Differential probe

Abstract

According to the differential probe, a low-frequency-band signal and a high-frequency-band signal in differential input signals are subjected to gain amplification through a low-frequency amplification module and a high-frequency amplification module respectively, and the gain amplification times of the low-frequency amplification module and the high-frequency amplification module are controlled and adjusted through gain amplification control signals. A relay does not need to be used for adjusting a gain amplification factor gear, so that a differential input signal with a relatively high voltage can be measured, and a relatively high bandwidth is achieved.

Description

Technical Field

[0001] This application relates to the field of probe technology, specifically to a differential probe. Background Technology

[0002] When measuring differential signals, oscilloscopes and other measuring devices typically use differential probes. Currently, differential probes can be divided into two categories based on the voltage of the signal being measured: one category is for low voltages, measuring voltages less than ±8V, with only one attenuation level and a bandwidth greater than 1GHz; the other category is for high voltages, measuring voltages in the kV range and a bandwidth less than 200MHz.

[0003] Please refer to Figure 1 , Figure 1 The diagram illustrates the structure of a differential probe designed for low voltage. An attenuation circuit reduces the input signal voltage before it is amplified into a single-ended signal. For high-voltage differential probes, high-power devices are used to build the attenuation circuit, allowing for a wider input voltage range. Adding a relay to the attenuation circuit enables switching between attenuation levels. However, high-power devices typically have large packages and significant parasitic effects, and relays limit bandwidth, resulting in a generally low bandwidth for differential probes.

[0004] In summary, there is a certain demand for differential probes that can measure higher voltages and have higher bandwidth. Utility Model Content

[0005] This application provides a differential probe capable of measuring higher voltages and with a higher bandwidth.

[0006] According to one aspect of this application, one embodiment provides a differential probe, including: two signal processing links, a low-frequency amplification module, a high-frequency amplification module, and a differential-to-single-ended module;

[0007] Each of the signal processing links is used to receive one differential input signal and process the received differential input signal, the processing including at least signal attenuation processing, AC coupling processing and impedance transformation processing;

[0008] The output of the low-frequency amplification module is connected to either of the two signal processing links; the low-frequency amplification module receives two differential input signals and, in response to a gain amplification control signal, performs a first gain amplification on the low-frequency signal of the two differential input signals, outputting a single low-frequency signal after gain amplification, wherein the amplification factor of the first gain amplification is associated with the gain amplification control signal; the single low-frequency signal after gain amplification is transmitted to the high-frequency amplification module by at least a portion of a signal processing link connected to the low-frequency amplification module; the low-frequency signal is a signal with a frequency lower than a first frequency;

[0009] The input terminal of the high-frequency amplification module is connected to the two signal processing links, and the output terminal of the high-frequency amplification module is connected to the input terminal of the differential-to-single-ended module. The high-frequency amplification module, in response to the gain amplification control signal, performs a second gain amplification on the high-frequency signals of the two signals output from the two signal processing links, and outputs the two amplified high-frequency signals to the differential-to-single-ended module. The amplification factor of the second gain amplification is related to the gain amplification control signal. The high-frequency signal is a signal with a frequency greater than a second frequency, where the second frequency is greater than or equal to the first frequency.

[0010] The differential-to-single-ended module is used to perform differential-to-single-ended processing on the two signals output from the two signal processing links respectively, and output a single-ended output signal.

[0011] In one embodiment, the low-frequency amplification module includes an attenuation unit, a first operational amplification unit, and a second operational amplification unit;

[0012] The attenuation unit is used to attenuate the received two differential input signals;

[0013] The first operational amplifier unit has a first input terminal and a second input terminal. The first input terminal and the second input terminal are connected to the output terminal of the attenuation unit. The first operational amplifier unit is used to perform differential-to-single-ended conversion and impedance transformation processing on the low-frequency signal acquired by its first input terminal and the low-frequency signal acquired by its second input terminal, so as to output a low-frequency signal.

[0014] The second operational amplifier unit is connected to the output terminal of the first operational amplifier unit. The second operational amplifier unit is used to perform a first gain amplification on the low-frequency signal according to the amplification factor corresponding to the gain amplification control signal, so as to output a low-frequency signal after gain amplification.

[0015] In one embodiment, the attenuation unit includes: resistors R12, R13, R14, and R15. One end of resistor R12 is used to receive one differential input signal, and the other end of resistor R12 is connected to one end of resistor R13. The other end of resistor R13 is connected to ground, and the end where resistors R12 and R13 are connected is used to output the attenuated differential input signal. One end of resistor R14 is used to receive another differential input signal, and the other end of resistor R14 is connected to one end of resistor R15. The other end of resistor R15 is used to output the attenuated differential input signal; and / or,

[0016] The first operational amplifier unit includes an operational amplifier U1, a resistor R16 and a resistor R17. The positive input terminal of the operational amplifier U1 is used to acquire one differential input signal, and the negative input terminal of the operational amplifier U1 is used to acquire another differential input signal. The output terminal and the negative input terminal of the operational amplifier U1 are connected in series with the resistor R16 and the resistor R17. The output terminal of the operational amplifier U1 is used to output a low-frequency signal.

[0017] The second operational amplifier unit includes an operational amplifier U2, resistors R18, R19, R20, and R21, and a switch S3. One end of resistor R18 is connected to the first terminal of switch S3. The end of resistor R18 connected to switch S3 is used to receive a low-frequency signal. The other end of resistor R18 is connected to the negative input terminal of operational amplifier U2. The second terminal of switch S3 is connected to one end of resistor R20. The other end of resistor R20 is connected to the negative input terminal of operational amplifier U2. Resistor R19 is connected between the negative input terminal and the output terminal of operational amplifier U2. The positive input terminal of operational amplifier U2 is connected to ground. The output terminal of operational amplifier U2 is connected to one end of resistor R21. The other end of resistor R21 is used to output a low-frequency signal after gain amplification. Switch S3 has a control terminal, which is used to control the first and second terminals of switch S3 to close or open in response to the gain amplification control signal.

[0018] In one embodiment, the high-frequency amplification module includes: a first amplifier, a second amplifier, and a high-frequency gain control unit;

[0019] The first amplifier is connected to a signal processing link, and the first amplifier is used to perform a second gain amplification on the high-frequency signal output by the signal processing link connected to it, so as to output a high-frequency signal after gain amplification.

[0020] The second amplifier is connected to another signal processing link. The second amplifier is used to perform a second gain amplification on the high-frequency signal output by the signal processing link connected to it, so as to output another high-frequency signal after gain amplification.

[0021] The high-frequency gain control unit is connected to the first amplifier and the second amplifier. The high-frequency gain control unit is used to adjust the amplification factor of the first amplifier and the second amplifier for second gain amplification based on the gain amplification control signal.

[0022] In one embodiment, the first amplifier includes switching transistors Q3 and Q5, resistors R22 and R24, and a constant current source I1. One end of resistor R22 is connected to a signal processing link, and the other end of resistor R22 is connected to the second terminal of switching transistor Q3. The control terminal of switching transistor Q3 is connected to a voltage source V2. The first terminal of switching transistor Q3 is connected to the control terminal of switching transistor Q5, one end of resistor R24, and the other end of resistor R24 ​​is connected to the voltage supply terminal VCC. The first terminal of switching transistor Q5 is connected to the voltage supply terminal VCC, and the second terminal of switching transistor Q5 is connected to the voltage supply terminal VEE through the constant current source I1. The second terminal of switching transistor Q5 is used to output a high-frequency signal; and / or

[0023] The second amplifier includes switching transistors Q4 and Q6, resistors R23 and R25, and a constant current source I2. One end of resistor R23 is connected to another signal processing link, and the other end of resistor R23 is connected to the second terminal of switching transistor Q4. The control terminal of switching transistor Q4 is connected to a voltage source V2. The first terminal of switching transistor Q4 is connected to the control terminal of switching transistor Q6 and one end of resistor R25. The other end of resistor R25 is connected to the voltage supply terminal VCC. The first terminal of switching transistor Q6 is connected to the voltage supply terminal VCC. The second terminal of switching transistor Q6 is connected to the voltage supply terminal VEE through the constant current source I2. The second terminal of switching transistor Q6 is used to output a high-frequency signal; and / or,

[0024] The high-frequency gain control unit includes diodes D1 and D2, resistors R26, R27, R28, and R29, capacitor C4, and switching transistor Q7. One end of resistor R26 is connected to the first amplifier, and the other end of resistor R26 is connected to the cathode of diode D1. The anode of diode D1 is connected to the anode of diode D2. The cathode of diode D2 is connected to one end of resistor R27, and the other end of resistor R27 is connected to the second amplifier. The anodes of diodes D1 and D2 are connected to one end of capacitor C4 and the second terminal of switching transistor Q7. The other end of capacitor C4 is connected to ground. The first terminal of switching transistor Q7 is connected to the voltage supply terminal VCC through resistor R29, and the control terminal of switching transistor Q7 receives the gain amplification control signal through resistor R28.

[0025] In one embodiment, each of the signal processing links includes: an attenuation module, an AC coupling module, and an impedance transformation module;

[0026] The attenuation module is used to attenuate the received differential input signal and output the attenuated differential signal.

[0027] The AC coupling module is connected between the output of the attenuation module and the input of the impedance transformation module; the AC coupling module is used to extract and output the AC component of the attenuated differential signal to the impedance transformation module.

[0028] The impedance transformation module is used to provide the output impedance within a preset range and transmit the AC component of the received attenuated differential signal to the high-frequency amplification module.

[0029] In one embodiment, the output of the low-frequency amplification module is connected to the input of the impedance transformation module in either of the two signal processing links.

[0030] The impedance transformation module is also used to transmit one low-frequency signal output by the low-frequency amplification module to the high-frequency amplification module.

[0031] In one embodiment, the attenuation module includes resistors R1, R2, R3, and R4, and capacitors C1 and C2. One end of resistor R1 is used to receive a differential input signal, and the other end of resistor R1 is connected to one end of resistor R3 and one end of capacitor C2. The other end of resistor R3 is connected to ground, and the other end of capacitor C2 is connected to ground through resistor R4. One end of capacitor C1 is connected to one end of resistor R1, and the other end of capacitor C1 is connected to one end of resistor R2. The other end of resistor R2 is connected to the other end of resistor R1. The end where resistors R1, R2, R3, and capacitor C2 are connected is used to output the attenuated differential signal; and / or,

[0032] The AC coupling module includes a capacitor C3. One end of the capacitor C3 is used to receive the attenuated differential signal, and the other end of the capacitor C3 is used to output the AC component of the attenuated differential signal.

[0033] In one embodiment, the impedance transformation module includes: a switch Q1, resistors R5, R6, R7, and R8. One end of resistor R5 and one end of resistor R8 are used to receive input signals. The other end of resistor R8 is connected to a voltage source V1. The other end of resistor R5 is connected to the control terminal of switch Q1. The first terminal of switch Q1 is connected to the voltage supply terminal VCC through resistor R6, and the second terminal of switch Q1 is connected to the voltage supply terminal VEE through resistor R7. The second terminal of switch Q1 is used to output signals; or...

[0034] The impedance transformation module includes: a switch Q1, a switch Q2, resistors R5, R7, R8, R9, R10, and R11. One end of resistor R5 and one end of resistor R8 are used to receive the input signal. The other end of resistor R8 is connected to a voltage source V1. The other end of resistor R5 is connected to the control terminal of switch Q1. The first terminal of switch Q1 is connected to the voltage supply terminal VCC through resistor R6. The second terminal of switch Q1 is connected to the voltage supply terminal VEE through resistor R7. The second terminal of switch Q1 is connected to one end of resistor R9. The other end of resistor R9 is connected to the control terminal of switch Q2. The first terminal of switch Q2 is connected to the voltage supply terminal VCC through resistor R10. The second terminal of switch Q2 is connected to the voltage supply terminal VEE through resistor R11. The second terminal of switch Q2 is used to output the signal.

[0035] In one embodiment, it further includes:

[0036] The controller is used to generate the gain amplification control signal and output the gain amplification control signal to the low-frequency amplification module and the high-frequency amplification module.

[0037] According to the differential probe of the above embodiment, the low-frequency signal and the high-frequency signal in the differential input signal are amplified by the low-frequency amplification module and the high-frequency amplification module, respectively. Furthermore, the gain amplification factor of the low-frequency amplification module and the high-frequency amplification module are controlled and adjusted by the gain amplification control signal, without the need to use a relay to adjust the gain amplification factor level. This allows for the measurement of differential input signals with higher voltages and also provides a higher bandwidth. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of an existing differential probe.

[0039] Figure 2 This is a schematic diagram of the differential probe provided in an embodiment of this application;

[0040] Figure 3 This is a schematic diagram of the signal processing link structure according to one embodiment;

[0041] Figure 4 This is a circuit diagram of an attenuation module according to one embodiment;

[0042] Figure 5 This is a circuit diagram of an impedance transformation module according to one embodiment;

[0043] Figure 6 This is a schematic diagram of the impedance transformation module according to another embodiment;

[0044] Figure 7 This is a circuit diagram of a low-frequency amplifier module according to one embodiment;

[0045] Figure 8 This is a schematic diagram of the structure of a high-frequency amplification module according to one embodiment;

[0046] Figure 9 This is a partial circuit diagram of a high-frequency amplifier module according to one embodiment;

[0047] Figure 10 This is a partial circuit diagram of a high-frequency amplifier module according to one embodiment;

[0048] Figure 11 This is a circuit diagram of a differential-to-single-ended module according to one embodiment. Detailed Implementation

[0049] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments. Similar elements in different embodiments are referred to by related similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0050] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments, and the operational steps involved in each embodiment can also be rearranged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the specification and drawings are only for clearly describing a particular embodiment and do not imply that they represent the necessary components and / or order.

[0051] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0052] This application provides a differential probe, which is used in measuring equipment such as oscilloscopes. Taking an oscilloscope as an example, the output end of the differential probe is connected to the input channel of the oscilloscope through a coaxial cable, and the input end of the differential probe is connected to the circuit under test through a coaxial cable to obtain two differential input signals.

[0053] Please refer to Figure 2Some embodiments of the differential probe include: two signal processing links 101, a low-frequency amplification module 102, a high-frequency amplification module 103, and a differential-to-single-ended module 104. The input terminals of the two signal processing links 101 are connected to the circuit under test via coaxial cables. The output terminals of both signal processing links 101 are connected to the input terminals of the high-frequency amplification module 103. The output terminal of the high-frequency amplification module 103 is connected to the input terminal of the differential-to-single-ended module 104. The input terminal of the low-frequency amplification module 102 is connected to the input terminals of both signal processing links 101, and the output terminal of the low-frequency amplification module 102 is connected to either of the two signal processing links 101. The output terminal of the differential-to-single-ended module 104 is connected to a measuring device via a coaxial cable. The various modules are described in detail below.

[0054] Each signal processing link 101 is used to receive one differential input signal and process the received differential input signal. This processing may include at least signal attenuation, AC coupling, and impedance transformation. Specifically, two signal processing links 101 are used to receive one positive differential input signal and one negative differential input signal, respectively, and these two differential input signals form a set of differential input signals. It should be noted that the two signal processing links 101 have the same circuit structure.

[0055] The low-frequency amplification module 102 receives two differential input signals and, in response to a gain amplification control signal, performs a first gain amplification on the low-frequency signal in the two differential input signals, outputting a single low-frequency signal after gain amplification. The amplification factor of the first gain amplification is related to the gain amplification control signal; and the single low-frequency signal after gain amplification is transmitted to the high-frequency amplification module 103 by at least a portion of a module in a signal processing link connected to the low-frequency amplification module 102; the low-frequency signal is a signal with a frequency lower than a first frequency.

[0056] The high-frequency amplification module 103 is used to respond to the gain amplification control signal to perform a second gain amplification on the high-frequency signals of the two signals output from the two signal processing links 101 respectively, and output the two high-frequency signals after gain amplification to the differential-to-single-ended module 104. The amplification factor of the second gain amplification is related to the gain amplification control signal; the high-frequency signal is a signal with a frequency greater than the second frequency, and the second frequency is greater than or equal to the first frequency.

[0057] The differential-to-single-ended module 104 is used to perform differential-to-single-ended processing on the two signals output from the two signal processing links respectively, and output a single-ended output signal.

[0058] With the differential probe provided above, the gain amplification of the differential input signal is adjusted by the gain amplification control signal, eliminating the need for relay switching. Furthermore, the high-frequency and low-frequency signals are amplified separately, enabling the measurement of differential input signals with higher voltages and providing a higher bandwidth.

[0059] The following provides some embodiments of the specific circuits of each module in the differential probe described above. It should be noted that the circuits of each module in the differential probe provided in this application are not limited to the following embodiments.

[0060] Please refer to Figure 3 In some embodiments, each signal processing link 101 includes an attenuation module 201, an AC coupling module 202, and an impedance transformation module 203. The input terminal of the attenuation module 201 is used to receive a differential input signal. The AC coupling module 202 is connected between the output terminal of the attenuation module 201 and the input terminal of the impedance transformation module 203. The output terminal of the impedance transformation module 203 serves as the output terminal of the signal processing link 101, which is connected to the high-frequency amplification module 103.

[0061] The attenuation module 201 is used to attenuate the received differential input signal and output the attenuated differential signal. In this way, when the voltage of the received differential input signal is large, it can be attenuated into a signal with a smaller voltage by the attenuation module 201.

[0062] The AC coupling module 202 is used to extract and output the AC component of the attenuated differential signal to the impedance transformation module 203. The extracted AC component can be an AC signal with a frequency greater than 0 or a frequency greater than a certain small value. The AC coupling module 202 prevents the common-mode voltage in the differential input signal from being directly applied to the impedance transformation module 203. Changes in the common-mode voltage in the differential input signal can affect the operating state of the impedance transformation module 203, resulting in a very small common-mode input range for the differential probe.

[0063] Impedance transformation module 203 is used to provide the output impedance within a preset range and transmit the AC component of the received attenuated differential signal to high-frequency amplification module 103. Since attenuation module 201 is generally composed of large resistors and has a very high output impedance, it is not easy to set the amplification factor if it is directly connected to high-frequency amplification module 103. Therefore, impedance transformation module 203 is needed to reduce the output impedance of attenuation module 201 before connecting it to high-frequency amplification module 103.

[0064] In some embodiments, since the high-frequency amplification module 103 can only control the gain of the high-frequency signal, the gain of the low-frequency signal needs to be achieved by the low-frequency amplification module 102. The output terminal of the low-frequency amplification module 102 is connected to the input terminal of the impedance transformation module 203 in either of the two signal processing links, so that the low-frequency amplification module 102 takes the differential input signal from the input terminal, amplifies it, and then inputs it to the impedance transformation module 203. The impedance transformation module 203 is also used to transmit one low-frequency signal output by the low-frequency amplification module 102 to the high-frequency amplification module 103. The high-frequency amplification module 103 only amplifies the gain of the high-frequency signal and will directly transmit one low-frequency signal to the differential-to-single-ended module 104.

[0065] Please refer to Figure 4 In some embodiments, the attenuation module 201 includes resistors R1, R2, R3, and R4, and capacitors C1 and C2. One end of resistor R1 receives a differential input signal PA, where PA is a positive differential input signal. The other end of resistor R1 is connected to one end of resistor R3 and one end of capacitor C2. The other end of resistor R3 is connected to ground, and the other end of capacitor C2 is connected to ground through resistor R4. One end of capacitor C1 is connected to one end of resistor R1, and the other end of capacitor C1 is connected to one end of resistor R2. The other end of resistor R2 is connected to the other end of resistor R1. The end where resistors R1, R2, R3, and C2 are connected is used to output the positive attenuated differential signal PB. In the above circuit, resistors R1 and R3 form a basic resistor divider circuit to attenuate the voltage of the input differential signal, and capacitors C1, R2, R4, and C2 provide high-frequency compensation.

[0066] In some embodiments, the AC coupling module 202 includes a capacitor C3. One end of the capacitor C3 is used to receive the positively attenuated differential signal PB, and the other end of the capacitor C3 is used to output the AC component PC of the positively attenuated differential signal. The capacitor C3 can pass AC and block DC, therefore, the AC component of the attenuated differential signal can be extracted.

[0067] Please refer to Figure 5In some embodiments, the impedance transformation module 203 includes: a switch Q1, resistors R5, R6, R7, and R8. One end of resistor R5 and one end of resistor R8 are used to receive the input signal (the AC portion PC of the attenuated differential signal in the positive direction). The other end of resistor R8 is connected to a voltage source V1, and the other end of resistor R5 is connected to the control terminal of switch Q1. The first terminal of switch Q1 is connected to the voltage supply terminal VCC through resistor R6, and the second terminal of switch Q1 is connected to the voltage supply terminal VEE through resistor R7. The second terminal of switch Q1 is used to output the signal PD. Switch Q1 can be a transistor with the first terminal being the collector, the second terminal being the emitter, and the control terminal being the base. Voltage source V1 determines the base voltage of switch Q1, and resistor R7 determines the quiescent current of the collector of switch Q1. The quiescent current of the collector is Iq1c = (V1 - VBE - VEE) / R7. This circuit is based on a common-collector structure and has a very small output impedance.

[0068] Please refer to Figure 6 In other embodiments, the impedance transformation module 203 includes: a switch Q1, a switch Q2, resistors R5, R7, R8, R9, R10, and R11. One end of resistor R5 and one end of resistor R8 are used to receive the input signal (the AC portion PC in the attenuated differential signal). The other end of resistor R8 is connected to a voltage source V1. The other end of resistor R5 is connected to the control terminal of switch Q1. The first terminal of switch Q1 is connected to the voltage supply terminal VCC through resistor R6. The second terminal of switch Q1 is connected to the voltage supply terminal VEE through resistor R7. The second terminal of switch Q1 is connected to one end of resistor R9. The other end of resistor R9 is connected to the control terminal of switch Q2. The first terminal of switch Q2 is connected to the voltage supply terminal VCC through resistor R10. The second terminal of switch Q2 is connected to the voltage supply terminal VEE through resistor R11. The second terminal of switch Q2 is used to output the signal PD. This circuit is a two-stage common-collector circuit. Since the output impedance and input impedance of the common-collector circuit are positively correlated, adding another stage of the common-collector circuit further reduces the output impedance.

[0069] Please refer to Figure 7 In some embodiments, the low-frequency amplification module 102 includes an attenuation unit 601, a first operational amplification unit 602, and a second operational amplification unit 603, wherein:

[0070] The attenuation unit 601 is used to attenuate the received two differential input signals.

[0071] The first operational amplifier unit 602 has a first input terminal and a second input terminal, which are connected to the output terminal of the attenuation unit 601. The first operational amplifier unit 602 performs differential-to-single-ended conversion and impedance transformation on the low-frequency signals acquired at its first input terminal and its second input terminal to output a low-frequency signal. In one embodiment, the first operational amplifier unit 602 is built using low-frequency devices, which can only process low-frequency signals and block high-frequency signals from passing through.

[0072] The second operational amplifier unit 603 is connected to the output terminal of the first operational amplifier unit 602. The second operational amplifier unit is used to perform first gain amplification on a low-frequency signal according to the amplification factor corresponding to the gain amplification control signal, so as to output a low-frequency signal after gain amplification.

[0073] In some embodiments, the attenuation unit includes resistors R12, R13, R14, and R15. One end of resistor R12 receives a differential input signal PA (positive differential input signal), and the other end of resistor R12 is connected to one end of resistor R13. The other end of resistor R13 is connected to ground, and the connected end of resistors R12 and R13 is used to output the attenuated differential input signal. One end of resistor R14 receives another differential input signal NA (negative differential input signal), and the other end of resistor R14 is connected to one end of resistor R15. The other end of resistor R15 is used to output the attenuated differential input signal. The positive differential input signal PA is attenuated by resistors R12 and R13, and the negative differential input signal NA is attenuated by resistors R14, R15, R16, and R17. These resistors satisfy the following relationship:

[0074] R12 = R14;

[0075] R13 = R16;

[0076] R12 / R13=(R14+R15) / (R16+R17);

[0077] Resistors R16 and R17 are added to the attenuation path of the negative phase differential input signal to make the input impedances of the positive and negative input terminals of the differential probe equal, wherein:

[0078] The input resistance at the positive input terminal is RINP = (R1 + R3) || (R12 + R13)

[0079] The input resistance at the negative input terminal is RINN = (R1 + R3) || (R14 + R15)

[0080] Since R12 and R14 are equal, the input resistances of the positive and negative input terminals will be equal when R15 = R13.

[0081] In some embodiments, the first operational amplifier unit includes an operational amplifier U1, resistors R16 and R17. The positive input terminal of operational amplifier U1 is used to acquire one differential input signal, and the negative input terminal of operational amplifier U1 is used to acquire another differential input signal. Resistors R16 and R17 are connected in series between the output terminal and the negative input terminal of operational amplifier U1. The output terminal of operational amplifier U1 is used to output a low-frequency signal. In one embodiment, operational amplifier U1 is a low-frequency device, which can only perform differential-to-single-ended conversion on low-frequency signals in the differential input signal, and cannot pass high-frequency signals.

[0082] The second operational amplifier unit includes operational amplifier U2, resistors R18, R19, R20, and R21, and switch S3. One end of resistor R18 is connected to the first terminal of switch S3. The end of resistor R18 connected to switch S3 is used to receive a low-frequency signal. The other end of resistor R18 is connected to the negative input terminal of operational amplifier U2. The second terminal of switch S3 is connected to one end of resistor R20. The other end of resistor R20 is connected to the negative input terminal of operational amplifier U2. Resistor R19 is connected between the negative input terminal and the output terminal of operational amplifier U2. The positive input terminal of operational amplifier U2 is connected to ground. The output terminal of operational amplifier U2 is connected to one end of resistor R21. The other end of resistor R21 is used to output a low-frequency signal after gain amplification. Switch S3 has a control terminal, which is used to control the first and second terminals of switch S3 to close or open in response to the gain amplification control signal CON.

[0083] The signal output from operational amplifier U1 is amplified by operational amplifier U2 before being applied to impedance transformation module 203. When switch S3 is open, the amplification factor is R19 / R18, which is the high attenuation state of the differential probe; when S3 is closed, the amplification factor is R19 / (R18||R20), which is the low attenuation state of the differential probe. The switching state of switch S3 is controlled by the gain amplification control signal CON. In one embodiment, switch S3 can be a MAX4649.

[0084] It should be noted that since the AC coupling module 202 in the signal processing link 101 is a capacitor, DC or extremely low frequency signals cannot pass through the capacitor. Therefore, the output of the low frequency amplification module 102 needs to be connected to the AC coupling module 202, that is, the output of the low frequency amplification module 102 needs to be connected to the input of the impedance transformation module 203.

[0085] Please refer to Figure 8 In some embodiments, the high-frequency amplification module 103 includes: a first amplifier 701, a second amplifier 702, and a high-frequency gain control unit 703, wherein:

[0086] The first amplifier 701 is connected to a signal processing link 101. The first amplifier 701 is used to perform a second gain amplification on the high-frequency signal output by the signal processing link connected to it, so as to output a high-frequency signal after gain amplification.

[0087] The second amplifier 702 is connected to another signal processing link 101. The second amplifier 702 is used to perform a second gain amplification on the high-frequency signal output from the connected signal processing link, so as to output another high-frequency signal with amplified gain.

[0088] The high-frequency gain control unit 703 is connected to the first amplifier 701 and the second amplifier 702. The high-frequency gain control unit 703 is used to adjust the amplification factor of the first amplifier 701 and the second amplifier 702 for second gain amplification based on the gain amplification control signal.

[0089] Please refer to Figure 9 and Figure 10 In some embodiments, the first amplifier 701 includes a switch Q3, a switch Q5, a resistor R22, a resistor R24, and a constant current source I1. One end of the resistor R22 is connected to a positive signal PD output from a signal processing link, and the other end of the resistor R22 is connected to the second terminal of the switch Q3. The control terminal of the switch Q3 is connected to a voltage source V2. The first terminal of the switch Q3 is connected to the control terminal of the switch Q5 and one end of the resistor R24. The other end of the resistor R24 ​​is connected to the voltage supply terminal VCC. The first terminal of the switch Q5 is connected to the voltage supply terminal VCC. The second terminal of the switch Q5 is connected to the voltage supply terminal VEE through the constant current source I1. The second terminal of the switch Q5 is used to output a positive high-frequency signal PE.

[0090] The second amplifier 702 includes switching transistors Q4 and Q6, resistors R23 and R25, and a constant current source I2. One end of resistor R23 is used to connect to the negative signal ND output from another signal processing link, and the other end of resistor R23 is connected to the second terminal of switching transistor Q4. The control terminal of switching transistor Q4 is connected to a voltage source V2. The first terminal of switching transistor Q4 is connected to the control terminal of switching transistor Q6 and one end of resistor R25. The other end of resistor R25 is connected to the voltage supply terminal VCC. The first terminal of switching transistor Q6 is connected to the voltage supply terminal VCC. The second terminal of switching transistor Q6 is connected to the voltage supply terminal VEE through the constant current source I2. The second terminal of switching transistor Q6 is used to output a negative high-frequency signal ND.

[0091] The high-frequency gain control unit 703 includes diodes D1 and D2, resistors R26, R27, R28, and R29, capacitor C4, and switching transistor Q7. One end of resistor R26 is connected to the first amplifier, and the other end of resistor R26 is connected to the cathode of diode D1. The anode of diode D1 is connected to the anode of diode D2. The cathode of diode D2 is connected to one end of resistor R27, and the other end of resistor R27 is connected to the second amplifier. The anodes of diodes D1 and D2 are connected to one end of capacitor C4 and the second terminal of switching transistor Q7. The other end of capacitor C4 is connected to ground. The first terminal of switching transistor Q7 is connected to the voltage supply terminal VCC through resistor R29. The control terminal of switching transistor Q7 receives the gain amplification control signal CON through resistor R28.

[0092] In the circuit described above, switching transistors Q3 and Q4 operate in a common-base amplifier configuration. When there is no current in the ICT circuit, diodes D1 and D2 are cut off, resulting in a gain of R24 / R22. The gain of the other path is R25 / R23, both equal. When there is current in the ICT circuit, diodes D1 and D2 conduct. Because capacitor C4 is present, for high-frequency signals, resistors R16 and R24, and R27 and R25 are connected in parallel. In this case, the high-frequency gain is (R24||R26) / R22 and (R25||R27) / R23. Voltage source V2 provides the quiescent operating point for switching transistors Q3 and Q4. Switches Q5 and Q6 operate in a common-collector configuration, serving as impedance transformers.

[0093] In some embodiments, the gain amplification control signal CON can be generated by the controller in the differential probe and output to the low-frequency amplification module 102 and the high-frequency amplification module 103, or it can be a control signal input from outside the differential probe.

[0094] Please refer to Figure 11 In some embodiments, the differential-to-single-ended module 104 includes a fully differential amplifier U3, resistors R31, R32, R33, R34, and R35. The negative input terminal of the fully differential amplifier U3 receives a positive signal PE output from the high-frequency amplification module 103 through resistor R33, and the positive input terminal of the fully differential amplifier U3 receives a negative signal NE output from the high-frequency amplification module 103 through resistor R32. Resistor R31 is connected between the negative input terminal and the positive output terminal of the fully differential amplifier U3, and resistor R30 is connected between the positive input terminal and the negative output terminal of the fully differential amplifier U3. The positive output terminal of the fully differential amplifier U3 is also connected to ground through resistor R35, and the negative output terminal of the fully differential amplifier U3 outputs a single-ended output signal VOUT through resistor R34.

[0095] In the circuit of the differential-to-single-ended module 104 described above, the amplification factor of one signal is R30 / R32, and R32 = R33, R30 = R31. The amplification factors of the positive and negative signals are equal, both being R30 / R32. Since the fully differential amplifier U3 is only used for output at one output terminal, the amplification factor is R30 / R32 / 2. In one implementation, the load resistor R35 connected to the output terminal of the fully differential amplifier U3 is generally 50 ohms. Therefore, the amplification factor is divided by 2, that is, the final amplification factor of the differential-to-single-ended module 104 should be R30 / R32 / 4.

[0096] The above-described specific examples are for illustrative purposes only and are not intended to limit the scope of this invention. Those skilled in the art to which this invention pertains can make various simple deductions, modifications, or substitutions based on the concept of this invention.

Claims

1. A differential probe, characterized in that, include: Two signal processing links, a low-frequency amplification module, a high-frequency amplification module, and a differential-to-single-ended converter module; Each of the signal processing links is used to receive one differential input signal and process the received differential input signal, the processing including at least signal attenuation processing, AC coupling processing and impedance transformation processing; The output of the low-frequency amplification module is connected to either of the two signal processing links; the low-frequency amplification module receives two differential input signals and, in response to a gain amplification control signal, performs a first gain amplification on the low-frequency signal of the two differential input signals, outputting a single low-frequency signal after gain amplification, wherein the amplification factor of the first gain amplification is associated with the gain amplification control signal; the single low-frequency signal after gain amplification is transmitted to the high-frequency amplification module by at least a portion of a signal processing link connected to the low-frequency amplification module; the low-frequency signal is a signal with a frequency lower than a first frequency; The input terminal of the high-frequency amplification module is connected to the two signal processing links, and the output terminal of the high-frequency amplification module is connected to the input terminal of the differential-to-single-ended module. The high-frequency amplification module, in response to the gain amplification control signal, performs a second gain amplification on the high-frequency signals of the two signals output from the two signal processing links, and outputs the two amplified high-frequency signals to the differential-to-single-ended module. The amplification factor of the second gain amplification is related to the gain amplification control signal. The high-frequency signal is a signal with a frequency greater than a second frequency, where the second frequency is greater than or equal to the first frequency. The differential-to-single-ended module is used to perform differential-to-single-ended processing on the two signals output from the two signal processing links respectively, and output a single-ended output signal.

2. The differential probe as described in claim 1, characterized in that, The low-frequency amplification module includes an attenuation unit, a first operational amplification unit, and a second operational amplification unit; The attenuation unit is used to attenuate the received two differential input signals; The first operational amplifier unit has a first input terminal and a second input terminal. The first input terminal and the second input terminal are connected to the output terminal of the attenuation unit. The first operational amplifier unit is used to perform differential-to-single-ended conversion and impedance transformation processing on the low-frequency signal acquired by its first input terminal and the low-frequency signal acquired by its second input terminal, so as to output a low-frequency signal. The second operational amplifier unit is connected to the output terminal of the first operational amplifier unit. The second operational amplifier unit is used to perform a first gain amplification on the low-frequency signal according to the amplification factor corresponding to the gain amplification control signal, so as to output a low-frequency signal after gain amplification.

3. The differential probe as described in claim 2, characterized in that, The attenuation unit includes resistors R12, R13, R14, and R15. One end of resistor R12 receives one differential input signal, and the other end of resistor R12 is connected to one end of resistor R13. The other end of resistor R13 is connected to ground, and the connected end of resistors R12 and R13 outputs the attenuated differential input signal. One end of resistor R14 receives another differential input signal, and the other end of resistor R14 is connected to one end of resistor R15. The other end of resistor R15 outputs the attenuated differential input signal; and / or, The first operational amplifier unit includes an operational amplifier U1, a resistor R16 and a resistor R17. The positive input terminal of the operational amplifier U1 is used to acquire one differential input signal, and the negative input terminal of the operational amplifier U1 is used to acquire another differential input signal. The output terminal and the negative input terminal of the operational amplifier U1 are connected in series with the resistor R16 and the resistor R17. The output terminal of the operational amplifier U1 is used to output a low-frequency signal. The second operational amplifier unit includes an operational amplifier U2, resistors R18, R19, R20, and R21, and a switch S3. One end of resistor R18 is connected to the first terminal of switch S3. The end of resistor R18 connected to switch S3 is used to receive a low-frequency signal. The other end of resistor R18 is connected to the negative input terminal of operational amplifier U2. The second terminal of switch S3 is connected to one end of resistor R20. The other end of resistor R20 is connected to the negative input terminal of operational amplifier U2. Resistor R19 is connected between the negative input terminal and the output terminal of operational amplifier U2. The positive input terminal of operational amplifier U2 is connected to ground. The output terminal of operational amplifier U2 is connected to one end of resistor R21. The other end of resistor R21 is used to output a low-frequency signal after gain amplification. Switch S3 has a control terminal, which is used to control the first and second terminals of switch S3 to close or open in response to the gain amplification control signal.

4. The differential probe as described in claim 1, characterized in that, The high-frequency amplification module includes: a first amplifier, a second amplifier, and a high-frequency gain control unit; The first amplifier is connected to a signal processing link, and the first amplifier is used to perform a second gain amplification on the high-frequency signal output by the signal processing link connected to it, so as to output a high-frequency signal after gain amplification. The second amplifier is connected to another signal processing link. The second amplifier is used to perform a second gain amplification on the high-frequency signal output by the signal processing link connected to it, so as to output another high-frequency signal after gain amplification. The high-frequency gain control unit is connected to the first amplifier and the second amplifier. The high-frequency gain control unit is used to adjust the amplification factor of the first amplifier and the second amplifier for second gain amplification based on the gain amplification control signal.

5. The differential probe as described in claim 4, characterized in that, The first amplifier includes switching transistors Q3 and Q5, resistors R22 and R24, and a constant current source I1. One end of resistor R22 is connected to a signal processing link, and the other end of resistor R22 is connected to the second terminal of switching transistor Q3. The control terminal of switching transistor Q3 is connected to a voltage source V2. The first terminal of switching transistor Q3 is connected to the control terminal of switching transistor Q5 and one end of resistor R24. The other end of resistor R24 ​​is connected to the voltage supply terminal VCC. The first terminal of switching transistor Q5 is connected to the voltage supply terminal VCC through the constant current source I1. The second terminal of switching transistor Q5 is used to output a high-frequency signal; and / or, The second amplifier includes switching transistors Q4 and Q6, resistors R23 and R25, and a constant current source I2. One end of resistor R23 is connected to another signal processing link, and the other end of resistor R23 is connected to the second terminal of switching transistor Q4. The control terminal of switching transistor Q4 is connected to a voltage source V2. The first terminal of switching transistor Q4 is connected to the control terminal of switching transistor Q6 and one end of resistor R25. The other end of resistor R25 is connected to the voltage supply terminal VCC. The first terminal of switching transistor Q6 is connected to the voltage supply terminal VCC. The second terminal of switching transistor Q6 is connected to the voltage supply terminal VEE through the constant current source I2. The second terminal of switching transistor Q6 is used to output a high-frequency signal; and / or, The high-frequency gain control unit includes diodes D1 and D2, resistors R26, R27, R28, and R29, capacitor C4, and switching transistor Q7. One end of resistor R26 is connected to the first amplifier, and the other end of resistor R26 is connected to the cathode of diode D1. The anode of diode D1 is connected to the anode of diode D2. The cathode of diode D2 is connected to one end of resistor R27, and the other end of resistor R27 is connected to the second amplifier. The anodes of diodes D1 and D2 are connected to one end of capacitor C4 and the second terminal of switching transistor Q7. The other end of capacitor C4 is connected to ground. The first terminal of switching transistor Q7 is connected to the voltage supply terminal VCC through resistor R29, and the control terminal of switching transistor Q7 receives the gain amplification control signal through resistor R28.

6. The differential probe as described in any one of claims 1 to 5, characterized in that, Each of the signal processing links includes: an attenuation module, an AC coupling module, and an impedance transformation module; The attenuation module is used to attenuate the received differential input signal and output the attenuated differential signal. The AC coupling module is connected between the output of the attenuation module and the input of the impedance transformation module; the AC coupling module is used to extract and output the AC component of the attenuated differential signal to the impedance transformation module. The impedance transformation module is used to provide the output impedance within a preset range and transmit the AC component of the received attenuated differential signal to the high-frequency amplification module.

7. The differential probe as described in claim 6, characterized in that, The output of the low-frequency amplification module is connected to the input of the impedance transformation module in either of the two signal processing links. The impedance transformation module is also used to transmit one low-frequency signal output by the low-frequency amplification module to the high-frequency amplification module.

8. The differential probe as described in claim 6, characterized in that, The attenuation module includes resistors R1, R2, R3, and R4, and capacitors C1 and C2. One end of resistor R1 receives a differential input signal, and the other end of resistor R1 is connected to one end of resistor R3 and one end of capacitor C2. The other end of resistor R3 is connected to ground, and the other end of capacitor C2 is connected to ground through resistor R4. One end of capacitor C1 is connected to one end of resistor R1, and the other end of capacitor C1 is connected to one end of resistor R2. The other end of resistor R2 is connected to the other end of resistor R1. The end where resistors R1, R2, R3, and capacitor C2 are connected is used to output the attenuated differential signal; and / or... The AC coupling module includes a capacitor C3. One end of the capacitor C3 is used to receive the attenuated differential signal, and the other end of the capacitor C3 is used to output the AC component of the attenuated differential signal.

9. The differential probe as described in claim 6, characterized in that, The impedance transformation module includes: a switch Q1, resistors R5, R6, R7, and R8. One end of resistor R5 and one end of resistor R8 are used to receive the input signal. The other end of resistor R8 is connected to a voltage source V1. The other end of resistor R5 is connected to the control terminal of switch Q1. The first terminal of switch Q1 is connected to the voltage supply terminal VCC through resistor R6, and the second terminal of switch Q1 is connected to the voltage supply terminal VEE through resistor R7. The second terminal of switch Q1 is used to output the signal; or... The impedance transformation module includes: a switch Q1, a switch Q2, resistors R5, R7, R8, R9, R10, and R11. One end of resistor R5 and one end of resistor R8 are used to receive the input signal. The other end of resistor R8 is connected to a voltage source V1. The other end of resistor R5 is connected to the control terminal of switch Q1. The first terminal of switch Q1 is connected to the voltage supply terminal VCC through resistor R6. The second terminal of switch Q1 is connected to the voltage supply terminal VEE through resistor R7. The second terminal of switch Q1 is connected to one end of resistor R9. The other end of resistor R9 is connected to the control terminal of switch Q2. The first terminal of switch Q2 is connected to the voltage supply terminal VCC through resistor R10. The second terminal of switch Q2 is connected to the voltage supply terminal VEE through resistor R11. The second terminal of switch Q2 is used to output the signal.

10. The differential probe as described in claim 6, characterized in that, Also includes: The controller is used to generate the gain amplification control signal and output the gain amplification control signal to the low-frequency amplification module and the high-frequency amplification module.

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