounding electricity of the power supply circuit is located; the resistor R17 is a variable resistor.

The source end matching circuit comprises a resistor R20, a resistor R21 and a capacitor C5; two ends of the resistor R20 are respectively used as an input end and an output end of the source end matching circuit, and the resistor R21 and the capacitor C5 are connected in series and then connected in parallel with the resistor R20.

The output end of the source end matching circuit forms a first probe interface, and the first probe interface is used for being matched with a BNC interface of an oscilloscope and outputting the coaxial signal to the BNC interface of the oscilloscope; the configuration end of the bias feedback circuit and a circuit where a positive direct current, a negative direct current and a grounding current of the power supply circuit are located are combined to form a second probe interface, and the second probe interface is used for being matched with a communication interface of the oscilloscope and receiving direct current and bias configuration signals output by the communication interface of the oscilloscope.

The beneficial effect of this application is:

according to the probe circuit of the oscilloscope, the oscilloscope comprises a BNC interface, and the probe circuit comprises a high-low pass attenuation circuit, an impedance conversion circuit, a bias feedback circuit and a source end matching circuit; the high-low pass attenuation circuit is used for performing high-low pass attenuation processing on a signal to be detected received by the first input end of the high-low pass attenuation circuit to obtain an attenuation signal and outputting the attenuation signal through the output end of the attenuation signal, the impedance conversion circuit is used for performing impedance conversion on the attenuation signal received by the input end of the impedance conversion circuit to obtain a conversion signal and outputting the conversion signal through the output end of the impedance conversion circuit, the bias feedback circuit is used for obtaining a feedback signal according to a bias configuration signal and the conversion signal and outputting the feedback signal through the output end of the bias feedback circuit, and the source end matching circuit is used for performing impedance conversion on the conversion signal to obtain a coaxial signal so that the coaxial signal has output. On the first hand, the signal to be detected is transmitted to the impedance transformation network after being subjected to amplitude attenuation through the high-low pass attenuation circuit, so that the signal to be detected can be received by the high-low pass attenuation circuit even if the signal to be detected has a larger input signal range, and the detection of the signal with the larger input signal range is facilitated; in the second aspect, because the triode is used in the impedance conversion circuit to replace the traditional field effect transistor, the impedance conversion circuit has smaller input capacitance and plays a role in reducing the input capacitance of the active probe; in the third aspect, the high-pass attenuation circuit isolates the circuit to be detected and the impedance conversion circuit, and the circuit structure avoids the impedance conversion circuit from being directly exposed at the input side of the signal to be detected, so that the input capacitance of the probe can be greatly reduced, and the probe has higher bandwidth; in the fourth aspect, the bias feedback circuit is provided with a configuration end, so that the bias feedback circuit can receive a bias configuration signal from the controller, and then processes the conversion signal under the action of the bias configuration signal to obtain a feedback signal, and simultaneously, the purpose of freely adjusting the direct current bias is realized, and the problem that the direct current bias of the conventional oscilloscope probe is not adjustable is solved; in the fifth aspect, because the source end matching circuit is arranged at the rear end of the impedance transformation circuit, the problem of reflection of signals in the coaxial transmission process can be reduced by means of the source end matching circuit, the signal amplitude and the flatness are better, and the signal bandwidth required by coaxial signal transmission can be ensured; in a sixth aspect, the probe circuit comprises a high-pass attenuation circuit, a low-pass attenuation circuit, an impedance conversion circuit, a bias feedback circuit and a source end matching circuit, so that when the probe circuit processes a signal to be detected, the probe circuit has excellent performances of higher bandwidth, larger input signal range and smaller input capacitance, and further the performance of the active probe is greatly improved; in a seventh aspect, the probe circuit claimed in the present application may be used in cooperation with an oscilloscope, the probe circuit may be used to effectively process a signal to be detected and make the generated coaxial signal have an output impedance matched with the characteristic impedance of the coaxial cable and the input impedance of the BNC interface, the oscilloscope may be used to not only receive and digitally analyze the coaxial signal, but also effectively control the bias feedback process inside the probe circuit, thereby enhancing the detection performance of the signal detection system on the signal to be detected under the cooperation of the probe circuit and the oscilloscope.

Drawings

FIG. 1 is a schematic diagram showing an overall configuration of a probe circuit of an oscilloscope in one embodiment;

FIG. 2 is a schematic diagram showing the overall structure of a probe circuit of an oscilloscope in another embodiment;

FIG. 3 is a detailed circuit diagram of a probe circuit of an oscilloscope in one embodiment;

FIG. 4 is a detailed circuit diagram of a probe circuit of an oscilloscope in another embodiment;

FIG. 5 is a schematic structural diagram of a first probe interface;

fig. 6 is a schematic structural diagram of a second probe interface.

Detailed Description

The present invention will be described in further detail with reference to the following detailed description and accompanying drawings. Wherein like elements in different embodiments are numbered with like associated elements. In the following description, numerous details are set forth in order to provide a better understanding of the present application. However, those skilled in the art will readily recognize that some of the features may be omitted or replaced with other elements, materials, methods in different instances. In some instances, certain operations related to the present application have not been shown or described in detail in order to avoid obscuring the core of the present application from excessive description, and it is not necessary for those skilled in the art to describe these operations in detail, so that they may be fully understood from the description in the specification and the general knowledge in the art.

Furthermore, the features, operations, or characteristics described in the specification may be combined in any suitable manner to form various embodiments. Also, the various steps or actions in the method descriptions may be transposed or transposed in order, as will be apparent to one of ordinary skill in the art. Thus, the various sequences in the specification and drawings are for the purpose of describing certain embodiments only and are not intended to imply a required sequence unless otherwise indicated where such sequence must be followed.

The numbering of the components as such, e.g., "first", "second", etc., is used herein only to distinguish the objects as described, and does not have any sequential or technical meaning. The term "connected" and "coupled" when used in this application, unless otherwise indicated, includes both direct and indirect connections (couplings).

The first embodiment,

Referring to fig. 1 and 3, the present application provides a probe circuit of an oscilloscope, the probe circuit 1 includes a high-low pass attenuation circuit 11, an impedance transformation circuit 12, a bias feedback circuit 13 and a source end matching circuit 14, and furthermore, the oscilloscope 2 used with the probe circuit should include a BNC interface 21. Each circuit will be described separately below.

The high-low pass attenuation circuit 11 includes a first input 111, a second input 112 and an output 113, as can be seen in particular in fig. 3. The first input 111 of the high-low pass attenuation circuit 11 is used for connecting with an external circuit 3 to be detected, and receiving a signal to be detected (such as the signal to be detected illustrated in fig. 1) emitted by the circuit 3 to be detected. The high-low pass attenuation circuit 11 is mainly used for performing high-low pass attenuation processing on a signal to be detected received by the first input end 111 to obtain an attenuation signal (such as the attenuation signal illustrated in fig. 1), and outputting the attenuation signal through the output end 113.

The circuit 3 to be detected may be a circuit inside a signal generator or any electronic device, or may be a communication line, a power carrier line, or the like as long as there is an electric signal in the device or line. In addition, the signal to be detected may be a signal in a direct current form or a signal in an alternating current form.

Referring to fig. 1 and 3, the impedance transformation circuit 12 includes an input terminal 121 and an output terminal 122. The input terminal 121 of the impedance transformation circuit 12 is connected to the output terminal 113 of the high-low pass attenuation circuit 11, and the input terminal 121 of the impedance transformation circuit 12 is used for receiving the attenuation signal output from the output terminal 113 of the high-low pass attenuation circuit 11. The impedance transformation circuit 12 is configured to perform impedance transformation on the attenuated signal received by the input terminal 121 to obtain a transformed signal (such as the transformed signal illustrated in fig. 1), and output the transformed signal through the output terminal 122.

It should be noted that the impedance transformation provides a high input impedance for the input end, so that the normal operation of the tested circuit is not disturbed after the tested signal is accessed, and the tested signal is transformed into an output signal with a low output impedance suitable for the input circuit of the oscilloscope, thereby realizing the introduction of the tested signal into the oscilloscope without distortion.

The bias feedback circuit 13 includes an input terminal 131, an output terminal 132, and a configuration terminal 133, see fig. 3 in particular. The input end 131 of the bias feedback circuit 13 is connected to the output end 122 of the impedance transformation circuit 12, and the input end 131 of the bias feedback circuit 13 is used for receiving the transformation signal output by the output end 122 of the impedance transformation circuit 12; the output 132 of the bias feedback circuit 13 is connected to the second input 112 of the high-low pass attenuation circuit 11, and the configuration terminal 133 of the bias feedback circuit 13 is used for receiving a bias configuration signal (such as the bias configuration signal illustrated in fig. 1). The bias feedback circuit 13 is configured to obtain a feedback signal (such as the feedback signal illustrated in fig. 1) according to the bias configuration signal and the transform signal, and output the feedback signal through an output 132 of the bias feedback circuit.

It should be noted that, in one case, the bias configuration signal may be generated by an external controller and sent to the configuration terminal 133 of the bias feedback circuit 13 in the probe circuit 1; in addition, the controller can be controlled by a user, so that a corresponding offset configuration signal is generated according to a control instruction, and the free adjustment function of the offset configuration signal is realized. In another case, the bias configuration signal may be from an oscilloscope 2 used with the probe circuit 1, and the bias configuration signal is generated by a processor in the oscilloscope 2 and sent to the configuration terminal 133 of the bias feedback circuit 13 in the probe circuit 1.

Referring to fig. 1 and 3, the source matching circuit 14 includes an input terminal 141 and an output terminal 142. The input end 141 of the source end matching circuit 14 is connected to the output end 122 of the impedance transformation circuit 12, and the input end 141 of the source end matching circuit 14 is configured to receive a transformation signal output by the output end 122 of the impedance transformation circuit 12; the output 142 of the source matching circuit 14 is used for connecting with the BNC interface 21 of the oscilloscope 2. The source matching circuit 14 is configured to perform impedance transformation on the transformed signal to obtain a coaxial signal (such as the coaxial signal illustrated in fig. 1), so that the coaxial signal has an output impedance matching the characteristic impedance of the coaxial cable and the input impedance of the BNC interface 21 of the oscilloscope 2. Further, the output 142 of the source matching circuit 14 is used to output the coaxial signal.

In the present embodiment, referring to fig. 1, the high-low pass attenuation circuit 11 includes a high-pass attenuation circuit 114 and a low-pass attenuation circuit 115, wherein the high-pass attenuation circuit 114 has an input terminal and an output terminal, and the low-pass attenuation circuit 115 has an input terminal, a comparison terminal and an output terminal. Each is described below.

Referring to fig. 3, an input terminal of the high-pass attenuation circuit 114 and an input terminal of the low-pass attenuation circuit 115 form a first input terminal 111 of the high-low-pass attenuation circuit 11, an output terminal of the high-pass attenuation circuit 114 and an output terminal of the low-pass attenuation circuit 115 form an output terminal 113 of the high-low-pass attenuation circuit 11, and a comparison terminal of the low-pass attenuation circuit 115 serves as a second input terminal 112 of the high-low-pass attenuation circuit 11. That is, the first input 111 of the high-low pass attenuation circuit 11 is used as the input of the high-pass attenuation circuit 114 and also as the input of the low-pass attenuation circuit 115; the output 113 of the high-low pass attenuation circuit 11 is used as the output of the high-pass attenuation circuit 114 and also as the output of the low-pass attenuation circuit 115; the second input terminal 112 of the high low-pass attenuation circuit 11 is used as the comparison terminal of the low-pass attenuation circuit 115.

The high-pass attenuation circuit 114 has the performance of passing high-frequency signals and filtering low-frequency signals, and is mainly used for performing high-pass attenuation processing on a signal to be detected received by an input end (i.e., the first input end 111 of the high-low pass attenuation circuit 11) of the high-pass attenuation circuit to obtain a first attenuation signal (not shown in the figure), and outputting the first attenuation signal through an output end (i.e., the output end 113 of the high-low pass attenuation circuit 11).

The low-pass attenuation circuit 115 has the performance of passing low-frequency signals and filtering high-frequency signals, and is mainly used for performing low-pass attenuation processing on a signal to be detected received at an input end (i.e., the first input end 111 of the high-low-pass attenuation circuit 11) of the low-pass attenuation circuit to obtain a second attenuation signal (not shown in the figure), and outputting the second attenuation signal through an output end (the output end 113 of the high-low-pass attenuation circuit 11). It should be noted that the second attenuation signal and the first attenuation signal herein constitute the attenuation signal output by the output terminal 113 of the high-low pass attenuation circuit 11.

Example II,

Referring to fig. 2 and fig. 3, the present embodiment provides a preferred embodiment based on the probe circuit 1 of the oscilloscope provided in the first embodiment.

In this embodiment, the probe circuit 1 of the oscilloscope includes not only the high-low pass attenuation circuit 11, the impedance transformation circuit 12, the bias feedback circuit 13, the source end matching circuit 14, but also the power supply circuit 15. The power supply circuit 15 is used for supplying dc power to the high-low pass attenuation circuit 11 and the impedance transformation circuit 12, and the circuit structure and the wiring manner can be specifically seen in fig. 2 and 3.

As can be seen from fig. 3, in the case where the high-low pass attenuation circuit 11 includes a source element and the impedance conversion circuit 12 includes a transistor element, these elements are supplied with dc power so that they can normally operate, so that the high-low pass attenuation circuit 11 and the impedance conversion circuit 12 can be supplied with dc power by the power supply circuit 15. For example, the power supply circuit 15 may provide positive dc power (e.g., +5V), negative dc power (e.g., -5V), and ground (e.g., GND ═ 0V).

The positive dc power, the negative dc power, and the ground power provided by the power supply circuit 15 may be provided by independent power sources (such as a battery, a dc power source, a voltage regulator circuit, a linear regulator, etc.), or may be provided by the oscilloscope 2 used in conjunction with the probe circuit 1, and the circuit or the instrument is not limited to be strict as long as the circuit or the instrument can normally provide the positive dc power, the negative dc power, and the ground power.

In the present embodiment, referring to fig. 3, the high-pass attenuation circuit 114 includes a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, and a diode D1. One end of the resistor R5 is used as an input end of the high-pass attenuation circuit 114 (i.e., the first input end 111 of the high-low-pass attenuation circuit 11), the other end of the resistor R5 is connected to one end of the capacitor C2, the other end of the capacitor C2 is used as an output end of the high-pass attenuation circuit 114 (i.e., the output end 113 of the high-low-pass attenuation circuit 11), and the capacitor C1 and the resistor R4 are connected in series and then connected in parallel with a line where the resistor R5 and the. The end of the capacitor C2, which is not connected to the resistor R5, is connected to one end of the capacitor C3, the other end of the capacitor C3 is connected to one end of the resistor R7, the other end of the resistor R7 is connected to the cathode of the diode D1, the anode of the diode D2 is connected to a line (e.g., GND) where the ground power of the power supply circuit 15 is located, the end of the resistor R7 connected to the diode D1 is connected to a line where the ground power of the power supply circuit 15 is located through the resistor R8 and the resistor R9, and the end of the resistor R9, which is opposite to the line where the ground power is located, is connected to a line where the positive dc power of the power supply circuit 15. The end of the capacitor C2 not connected to the resistor R5 is also connected to the ground line of the power supply circuit 15 via the resistor R6 and the capacitor C4.

In one embodiment, the resistor R6 and the resistor R9 are both variable resistors; two invariable ends of the resistor R9 are respectively connected with the positive direct current of the power supply circuit 15 and the line where the grounding electricity is located, and the variable end of the resistor R9 is connected to the end where the resistor R7 and the diode D1 are connected through the resistor R8.

It should be noted that the capacitor C2 in the high-pass attenuation circuit 114 functions as a dc blocking circuit, and can allow the high-frequency part of the signal to be detected to pass through. The capacitor C1, the capacitor C3 and the resistor R4 all play a role in high-frequency compensation. The direct current isolation and the alternating current coupling between the input end and the output end can be realized through the capacitor C1 and the capacitor C2, and the direct current isolation and the alternating current coupling between the output end and the ground end can be realized through the capacitor C3 and the capacitor C4. In addition, the attenuation multiple of the high-pass attenuation circuit 114 at lower frequency can be adjusted by using the variable resistor R6; the variable resistor R9 is used to change the inverse voltage of the varactor diode D1, so as to change the equivalent capacitance of the varactor diode D1, thereby adjusting the attenuation factor of the high-pass attenuation circuit 114 in the high frequency band.

It should be noted that the high-pass attenuation circuit 114 actually performs an ac attenuation function, and can perform attenuation by about N times (for example, N ═ 1, 10) on an ac component present in a signal to be detected, while providing infinite dc input impedance and large ac input impedance. In addition, the high-pass attenuation circuit 114 isolates the input end thereof from the impedance transformation circuit 12, thereby greatly reducing the influence of the lower input impedance in the impedance transformation circuit 12 on the input impedance of the input end of the high-pass attenuation circuit 114, and simultaneously greatly reducing the influence of the input capacitance of the impedance transformation circuit 12 on the input capacitance of the input end of the high-pass attenuation circuit 114.

In the present embodiment, the low-pass attenuation circuit 115 includes a resistor R2, a resistor R3, a resistor R10, and an amplifier U1. One end of the resistor R2 is used as an input end of the low-pass attenuation circuit 115 (i.e., the first input end 111 of the high-low-pass attenuation circuit 11), the other end of the resistor R2 is further connected to a negative input end of the amplifier U1 and one end of the resistor R3, and the other end of the resistor R3 is connected to a line where the ground of the power supply circuit 15 is located. The positive input terminal of the amplifier U1 serves as the second input terminal of the high-low pass attenuation circuit (i.e., the second input terminal 112 of the high-low pass attenuation circuit 11), the output terminal of the amplifier U1 is connected to one terminal of the resistor R10, and the other terminal of the resistor R10 serves as the output terminal of the low-pass attenuation circuit 115 (i.e., the output terminal 113 of the high-low pass attenuation circuit 11). The input end of the low-pass attenuation circuit 115 is connected with the input end of the high-pass attenuation circuit 114, and then is connected with one end of a resistor R1, and the other end of the resistor R1 is used for being connected with an external circuit 3 to be detected.

In the low-pass attenuation circuit 115, the resistor R2 and the resistor R3 play a role of signal attenuation, and are mainly used for realizing attenuation of direct current and low-frequency signals; for example, when the values of the resistor R2 and the resistor R3 are equal to 1M Ω, the dc 1M Ω input impedance of the active probe can be realized. The amplifier U1 may be an integrated operational amplifier commonly used in electronic circuits, such as a field effect output type operational amplifier, which provides an operational amplifier input resistance up to the G Ω level and avoids the effect of the operational amplifier input resistance on the probe dc 1M Ω input impedance. The resistor R10 plays a role of signal isolation, and is mainly used for preventing the high-frequency signal at the input terminal of the impedance transformation circuit 12 from leaking to the output terminal of the amplifier U1. In addition, due to the presence of the amplifier U1 in the low pass attenuation circuit 115, it is possible to provide a direct current and low frequency signal path, to set and provide a stable quiescent operating voltage of the impedance transformation circuit 12, and to provide a path for probe dc biasing using the amplifier U1.

In this embodiment, the impedance transformation circuit 12 includes a transistor Q1, a transistor Q2, a transistor Q3, a resistor R11, a resistor R12, a resistor R13, a resistor R14, and a resistor R15. The control end of the transistor Q1 is used as the input end 121 of the impedance transformation circuit 12, the first end of the transistor Q1 is connected to the control end of the transistor Q2 through the resistor R11, the first end of the transistor Q2 is connected to the control end of the transistor Q3 through the resistor R12, and the first end of the transistor Q3 is used as the output end 122 of the impedance transformation circuit 12. The second ends of the transistor Q1, the transistor Q2, and the transistor Q3 are all connected to a line (for example, a line of +5V) on which a positive dc power of the power supply circuit 15 is located, and the second ends of the transistor Q1, the transistor Q2, and the transistor Q3 are connected to a line (for example, a line of-5V) on which a negative dc power of the power supply circuit 15 is located through a resistor R13, a resistor R14, and a resistor R15, respectively.

It should be noted that the impedance transformation circuit 12 is actually a circuit form formed by three stages of emitter follower, and the first stage emitter follower adopts a radio frequency triode Q1 with low input capacitance, and the input capacitance of the first stage emitter follower can be as low as several pf; the second emitter follower is a radio frequency transistor Q2 for driving the third emitter follower, the third emitter follower is a radio frequency transistor Q3 with strong driving capability, and the radio frequency transistor Q3 is used for driving the source end matching circuit 14 and the input impedance (such as 50 Ω) in the oscilloscope 2. It is understood that the three-stage emitter follower of the impedance transformation circuit 12 is formed by a radio frequency triode, so that the impedance transformation circuit 12 has a bandwidth larger than 4G.

In the present embodiment, the bias feedback circuit 13 includes a resistor R16, a resistor R17, a resistor R18, and a resistor R19. One end of the resistor R16 serves as the input terminal 131 of the bias feedback circuit 13, and the other end serves as the output terminal 132 of the bias feedback circuit 13. The end of the resistor R16 serving as the output end 131 of the bias feedback circuit 13 is connected to one end of the resistor R17, the other end of the resistor R17 is connected to one end of the resistor R19 and one end of the resistor R18, the other end of the resistor R19 is used as the configuration end 133 of the bias feedback circuit 13, and the other end of the resistor R18 is connected to a line (for example, a line of 0V) where the ground power of the power supply circuit 15 is located.

In one embodiment, the resistor R17 is a variable resistor, and the attenuation factor of the low-pass attenuation circuit 115 is adjusted by adjusting the resistance of the resistor R17.

It should be noted that, in the bias feedback circuit 13, the resistors R16, R17, R18, and R19 and the resistors R2 and R3 in the low-pass attenuation circuit 115 commonly set the attenuation multiple of the active direct current and the low frequency, and the attenuation multiple of the low-pass attenuation circuit 115 is finely adjusted by adjusting the variable resistor R17, so that the total attenuation multiple of the low-pass attenuation circuit 115 and the source-side matching circuit 14 reaches a specific value (for example, 10 times). The feedback signal output by the bias feedback circuit 13 has the capability of adjusting the dc bias, and is input from one end of the resistor R19, and the dc bias of the probe is set by the resistors R16, R17, R18 and R19. It is understood that the main function of the bias feedback circuit 13 is to provide a large loop negative feedback of the operational amplifier U1 and the impedance transformation circuit 12, so that the operational amplifier U1 and the impedance transformation circuit 12 can operate stably.

In the present embodiment, the source terminal matching circuit 14 includes a resistor R20, a resistor R21, and a capacitor C5. Two ends of the resistor R20 are respectively used as the input terminal 141 and the output terminal 142 of the source end matching circuit 14, and the resistor R21 and the capacitor C5 are connected in series and then connected in parallel with the resistor R20.

It should be noted that, in the source end matching circuit 14, the resistor R20 plays a role of impedance matching, and the resistor R21 and the capacitor C5 play a role of high frequency compensation, and are mainly used for compensating for the change of the output impedance of the third-stage emitter follower (i.e., the transistor Q3) in the high frequency impedance transformation circuit 12 with the frequency. It will be appreciated that the source matching circuit 14 is designed such that the sum of the output resistance of the third emitter follower (i.e., transistor Q3) of the impedance transformation circuit 12 and the resistor R20 is a specific impedance (e.g., 50 Ω) that can be matched to the impedance elements (e.g., 50 Ω) in the BNC interface 21 of the oscilloscope 2.

In this embodiment, by adjusting the variable resistor R6 and the variable resistor R9 in the high-pass attenuation circuit 114, the total attenuation multiple of the high-pass attenuation circuit 114, the impedance transformation circuit 12, and the source-side matching circuit 14 can reach a specific value (for example, 10 times).

It will be appreciated by those skilled in the art that the following technical advantages may be achieved when applying the single-ended active probe 1 disclosed in the present embodiment: (1) the signal to be detected is transmitted to the impedance transformation network after being subjected to amplitude attenuation through the high-low pass attenuation circuit, so that the signal to be detected can be received by the high-low pass attenuation circuit even if the signal to be detected has a larger input signal range, and the detection of the signal with the larger input signal range is facilitated; (2) the triode is used in the impedance transformation circuit to replace the traditional field effect transistor, so that the impedance transformation circuit has smaller input capacitance and plays a role in reducing the input capacitance of the active probe; (3) the high-low pass attenuation circuit isolates the circuit to be detected and the impedance conversion circuit, and the circuit structure avoids the impedance conversion circuit from being directly exposed at the input side of the signal to be detected, so that the input capacitance of the probe can be greatly reduced, and the probe has higher bandwidth; (4) the bias feedback circuit is provided with a configuration end, so that the bias feedback circuit can receive a bias configuration signal from the controller, and then processes the conversion signal under the action of the bias configuration signal to obtain a feedback signal, simultaneously realizes the purpose of freely adjusting the direct current bias, and overcomes the problem that the direct current bias of the conventional oscilloscope probe is not adjustable; (5) the rear end of the impedance transformation circuit is provided with the source end matching circuit, so that the reflection problem of a signal in the coaxial transmission process can be reduced by means of the source end matching circuit, the signal amplitude and the flatness are better, and the signal bandwidth required by coaxial signal transmission can be ensured; (6) the probe circuit comprises a high-pass attenuation circuit, a low-pass attenuation circuit, an impedance conversion circuit, a bias feedback circuit and a source end matching circuit, so that when the probe circuit processes a signal to be detected, the probe circuit has excellent performances of higher bandwidth, larger input signal range and smaller input capacitance, and the performance of the active probe is greatly improved.

Example III,

Referring to fig. 4, on the basis of the probe circuit 1 of the oscilloscope disclosed in the second embodiment, a preferred embodiment is further provided, so that the probe circuit 1 and the oscilloscope 2 can be effectively used in cooperation with each other. The oscilloscope 2 should include a BNC interface 21 and a communication interface 22, so that when the probe circuit 1 and the oscilloscope 2 are used cooperatively, the bias configuration signal and the direct current required for operation (i.e., the positive direct current, the negative direct current, and the ground current provided in the power supply circuit 15) are acquired from the communication interface 22 of the oscilloscope 2, and a coaxial signal is also sent to the BNC interface of the oscilloscope 2.

In this embodiment, referring to fig. 4, the output 142 of the source matching circuit 14 may form a first probe interface 16, and the first probe interface 16 is configured to be adapted to the BNC interface 21 of the oscilloscope 2 and output an on-axis signal to the BNC interface 21 of the oscilloscope 2. In one case, in order to facilitate an effective connection between the first probe interface 16 and the BNC interface 21, a single-channel coaxial cable may be further disposed between the output end 142 of the source end matching circuit 14 and the first probe interface 16, where the coaxial cable has a certain characteristic impedance, so that the coaxial signal is transmitted on an inner coaxial line of the coaxial cable, and meanwhile, an external shielding layer of the coaxial cable is used to shield interference of an environmental electromagnetic signal, so that the first probe interface 16 can be arbitrarily pulled to be connected to the BNC interface of the oscilloscope 2.

In this embodiment, when the first probe interface 16 is adaptively connected to the BNC interface 21 of the oscilloscope 2, the first probe interface 16 and the BNC interface 21 are required to satisfy the same interface type of BNC (bayonet Nut connector). Referring to fig. 5, the first probe interface 16 may adopt a single-channel BNC connector, and has a shielding layer 161 on the outside and a coaxial line 162 on the inside, where the shielding layer 161 can prevent electromagnetic waves in the environment from interfering with coaxial signals transmitted on the coaxial line 162, and functions as an electromagnetic shield. If the first probe interface 16 is a male, the BNC interface 21 should be a female adapted to the male. Since the interface type of BNC is a well-established technology, it will not be described in detail here.

In this embodiment, referring to fig. 4, the configuration terminal 133 of the bias feedback circuit 13 and the line where the positive direct current, the negative direct current, and the ground of the power supply circuit 15 are located are combined to form a second probe interface 17, and the second probe interface 17 is adapted to the communication interface 22 of the oscilloscope 15 and receives the direct current and the bias configuration signal output by the communication interface 22 of the oscilloscope 2. Specifically, the second probe interface 17 may have a plurality of pins, wherein one of the pins functions as a data line and transmits a bias configuration signal, and wherein three of the pins respectively function as a positive power line, a negative power line, and a ground line and cooperate to transmit positive direct current, negative direct current, and ground.

It should be noted that the BNC interface 21 (also called as BNC Connector for Bayonet Nut Connector) of the oscilloscope is a Connector for coaxial cables, and at present, the BNC interface is widely used in communication systems, for example, the E1 interface in network equipment is connected by coaxial cables of two BNC connectors, and is also often used for transmitting audio and video signals in high-grade monitors and audio equipment. The communication interface 22 of the oscilloscope 2 may adopt an existing standard communication interface (for example, RS232, RS485, VGA, GPIB or HDMI is a standard communication interface), or may adopt a communication interface of a custom interface type and a communication protocol, which is not limited herein.

In one embodiment, the second probe interface 17 of the probe circuit 1 may employ the customized pin arrangement of FIG. 6. Referring to fig. 6, the second probe interface 17 includes multiple pins, wherein one pin (e.g., pin 3) is used as a data line and transmits an analog bias configuration signal, and three pins (e.g., pins 5, 6, and 1) constitute an input terminal of the power supply circuit 15 and are respectively used as a positive power line, a negative power line, and a ground line and cooperate to transmit dc power. In addition, two pins (such as pin 2 and pin 4) are arranged in a floating mode and do not transmit signals or supply power. The communication interface 22 of the oscilloscope 2 should then be adapted to the second probe interface, one forming a male and the other forming a female.

It can be understood by those skilled in the art that when the single-ended active probe 1 disclosed in this embodiment is used in conjunction with the oscilloscope 2, the probe circuit can effectively process the signal to be detected and make the generated coaxial signal have an output impedance matched with the characteristic impedance of the coaxial cable and the input impedance of the BNC interface of the oscilloscope, and the oscilloscope can receive and digitally analyze the coaxial signal and effectively control the bias feedback process inside the probe circuit, so as to enhance the detection performance of the signal detection system on the signal to be detected under the cooperation of the probe circuit and the oscilloscope.

Those skilled in the art will appreciate that all or part of the functions of the various methods in the above embodiments may be implemented by hardware, or may be implemented by computer programs. When all or part of the functions of the above embodiments are implemented by a computer program, the program may be stored in a computer-readable storage medium, and the storage medium may include: a read only memory, a random access memory, a magnetic disk, an optical disk, a hard disk, etc., and the program is executed by a computer to realize the above functions. For example, the program may be stored in a memory of the device, and when the program in the memory is executed by the processor, all or part of the functions described above may be implemented. In addition, when all or part of the functions in the above embodiments are implemented by a computer program, the program may be stored in a storage medium such as a server, another computer, a magnetic disk, an optical disk, a flash disk, or a removable hard disk, and may be downloaded or copied to a memory of a local device, or may be version-updated in a system of the local device, and when the program in the memory is executed by a processor, all or part of the functions in the above embodiments may be implemented.

The present invention has been described in terms of specific examples, which are provided to aid understanding of the invention and are not intended to be limiting. For a person skilled in the art to which the invention pertains, several simple deductions, modifications or substitutions may be made according to the idea of the invention.

Claims

1. A probe circuit of an oscilloscope comprises a BNC interface, and is characterized in that the probe circuit comprises a high-low pass attenuation circuit, an impedance conversion circuit, a bias feedback circuit and a source end matching circuit;

the high-low pass attenuation circuit comprises a first input end, a second input end and an output end, wherein the first input end of the high-low pass attenuation circuit is used for being connected with an external circuit to be detected and receiving a signal to be detected transmitted by the circuit to be detected; the high-low pass attenuation circuit is used for carrying out high-low pass attenuation processing on the signal to be detected received by the first input end of the high-low pass attenuation circuit to obtain an attenuation signal, and outputting the attenuation signal through the output end of the high-low pass attenuation circuit;

the impedance conversion circuit comprises an input end and an output end, wherein the input end of the impedance conversion circuit is connected with the output end of the high-low pass attenuation circuit and is used for receiving the attenuation signal; the impedance transformation circuit is used for carrying out impedance transformation on the attenuation signal received by the input end of the impedance transformation circuit to obtain a transformation signal and outputting the transformation signal through the output end of the impedance transformation circuit;

the bias feedback circuit comprises an input end, an output end and a configuration end, wherein the input end of the bias feedback circuit is connected with the output end of the impedance transformation circuit and used for receiving the transformation signal, the output end of the bias feedback circuit is connected with the second input end of the high-low pass attenuation circuit, and the configuration end of the bias feedback circuit is used for receiving a bias configuration signal; the bias feedback circuit is used for obtaining a feedback signal according to the bias configuration signal and the conversion signal and outputting the feedback signal through an output end of the bias feedback circuit;

the source end matching circuit comprises an input end and an output end, and the input end of the source end matching circuit is connected with the output end of the impedance transformation circuit and used for receiving the transformation signal; the output end of the source end matching circuit is used for being connected with a BNC interface of the oscilloscope; the source end matching circuit is used for performing impedance transformation on the transformed signal to obtain a coaxial signal, so that the coaxial signal has output impedance matched with the characteristic impedance of a coaxial cable and the input impedance of a BNC interface; and the output end of the source end matching circuit is used for outputting the coaxial signal.

2. The oscilloscope probe circuit according to claim 1, wherein said high low pass attenuation circuit comprises a high pass attenuation circuit and a low pass attenuation circuit;

the high-pass attenuation circuit has an input end and an output end;

the low-pass attenuation circuit is provided with an input end, a comparison end and an output end; the input end of the high-pass attenuation circuit and the input end of the low-pass attenuation circuit form a first input end of the high-low-pass attenuation circuit, the output end of the high-pass attenuation circuit and the output end of the low-pass attenuation circuit form an output end of the high-low-pass attenuation circuit, and the comparison end of the low-pass attenuation circuit is used as a second input end of the high-low-pass attenuation circuit;

the high-pass attenuation circuit is used for carrying out high-pass attenuation processing on the signal to be detected received by the input end of the high-pass attenuation circuit to obtain a first attenuation signal and outputting the first attenuation signal through the output end of the high-pass attenuation circuit;

the low-pass attenuation circuit is used for performing low-pass attenuation processing on the signal to be detected received by the input end of the low-pass attenuation circuit to obtain a second attenuation signal and outputting the second attenuation signal through the output end of the low-pass attenuation circuit; wherein the second attenuated signal and the first attenuated signal constitute the attenuated signal.

3. The oscilloscope probe circuit according to claim 2, further comprising a power supply circuit for dc supplying said high low pass attenuation circuit and said impedance transformation circuit.

4. The oscilloscope probe circuit according to claim 3, wherein the high pass attenuation circuit comprises a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4 and a diode D1;

one end of the resistor R5 is used as the input end of the high-pass attenuation circuit, the other end of the resistor R5 is connected with one end of the capacitor C2, the other end of the capacitor C2 is used as the output end of the high-pass attenuation circuit, and the capacitor C1 and the resistor R4 are connected in series and then are connected in parallel with a circuit where the resistor R5 and the capacitor C2 are located;

the end, which is not connected with the resistor R5, of the capacitor C2 is connected with one end of the capacitor C3, the other end of the capacitor C3 is connected with one end of the resistor R7, the other end of the resistor R7 is connected with the cathode of the diode D1, the anode of the diode D2 is connected with a line where the grounding electricity of the power supply circuit is located, the end, which is connected with the diode D1, of the resistor R7 is connected with the line where the grounding electricity of the power supply circuit is located through the resistor R8 and the resistor R9, and the end, which is opposite to the line where the grounding electricity is located, of the resistor R9 is connected with the line where the anode direct current of the power supply;

the end of the capacitor C2, which is not connected with the resistor R5, is also connected with a line where the grounding of the power supply circuit is located through the resistor R6 and the capacitor C4.

5. The oscilloscope probe circuit according to claim 4, wherein said resistor R6 and said resistor R9 are both variable resistors; the two unchangeable ends of the resistor R9 are respectively connected with the circuits where the positive direct current and the grounding current of the power supply circuit are located, and the variable end of the resistor R9 is connected to the end where the resistor R7 and the diode D1 are connected through the resistor R8.

6. The oscilloscope probe circuit according to claim 3, wherein the low pass attenuation circuit comprises a resistor R2, a resistor R3, a resistor R10 and an amplifier U1;

one end of the resistor R2 is used as the input end of the low-pass attenuation circuit, the other end of the resistor R2 is respectively connected with the negative input end of the amplifier U1 and one end of the resistor R3, and the other end of the resistor R3 is connected to a circuit where the grounding electricity of the power supply circuit is located;

the positive input end of the amplifier U1 is used as the second input end of the high-low pass attenuation circuit, the output end of the amplifier U1 is connected with one end of a resistor R10, and the other end of the resistor R10 is used as the output end of the low-pass attenuation circuit;

the input end of the low-pass attenuation circuit is connected with the input end of the high-pass attenuation circuit and then is connected with one end of a resistor R1, and the other end of the resistor R1 is used for being connected with an external circuit to be detected.

7. The oscilloscope probe circuit according to claim 3, wherein the impedance transformation circuit comprises a transistor Q1, a transistor Q2, a transistor Q3, a resistor R11, a resistor R12, a resistor R13, a resistor R14, and a resistor R15;

the control end of the triode Q1 is used as the input end of the impedance transformation circuit, the first end of the triode Q1 is connected with the control end of the triode Q2 through a resistor R11, the first end of the triode Q2 is connected with the control end of the triode Q3 through a resistor R12, and the first end of the triode Q3 is used as the output end of the impedance transformation circuit;

second ends of the triode Q1, the triode Q2 and the triode Q3 are all connected with a circuit where positive direct current of the power supply circuit is located, and second ends of the triode Q1, the triode Q2 and the triode Q3 are respectively connected with a circuit where negative direct current of the power supply circuit is located through a resistor R13, a resistor R14 and a resistor R15.

8. The oscilloscope probe circuit according to claim 3, wherein the bias feedback circuit comprises a resistor R16, a resistor R17, a resistor R18, and a resistor R19;

one end of the resistor R16 is used as the input end of the bias feedback circuit, and the other end is used as the output end of the bias feedback circuit; the end of the resistor R16, which is used as the output end of the bias feedback circuit, is connected with one end of the resistor R17, the other end of the resistor R17 is respectively connected with one end of the resistor R19 and one end of the resistor R18, the other end of the resistor R19 is used as the configuration end of the bias feedback circuit, and the other end of the resistor R18 is connected with a line where the grounding electricity of the power supply circuit is located; the resistor R17 is a variable resistor.

9. The oscilloscope probe circuit according to claim 3, wherein the source end matching circuit comprises a resistor R20, a resistor R21 and a capacitor C5;

two ends of the resistor R20 are respectively used as an input end and an output end of the source end matching circuit, and the resistor R21 and the capacitor C5 are connected in series and then connected in parallel with the resistor R20.

10. The oscilloscope probe circuit according to any one of claims 3-9, wherein said oscilloscope further comprises a communication interface, wherein the output of said source matching circuit constitutes a first probe interface, said first probe interface being adapted to a BNC interface of an oscilloscope and outputting said coaxial signal to said BNC interface of said oscilloscope;

the configuration end of the bias feedback circuit and a circuit where a positive direct current, a negative direct current and a grounding current of the power supply circuit are located are combined to form a second probe interface, and the second probe interface is used for being matched with a communication interface of the oscilloscope and receiving direct current and bias configuration signals output by the communication interface of the oscilloscope.