Differential probe circuit

Abstract

According to the differential probe circuit, the amplification factor of a differential input signal is controlled and adjusted through a gain amplification control signal, a relay does not need to be used for adjusting the gear of the gain amplification factor, and a low-frequency-band signal and a high-frequency-band signal in the differential input signal are transmitted to a differential-to-single-ended amplification module through different paths, so that the amplification factor of the differential input signal is adjusted. Therefore, the differential-to-single-ended amplification module can perform gain amplification on full-band signals, and has a relatively high bandwidth.

Description

Technical Field

[0001] This application relates to the field of probe technology, specifically to a differential probe circuit. 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, a high-power device is 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 like relays typically have large packages, significant parasitic effects, and bandwidth limitations, resulting in generally low bandwidth for differential probes.

[0004] In summary, differential probes capable of measuring higher voltages all suffer from the difficulty of balancing high bandwidth and the size of impedance range switching circuits. Utility Model Content

[0005] This application provides a differential probe circuit capable of measuring higher voltages, featuring high bandwidth and eliminating the need for relays to switch impedance levels.

[0006] According to one aspect of this application, one embodiment provides a differential probe circuit, including: two signal processing links, a low-frequency signal amplification module, and a differential-to-single-ended amplification 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 signal amplification module is connected to either of the two signal processing links; the low-frequency signal amplification module receives two differential input signals, amplifies the low-frequency signal in the two differential input signals, and outputs a low-frequency signal after amplification; the low-frequency signal is transmitted to the differential-to-single-ended amplification module via at least a portion of the signal processing link connected to the low-frequency signal amplification module; the low-frequency signal is a signal with a frequency lower than a first frequency.

[0009] The input terminal of the differential-to-single-ended amplifier module is connected to the output terminals of the two signal processing links. The differential-to-single-ended amplifier module, in response to a gain amplification control signal, performs full-band gain amplification on the two signals output from the two signal processing links respectively, and performs differential-to-single-ended processing on the two amplified signals to output a single-ended output signal. The full-band refers to the frequency band of the two differential input signals. The amplification factor of the full-band gain amplification is related to the gain amplification control signal.

[0010] In one embodiment, the differential-to-single-ended amplifier module includes a gain amplification control unit and a differential-to-single-ended amplifier unit;

[0011] The input terminal of the gain amplification control unit is connected to the output terminal of the two signal processing links, and is used to adjust the amplification factor of the full-band gain amplification in response to a gain amplification control signal;

[0012] The input terminal of the differential-to-single-ended amplifier unit is connected to the output terminal of the gain amplification control unit, and is used to perform full-band gain amplification and differential-to-single-ended processing on the two signals after gain amplification, and output a single-ended output signal.

[0013] In one embodiment, the gain amplification control unit includes: diode D1, diode D2, resistor R12, resistor R13, resistor R16, resistor R17, capacitor C7, current source I1, and current source I2.

[0014] One end of resistor R12 is used to receive a signal output from a signal processing link, and the other end of resistor R12 is used to output a signal with increased gain. The other end of resistor R12 is connected to the cathode of diode D1 through resistor R16, and the anode of diode D1 is connected to ground through capacitor C7. One end of resistor R13 is used to receive a signal output from another signal processing link, and the other end of resistor R13 is used to output another signal with increased gain. The other end of resistor R13 is connected to the cathode of diode D2 through resistor R17, and the anode of diode D2 is connected to the anode of diode D1 and used to receive the gain amplification control signal. The other end of resistor R12 is also connected to the voltage supply terminal VEE through current source I1, and the other end of resistor R13 is also connected to the voltage supply terminal VEE through current source I2. Current sources I1 and I2 also receive a current control signal, which is used to control the output current of current sources I1 and I2; and / or,

[0015] The differential-to-single-ended amplifier unit includes a fully differential amplifier U2, resistors R22, R23, R14, R15, R20, and R21. The negative input terminal of the fully differential amplifier U2 receives a gain-amplified signal from the gain amplifier unit via resistor R23, and the positive input terminal of the fully differential amplifier U2 receives a gain-amplified signal from the gain amplifier unit via resistor R22. Resistor R14 is connected between the negative output terminal and the positive input terminal of the fully differential amplifier U2, and resistor R15 is connected between the negative input terminal and the positive output terminal of the fully differential amplifier U2. The negative output terminal of the fully differential amplifier U2 is also connected to ground via resistor R20, and the positive output terminal of the fully differential amplifier U2 outputs a single-ended output signal via resistor R21.

[0016] In one embodiment, the low-frequency signal amplification module includes an attenuation unit, a first operational amplification unit, and a second operational amplification unit;

[0017] The attenuation unit is used to attenuate the received two differential input signals;

[0018] 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 processing on the low-frequency signal acquired by its first input terminal and the low-frequency signal acquired by its second input terminal to output a low-frequency signal.

[0019] 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 amplify the gain of the low-frequency signal and output the amplified low-frequency signal.

[0020] In one embodiment, it further includes: a differential feedback module;

[0021] The input terminal of the differential feedback module is connected to the output terminals of the two signal processing links, and the output terminal of the differential feedback module is connected to the low-frequency signal amplification module. The differential feedback module is used to convert the two signals output from the two signal processing links into single-ended differential signals and then feed them back to the second operational amplifier unit. The single-ended differential signals are transmitted from the second operational amplifier unit to the two signal processing links to adjust the DC voltage output by the two signal processing links.

[0022] In one embodiment, the attenuation unit includes: resistors R3, R4, and R5. One end of resistor R3 is used to receive one differential input signal, and the other end of resistor R3 is connected to one end of resistor R4. The other end of resistor R4 is connected to ground, and the connected end of resistors R3 and R4 is used to output the attenuated differential input signal. One end of resistor R5 is used to receive another differential input signal, and the other end of resistor R5 is used to output the attenuated other differential input signal; and / or,

[0023] The first operational amplifier unit includes an operational amplifier U1 and a resistor R7. 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 resistor R7 is connected between the output terminal and the negative input terminal of the operational amplifier U1. The output terminal of the operational amplifier U1 is used to output a low-frequency signal; and / or,

[0024] The second operational amplifier unit includes operational amplifier U3, resistors R8, R28, R2, capacitors C1 and C2. One end of resistor R8 is used to receive a low-frequency signal, and the other end of resistor R8 is connected to the negative input terminal of operational amplifier U3. One end of resistor R28 is used to acquire the single-ended differential signal output by the differential feedback module, and the other end of resistor R28 is connected to the negative input terminal of operational amplifier U3. Capacitor C2 is connected between the output terminal and the negative input terminal of operational amplifier U3. The output terminal of operational amplifier U3 is connected to one end of capacitor C1 and one end of resistor R2. The other end of capacitor C1 is connected to ground. The other end of resistor R2 is used to output a low-frequency signal after gain amplification.

[0025] In one embodiment, the second operational amplifier unit further includes a resistor R18, and the negative input terminal of the operational amplifier U3 is also used to receive a bias signal through the resistor R18, the bias signal being used to adjust the output voltage of the operational amplifier U3.

[0026] In one embodiment, the signal processing link includes: an attenuation module, an AC coupling module, and an impedance transformation module;

[0027] The attenuation module is used to attenuate the received differential input signal and output the attenuated differential signal.

[0028] 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.

[0029] The impedance transformation module is used to provide the output impedance within a preset range and transmit the AC portion of the received attenuated differential signal to the differential-to-single-ended amplifier module.

[0030] In one embodiment, it further includes: an input common-mode feedback module;

[0031] The input common-mode feedback module is connected to the input terminal of the impedance transformation module; the input common-mode feedback module is used to provide the impedance transformation module with a preset DC input voltage.

[0032] In one embodiment, the input common-mode feedback module includes: an operational amplifier U4, resistors R24, R25, R26, and R27, a voltage source V1, and a capacitor C8. The negative input terminal of the operational amplifier U4 is connected to the output terminal of an AC coupling module in a signal processing link through resistor R24. The negative input terminal of the operational amplifier U4 is also connected to the output terminal of an AC coupling module in another signal processing link through resistor R25. The positive input terminal of the operational amplifier U4 is connected to the positive terminal of the voltage source V1, and the negative terminal of the voltage source V1 is connected to ground. The capacitor C8 is connected between the negative input terminal and the output terminal of the operational amplifier U4. The output terminal of the operational amplifier U4 is connected to the input terminal of an impedance transformation module in a signal processing link through resistor R26. The output terminal of the operational amplifier U4 is also connected to the input terminal of an impedance transformation module in another signal processing link through resistor R27.

[0033] According to the differential probe circuit of the above embodiment, the amplification factor of the differential input signal is controlled and adjusted by the gain amplification control signal, without the need to use a relay to adjust the gain amplification factor level. Furthermore, the low-frequency and high-frequency signals in the differential input signal are transmitted to the differential-to-single-ended amplifier module through different paths, enabling the differential-to-single-ended amplifier module to amplify the gain of the full-band signal and have a high bandwidth. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of an existing differential probe.

[0035] Figure 2 This is a schematic diagram of the differential probe circuit provided in an embodiment of this application;

[0036] Figure 3 This is a schematic diagram of the signal processing link structure according to one embodiment;

[0037] Figure 4 This is a circuit diagram of an attenuation module according to one embodiment;

[0038] Figure 5 This is a circuit diagram of an impedance transformation module according to one embodiment;

[0039] Figure 6 This is a circuit diagram of a low-frequency signal amplification module according to one embodiment;

[0040] Figure 7 This is a circuit diagram of a low-frequency signal amplification module according to another embodiment;

[0041] Figure 8 This is a circuit diagram of a differential feedback module according to one embodiment;

[0042] Figure 9 This is a circuit diagram of a differential-to-single-ended amplifier module according to one embodiment;

[0043] Figure 10 This is a schematic diagram of the differential probe circuit in another embodiment;

[0044] Figure 11 This is a circuit diagram of an input common-mode feedback module according to one embodiment. Detailed Implementation

[0045] 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.

[0046] 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.

[0047] 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).

[0048] This application provides a differential probe circuit for use in measuring equipment such as oscilloscopes. Taking an oscilloscope as an example, the output terminal of the differential probe circuit is connected to the input channel of the oscilloscope via a coaxial cable, and the input terminal of the differential probe circuit is connected to the circuit under test via a coaxial cable to obtain two differential input signals.

[0049] Please refer to Figure 2 Some embodiments of the differential probe circuit include: two signal processing links 101, a low-frequency signal amplification module 102, and a differential-to-single-ended amplification module 103. 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 differential-to-single-ended amplification module 103, and the output terminal of the differential-to-single-ended amplification module 103 is connected to the measuring device via coaxial cables. The input terminal of the low-frequency signal amplification module 102 is connected to the input terminals of both signal processing links 101, and the output terminal of the low-frequency signal amplification module 102 is connected to any one of the two signal processing links 101. The various modules are described in detail below.

[0050] 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.

[0051] The low-frequency signal amplification module 102 receives two differential input signals, amplifies the low-frequency signal in the two differential input signals, and outputs a single amplified low-frequency signal. This amplified low-frequency signal is transmitted to the differential-to-single-ended amplification module 103 via at least a portion of a signal processing link connected to the low-frequency signal amplification module 102. The low-frequency signal is a signal with a frequency lower than a first frequency.

[0052] The differential-to-single-ended amplifier module 103 is used to respond to a gain amplification control signal to perform full-band gain amplification on the two signals output from the two signal processing links 101 respectively, and to perform differential-to-single-ended processing on the two amplified signals to output a single-ended output signal; wherein, the full-band refers to the frequency band corresponding to the two differential input signals; and the amplification factor of the full-band gain amplification is related to the gain amplification control signal.

[0053] With the differential probe circuit 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 transmitted separately to the differential-to-single-ended amplifier module for gain amplification, enabling the measurement of differential input signals with higher voltages and providing a higher bandwidth.

[0054] The following provides some specific circuit embodiments for each module in the differential probe circuit described above. It should be noted that the circuits of each module in the differential probe circuit provided in this application are not limited to the following embodiments.

[0055] 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 differential-to-single-ended amplifier module 103.

[0056] 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.

[0057] 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.

[0058] 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 differential-to-single-ended amplifier module 103. Since the 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 the differential-to-single-ended amplifier module 103. Therefore, it is necessary to add impedance transformation module 203 to reduce the output impedance of attenuation module 201 before connecting it to differential-to-single-ended amplifier module 103.

[0059] In some embodiments, since the AC coupling module 202 blocks low-frequency signals and only allows high-frequency signals, the low-frequency signal amplification module 102 is required to provide a path for low-frequency signals. The low-frequency signal amplification module 102 converts the low-frequency signals in the two differential input signals into single-ended signals and outputs them to the rear of the AC coupling module 202. That is, the output terminal of the low-frequency signal amplification module 102 is connected to the input terminal of the impedance transformation module 203 in a signal processing link 101.

[0060] Please refer to Figure 4 In some embodiments, the attenuation module 201 includes resistors R1 and R33, capacitors C3 and C5. One end of resistor R1 receives a differential input signal VINP, where VINP is a positive differential input signal. The other end of resistor R1 is connected to one end of resistor R33 and one end of capacitor C5. The other end of resistor R33 is connected to ground, and the other end of capacitor C5 is also connected to ground. Capacitor C3 is connected across resistor R1. The end where resistors R1, R33, C3, and C5 are connected is used to output the positive attenuated differential signal VP1. In the above circuit, resistors R1 and R33 form a basic resistor divider circuit to attenuate the voltage of the input differential signal, while capacitors C3 and C5 provide high-frequency compensation.

[0061] In some embodiments, the AC coupling module 202 includes a capacitor C9. One end of the capacitor C9 is used to receive the positively attenuated differential signal VP1, and the other end of the capacitor C9 is used to output the AC component of the positively attenuated differential signal. The capacitor C9 can pass AC while blocking DC, therefore, the AC component of the attenuated differential signal can be extracted.

[0062] Please refer to Figure 5 In some embodiments, the impedance transformation module 203 includes a switch Q1 and a resistor R10. The control terminal of the switch Q1 is used to receive the input signal (the AC component of the attenuated differential signal and the input signal VP2 composed of the output signal of the low-frequency signal amplification module 102). The first terminal of the switch Q1 is connected to the voltage supply terminal VCC, and the second terminal of the switch Q1 is connected to the voltage supply terminal VEE through the resistor R10. The second terminal of the switch Q1 is used to output a positive signal VOP, that is, a positive signal VOP output by a signal processing link 101. The 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. This circuit is based on a common-collector structure, resulting in a very low output impedance.

[0063] Please refer to Figure 6 In some embodiments, the low-frequency signal amplification module 102 includes an attenuation unit 601, a first operational amplification unit 602, and a second operational amplification unit 603, wherein:

[0064] The attenuation unit 601 is used to attenuate the received two differential input signals.

[0065] 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 is used to perform differential-to-single-ended conversion and impedance transformation on the low-frequency signal acquired at its first input terminal and the low-frequency signal acquired at its second input terminal to output a low-frequency signal. Specifically, the first input terminal is used to acquire the low-frequency signal in the positive differential input signal VINP, and the second input terminal is used to acquire the low-frequency signal in the negative differential input signal VINN. In one embodiment, the first operational amplifier unit 602 is a device for low-frequency signals; that is, the first operational amplifier unit 602 can only process the low-frequency signal in the differential input signal and blocks the passage of high-frequency signals.

[0066] 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 amplify the gain of a low-frequency signal and output the amplified low-frequency signal. The amplification factor of the second operational amplifier unit 603 is related to the resistance value of the resistor connected in series with it.

[0067] In some embodiments, since the VBE (base-emitter voltage) of the switching transistors in the impedance transformation modules 203 of the two signal processing links 101 are different, the DC voltage output by the two signal processing links 101 may be different. In order to eliminate the difference in the DC voltage output by the two signal processing links 101, this embodiment of the application also adds a differential feedback module 104. The input terminal of the differential feedback module 104 is connected to the output terminal of the two signal processing links 101, and the output terminal of the differential feedback module 104 is connected to the low frequency signal amplification module 102. The differential feedback module 104 is used to convert the two signals output by the two signal processing links 101 into single-ended differential signals and then feed them back to the second operational amplification unit 603. The single-ended differential signals are transmitted by the second operational amplification unit to the two signal processing links to adjust the DC voltage output by the two signal processing links.

[0068] In some embodiments, the attenuation unit 601 includes: resistors R3, R4, and R5. One end of resistor R3 is used to receive a differential input signal VINP, and the other end of resistor R3 is connected to one end of resistor R4. The other end of resistor R4 is connected to ground, and the end where resistors R3 and R4 are connected is used to output an attenuated differential input signal. One end of resistor R5 is used to receive another differential input signal VINN, and the other end of resistor R5 is used to output another attenuated differential input signal.

[0069] The first operational amplifier unit 602 includes an operational amplifier U1 and a resistor R7. 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 resistor R7 is connected between the output terminal and the negative input terminal of the operational amplifier U1, and the output terminal of the operational amplifier U1 is used to output a low-frequency signal. The attenuation ratio of the positive differential input signal VINP is R3 / R4, and the attenuation ratio of the negative differential input signal VINN is R5 / R7. In one embodiment, the operational amplifier U1 is a low-frequency device, capable only of performing differential-to-single-ended conversion on low-frequency signals; high-frequency signals cannot pass through the operational amplifier U1.

[0070] The second operational amplifier unit 603 includes an operational amplifier U3, resistors R8, R28, R2, capacitors C1 and C2. One end of resistor R8 is used to receive a low-frequency signal, and the other end of resistor R8 is connected to the negative input terminal of operational amplifier U3. One end of resistor R28 is used to obtain the single-ended differential signal output by differential feedback module 104, and the other end of resistor R28 is connected to the negative input terminal of operational amplifier U3. Capacitor C2 is connected between the output terminal and the negative input terminal of operational amplifier U3. The output terminal of operational amplifier U3 is connected to one end of capacitor C1 and one end of resistor R2. The other end of capacitor C1 is connected to ground. The other end of resistor R2 is used to output a low-frequency signal after gain amplification.

[0071] Please refer to Figure 7 In another embodiment, the second operational amplifier unit 603 further includes a resistor R18. The negative input terminal of the operational amplifier U3 is also used to receive a bias signal VOFFSET through the resistor R18. The bias signal VOFFSET, a low-frequency signal V2 after gain amplification, and the single-ended differential signal output by the differential feedback module 104 together constitute the negative input of the operational amplifier U3 to adjust the output gain of the operational amplifier U3.

[0072] Please refer to Figure 8 In some embodiments, the differential feedback module 104 includes an operational amplifier U5, resistors R29, R30, R31, and R32. The positive input terminal of the operational amplifier U5 receives an output signal VOP from a signal processing link 101 through resistor R29, and the negative input terminal of the operational amplifier U5 receives an output signal VON from another signal processing link 101 through resistor R31. The positive input terminal of the operational amplifier U5 is also connected to ground through resistor R30, and resistor R32 is connected between the negative input terminal and the output terminal of the operational amplifier U5. The output terminal of the operational amplifier U5 is used to output a single-ended differential signal to the second operational amplifier unit 603.

[0073] In summary, Figure 6 and Figure 8 In the circuit shown, the gain of the differential feedback module 104 is R32 / R31. The premise for satisfying this gain is R29 / (R30+R29)=R31 / (R32+R31). Therefore, the gain of the entire low-frequency path is (R7 / R5)*(R32 / R31)*(R28 / R8). In order to ensure that the gain of the probe is consistent throughout the entire frequency band, it should satisfy (R7 / R5)*(R32 / R31)*(R28 / R8)=R33 / (R1+R33)=R34 / (R9+R34).

[0074] exist Figure 7 and Figure 8 In the circuit shown, by adding resistor R18 and DC bias voltage VOFFSET, the DC bias of the input signal can be canceled, so that the probe has the function of DC bias. According to the superposition principle, the gain of bias signal VOFFSET is (R32 / R31)*(R28 / R18).

[0075] Please refer to Figure 9 In some embodiments, the differential-to-single-ended amplifier module 103 includes a gain amplification control unit 901 and a differential-to-single-ended amplifier unit 902. The input terminal of the gain amplification control unit 901 is connected to the output terminals of two signal processing links 101, and is used to adjust the amplification factor of the full-band gain amplification in response to a gain amplification control signal. The input terminal of the differential-to-single-ended amplifier unit 902 is connected to the output terminal of the gain amplification control unit 901, and is used to perform full-band gain amplification and differential-to-single-ended processing on the two signals after gain amplification, and output a single-ended output signal.

[0076] In some embodiments, the gain amplification control unit 901 includes: diode D1, diode D2, resistors R12, R13, R16, and R17, capacitor C7, current source I1, and current source I2; one end of resistor R12 is used to receive a signal output from a signal processing link 101, and the other end of resistor R12 is used to output a signal with amplified gain; the other end of resistor R12 is connected to the cathode of diode D1 through resistor R16, and the anode of diode D1 is connected to ground through capacitor C7; one end of resistor R13 is used to receive a signal output from another signal processing link, and resistor... The other end of resistor R13 is used to output another amplified signal. The other end of resistor R13 is connected to the cathode of diode D2 through resistor R17. The anode of diode D2 is connected to the anode of diode D1 and is used to receive the gain amplification control signals (VCT, ICT). The other end of resistor R12 is also connected to the voltage supply terminal VEE through current source I1, and the other end of resistor R13 is also connected to the voltage supply terminal VEE through current source I2. Current sources I1 and I2 also receive a current control signal, which is used to control the output current of current sources I1 and I2. The gain amplification control signals include a control voltage VCT and a control current ICT. Under the combined control of the control voltage VCT and the control current ICT, the amplification factor of the full-band gain amplification is adjusted.

[0077] In some embodiments, the differential-to-single-ended amplifier unit 902 includes a fully differential amplifier U2, resistors R22, R23, R14, R15, R20, and R21. The negative input terminal of the fully differential amplifier U2 receives a gain-amplified signal output by the gain amplifier unit through resistor R23, and the positive input terminal of the fully differential amplifier U2 receives a gain-amplified signal output by the gain amplifier unit through resistor R22. Resistor R14 is connected between the negative output terminal and the positive input terminal of the fully differential amplifier U2, and resistor R15 is connected between the negative input terminal and the positive output terminal of the fully differential amplifier U2. The negative output terminal of the fully differential amplifier U2 is also connected to ground through resistor R20, and the positive output terminal of the fully differential amplifier U2 outputs a single-ended output signal through resistor R21.

[0078] In the circuit described above, the resistors at the positive and negative input terminals of the fully differential amplifier U2 should be symmetrical, i.e., R12 = R13, R16 = R17, R22 = R23, and R14 = R15. The gain of the fully differential amplifier U2 is changed by controlling the conduction of diodes D1 and D2 through VCT. The following explains how the gain of the fully differential amplifier U2 is adjusted:

[0079] When VCT is a large negative voltage, this negative voltage is greater than the negative voltage of VOP\VON corresponding to the input signal in all input ranges of the fully differential amplifier U2. This ensures that diodes D1 and D2 will not conduct, and at the same time, the ICT-controlled programmable current sources I1 and I2 will not generate current. Therefore, the gain of the fully differential amplifier U2 is: VOUT / (VOP-VON)=0.5*R14 / (R12+R22).

[0080] When VCT is a large positive voltage, this positive voltage is greater than the positive voltages of VOP and VON corresponding to the input signals across all input ranges of the fully differential amplifier U2. Therefore, diodes D1 and D2 can be guaranteed to conduct, and with the ICT-controlled programmable current sources I1 and I2 generating current, the gain of the fully differential amplifier U2 is:

[0081] VOUT / (VOP-VON)=0.5*R14 / (R12+R22)*((R16+R17) / (R16+R17+R12)).

[0082] Among them, programmable current source I1 and programmable current source I2 provide current return paths when diodes D1 and D2 are turned on.

[0083] In some embodiments, to ensure that the input common-mode voltage of the differential-to-single-ended amplifier module 103 is as close to 0V as possible, since the fully differential amplifier U2 is powered by both positive and negative voltages, if the input common-mode voltage of the fully differential amplifier U2 is close to 0V, then the positive and negative ranges of the input signal are the same. Therefore, the static voltages of VOP and VON should be as close to 0V as possible. Furthermore, VP2 = VN2 = VBE, where VBE is the base-emitter voltage difference of the switching transistor in the impedance transformation module 203, typically 0.6 to 0.9V. VP2 and VN2 are the two input signals to the impedance transformation module 203. To ensure that VP2 and VN2 meet the above requirements, please refer to... Figure 10 In this embodiment, an input common-mode feedback module 105 is added. The input common-mode feedback module 105 is used to provide a DC input voltage with a preset voltage value to the impedance transformation module.

[0084] Please refer to Figure 11In some embodiments, the input common-mode feedback module 105 includes: an operational amplifier U4, resistors R24, R25, R26, and R27, a voltage source V1, and a capacitor C8. The negative input terminal of the operational amplifier U4 is connected to the output terminal of an AC coupling module 202 in a signal processing link 101 through resistor R24. The negative input terminal of the operational amplifier U4 is also connected to the output terminal of another AC coupling module 202 in a signal processing link 101 through resistor R25. The positive input terminal of the operational amplifier U4 is connected to the positive terminal of the voltage source V1, and the negative terminal of the voltage source V1 is connected to ground. The capacitor C8 is connected between the negative input terminal and the output terminal of the operational amplifier U4. The output terminal of the operational amplifier U4 is connected to the input terminal of an impedance transformation module in a signal processing link through resistor R26. The output terminal of the operational amplifier U4 is also connected to the input terminal of another impedance transformation module in a signal processing link through resistor R27. Thus, by adjusting the voltage of voltage source V1 to make V1 = VBE, VP2 = VN2 = VBE can be achieved, and then VOP = VON = 0V can be achieved. Here, VP2 and VN2 are the output signals of AC coupling modules 202 in the two signal processing links 101, VOP and VON are the output signals of impedance transformation modules 203 in the two signal processing links 101, and VBE is the voltage difference between the base and emitter of the switching transistor in the impedance transformation module 203.

[0085] 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 circuit, characterized in that, include: Two signal processing links, a low-frequency signal amplification module, and a differential-to-single-ended amplification 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 signal amplification module is connected to either of the two signal processing links; the low-frequency signal amplification module is used to receive two differential input signals, amplify the low-frequency signal in the two differential input signals, and output a low-frequency signal after amplification. The low-frequency signal is transmitted to the differential-to-single-ended amplifier module via at least a portion of a signal processing link connected to the low-frequency signal amplification module; the low-frequency signal is a signal with a frequency lower than the first frequency. The input terminal of the differential-to-single-ended amplifier module is connected to the output terminals of the two signal processing links. The differential-to-single-ended amplifier module, in response to a gain amplification control signal, performs full-band gain amplification on the two signals output from the two signal processing links respectively, and performs differential-to-single-ended processing on the two amplified signals to output a single-ended output signal. The full-band refers to the frequency band of the two differential input signals. The amplification factor of the full-band gain amplification is related to the gain amplification control signal.

2. The differential probe circuit as described in claim 1, characterized in that, The differential-to-single-ended amplifier module includes a gain amplification control unit and a differential-to-single-ended amplifier unit; The input terminal of the gain amplification control unit is connected to the output terminal of the two signal processing links, and is used to adjust the amplification factor of the full-band gain amplification in response to a gain amplification control signal; The input terminal of the differential-to-single-ended amplifier unit is connected to the output terminal of the gain amplification control unit, and is used to perform full-band gain amplification and differential-to-single-ended processing on the two signals after gain amplification, and output a single-ended output signal.

3. The differential probe circuit as described in claim 2, characterized in that, The gain amplification control unit includes: diode D1, diode D2, resistor R12, resistor R13, resistor R16, resistor R17, capacitor C7, current source I1, and current source I2; One end of resistor R12 is used to receive a signal output from a signal processing link, and the other end of resistor R12 is used to output a signal with increased gain. The other end of resistor R12 is connected to the cathode of diode D1 through resistor R16, and the anode of diode D1 is connected to ground through capacitor C7. One end of resistor R13 is used to receive a signal output from another signal processing link, and the other end of resistor R13 is used to output another signal with increased gain. The other end of resistor R13 is connected to the cathode of diode D2 through resistor R17, and the anode of diode D2 is connected to the anode of diode D1 and used to receive the gain amplification control signal. The other end of resistor R12 is also connected to the voltage supply terminal VEE through current source I1, and the other end of resistor R13 is also connected to the voltage supply terminal VEE through current source I2. Current sources I1 and I2 also receive a current control signal, which is used to control the output current of current sources I1 and I2; and / or, The differential-to-single-ended amplifier unit includes a fully differential amplifier U2, resistors R22, R23, R14, R15, R20, and R21. The negative input terminal of the fully differential amplifier U2 receives a gain-amplified signal from the gain amplifier unit via resistor R23, and the positive input terminal of the fully differential amplifier U2 receives a gain-amplified signal from the gain amplifier unit via resistor R22. Resistor R14 is connected between the negative output terminal and the positive input terminal of the fully differential amplifier U2, and resistor R15 is connected between the negative input terminal and the positive output terminal of the fully differential amplifier U2. The negative output terminal of the fully differential amplifier U2 is also connected to ground via resistor R20, and the positive output terminal of the fully differential amplifier U2 outputs a single-ended output signal via resistor R21.

4. The differential probe circuit as described in claim 1, characterized in that, The low-frequency signal 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 processing on the low-frequency signal acquired by its first input terminal and the low-frequency signal acquired by its second input terminal 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 amplify the gain of the low-frequency signal and output the amplified low-frequency signal.

5. The differential probe circuit as described in claim 4, characterized in that, Also includes: Differential mode feedback module; The input terminal of the differential feedback module is connected to the output terminals of the two signal processing links, and the output terminal of the differential feedback module is connected to the low-frequency signal amplification module. The differential feedback module is used to convert the two signals output from the two signal processing links into single-ended differential signals and then feed them back to the second operational amplifier unit. The single-ended differential signals are transmitted from the second operational amplifier unit to the two signal processing links to adjust the DC voltage output by the two signal processing links.

6. The differential probe circuit as described in claim 5, characterized in that, The attenuation unit includes resistors R3, R4, and R5. One end of resistor R3 receives one differential input signal, and the other end of resistor R3 is connected to one end of resistor R4. The other end of resistor R4 is connected to ground, and the connected end of resistors R3 and R4 outputs the attenuated differential input signal. One end of resistor R5 receives another differential input signal, and the other end of resistor R5 outputs the attenuated differential input signal; and / or, The first operational amplifier unit includes an operational amplifier U1 and a resistor R7. 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 resistor R7 is connected between the output terminal and the negative input terminal of the operational amplifier U1. The output terminal of the operational amplifier U1 is used to output a low-frequency signal; and / or, The second operational amplifier unit includes operational amplifier U3, resistors R8, R28, R2, capacitors C1 and C2. One end of resistor R8 is used to receive a low-frequency signal, and the other end of resistor R8 is connected to the negative input terminal of operational amplifier U3. One end of resistor R28 is used to acquire the single-ended differential signal output by the differential feedback module, and the other end of resistor R28 is connected to the negative input terminal of operational amplifier U3. Capacitor C2 is connected between the output terminal and the negative input terminal of operational amplifier U3. The output terminal of operational amplifier U3 is connected to one end of capacitor C1 and one end of resistor R2. The other end of capacitor C1 is connected to ground. The other end of resistor R2 is used to output a low-frequency signal after gain amplification.

7. The differential probe circuit as described in claim 6, characterized in that, The second operational amplifier unit also includes a resistor R18. The negative input terminal of the operational amplifier U3 is also used to receive a bias signal through the resistor R18. The bias signal is used to adjust the output voltage of the operational amplifier U3.

8. The differential probe circuit as described in claim 1, characterized in that, The signal processing link 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 portion of the received attenuated differential signal to the differential-to-single-ended amplifier module.

9. The differential probe circuit as described in claim 8, characterized in that, Also includes: Input common-mode feedback module; The input common-mode feedback module is connected to the input terminal of the impedance transformation module; the input common-mode feedback module is used to provide the impedance transformation module with a preset DC input voltage.

10. The differential probe circuit as described in claim 9, characterized in that, The input common-mode feedback module includes: operational amplifier U4, resistors R24, R25, R26, and R27, voltage source V1, and capacitor C8. The negative input terminal of operational amplifier U4 is connected to the output terminal of an AC coupling module in a signal processing link through resistor R24. The negative input terminal of operational amplifier U4 is also connected to the output terminal of an AC coupling module in another signal processing link through resistor R25. The positive input terminal of operational amplifier U4 is connected to the positive terminal of voltage source V1, and the negative terminal of voltage source V1 is connected to ground. Capacitor C8 is connected between the negative input terminal and the output terminal of operational amplifier U4. The output terminal of operational amplifier U4 is connected to the input terminal of an impedance transformation module in a signal processing link through resistor R26. The output terminal of operational amplifier U4 is also connected to the input terminal of an impedance transformation module in another signal processing link through resistor R27.

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