Signal amplification circuit and electronic equipment

Abstract

An embodiment of the present disclosure provides a signal amplification circuit and an electronic device, wherein the signal amplification circuit comprises: a first signal input terminal of a first operational amplifier is connected to one terminal of a first coupling circuit, and a first differential signal of a signal to be amplified is input to the other terminal of the first coupling circuit; a first signal input terminal of a second operational amplifier is connected to one terminal of a second coupling circuit, and a second differential signal of a signal to be amplified is input to the other terminal of the second coupling circuit; an output terminal of the second operational amplifier is respectively connected to a corresponding signal input terminal of a third operational amplifier; wherein the second signal input terminal of the first operational amplifier and the second signal input terminal of the second operational amplifier are respectively connected to a digital-to-analog converter via a voltage divider circuit; and an output terminal of the third operational amplifier is connected to the second signal input terminals of the first operational amplifier and the second operational amplifier via a third feedback network.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the field of signal detection technology, and in particular to a signal amplification circuit and an electronic device. Background Art

[0002] In many signal processing-related application scenarios, the signal to be processed needs to be coupled and amplified. For example, in a high-speed signal test scenario, the weak high-speed signal to be tested needs to be coupled and amplified before testing.

[0003] Active differential broadband amplifier circuits are widely used to achieve signal amplification due to their convenience and flexibility.

[0004] For the current active differential broadband amplifier circuit, it is necessary to expand the size of the input DC signal and dynamically adjust it, and it is also necessary to improve the performance such as the in-band gain flatness after amplification. Summary of the invention

[0005] Embodiments of the present disclosure provide a signal amplification circuit and an electronic device.

[0006] The embodiment of the present disclosure provides a signal amplification circuit, which includes: a first operational amplifier, a second operational amplifier, a third operational amplifier, a first coupling circuit, a second coupling circuit, a first feedback network, a second feedback network and a third feedback network; wherein the first signal input terminal of the first operational amplifier is connected to one terminal of the first coupling circuit, and the other terminal of the first coupling circuit inputs a first differential signal of a signal to be amplified; the output terminal of the first operational amplifier is connected to a signal input terminal of the first operational amplifier through a first feedback network; the first signal input terminal of the second operational amplifier is connected to one terminal of the second coupling circuit, and the other terminal of the second coupling circuit inputs a second differential signal of the signal to be amplified; the output terminal of the second operational amplifier is connected to a signal input terminal of the second operational amplifier through a second feedback network; the output terminal of the first operational amplifier and the output terminal of the second operational amplifier are respectively connected to the corresponding signal input terminal of the third operational amplifier; wherein the second signal input terminal of the first operational amplifier and the second signal input terminal of the second operational amplifier are respectively connected to a digital-to-analog converter through a voltage divider circuit; the output terminal of the third operational amplifier is connected to the second signal input terminal of the first operational amplifier and the second signal input terminal of the second operational amplifier through the third feedback network.

[0007] According to the above scheme, the first operational amplifier and the second operational amplifier form a first-stage signal amplification circuit, and the third operational amplifier forms a second-stage signal amplification circuit. The first signal input end of the first-stage signal amplification circuit inputs two differential signals; the second signal input end of the first operational amplifier inputs the DC power supply signal output by the first analog-to-digital converter, and the second signal input end of the second operational amplifier inputs the DC power supply signal output by the second digital-to-analog converter to offset or attenuate the DC signal in the differential input signal, thereby expanding the size of the DC signal that can be input. In addition, the DC signal is offset or attenuated by the first digital-to-analog converter and the second analog-to-digital converter, and the DC signal in the input signal is dynamically adjusted. In addition, the stability of the DC bias of the signal amplification circuit can be ensured by the first analog-to-digital converter and the second analog-to-digital converter by offsetting or attenuating the DC signal, so that the gain consistency of the DC and AC signals is better. In addition, through the third feedback network, the DC signal and the AC signal are fed back to the first-stage differential amplifier circuit to achieve the attenuation of the AC signal and the DC signal output by the third operational amplifier, which helps to achieve the consistency of the gain of the DC signal and the AC signal, and can improve the gain flatness in the broadband range including DC to AC signals.

[0008] In combination with the first aspect, in certain implementations of the first aspect, the first coupling circuit and the second coupling circuit respectively include: a DC signal coupling branch, and an AC signal coupling branch.

[0009] According to the above solution, the DC signal and the AC signal in the input differential signal are coupled to the first-stage differential operational amplifier through a coupling circuit including a DC coupling branch and an AC coupling branch.

[0010] In combination with the first aspect, in certain embodiments of the first aspect, the third feedback network is a resistance feedback network.

[0011] According to the above solution, the third feedback network can attenuate the gain of the low-frequency signal and the DC signal, which is conducive to achieving the flatness of the full-band gain.

[0012] In combination with the first aspect, in some implementations of the first aspect, a first AC coupling circuit and a second AC coupling circuit are further included; wherein,

[0013] One end of the first AC coupling circuit inputs the first differential signal, and the other end is connected to a signal input end of the third operational amplifier;

[0014] One end of the second AC coupling circuit inputs the second differential signal, and the other end is connected to another signal input end of the third operational amplifier; and

[0015] The output terminal of the first operational amplifier is connected to the second signal input terminal of the first operational amplifier through the first feedback network;

[0016] The output terminal of the second operational amplifier is connected to the second signal input terminal of the second operational amplifier through the second feedback network;

[0017] Among them, the first signal input terminal of the first operational amplifier and the first signal input terminal of the second operational amplifier are non-inverting input terminals; the second signal input terminal of the first operational amplifier and the second signal input terminal of the second operational amplifier are inverting input terminals.

[0018] According to the above scheme, by using the first AC coupling circuit and the second AC coupling circuit, the DC signal, the low-frequency signal and the high-frequency signal in the first differential signal and the second differential signal are separated, and the high-frequency signal is amplified by the third operational amplifier. The DC signal and the low-frequency signal in the differential signal are amplified by the first operational amplifier and the second operational amplifier and then enter the third operational amplifier for conditioning, so as to achieve the separation, attenuation and resynthesis of high and low frequency signals. By processing the high-frequency signal and the low-frequency signal separately, the bandwidth of the entire system can be effectively extended. The first-stage operational amplifier can be used to amplify the low-frequency signal, and the second-stage operational amplifier can process the high-frequency signal. Thus, the signal amplification circuit provided in this embodiment can amplify the signal within a wider frequency range. The high-frequency signal is coupled into the second-stage operational amplifier, which can reduce the influence of the high-frequency signal on the first-stage operational amplifier and enhance stability. By processing the full-band signal in a branch path, the gain of each frequency band can be better controlled and the possibility of oscillation can be reduced.

[0019] In combination with the first aspect, in certain embodiments of the first aspect, the impedance of the first coupling circuit matches the impedance of the first feedback network;

[0020] The impedance of the second coupling circuit matches the impedance of the second feedback network.

[0021] According to the above solution, by setting the impedance of the first feedback network and the impedance of the first coupling circuit to match, the differential signal input by the first operational amplifier can achieve a designed amplification factor.

[0022] In a second aspect, an embodiment of the present disclosure provides an electronic device, which includes: the signal amplification circuit as described in the first aspect.

[0023] The signal amplification circuit and electronic device provided by the present disclosure are composed of a first operational amplifier and a second operational amplifier to form a first-stage signal amplification circuit, and a third operational amplifier to form a second-stage signal amplification circuit. The first signal input end of the first-stage signal amplification circuit inputs two differential signals, and the differential signal is coupled to the output of the first-stage differential amplification circuit through a coupling circuit; the second signal input end of the first operational amplifier inputs a DC power supply signal output by the first analog-to-digital converter, and the second signal input end of the second operational amplifier inputs a DC power supply signal output by the second digital-to-analog converter to offset or attenuate the DC signal in the differential input signal, thereby expanding the size of the DC signal that can be input. In addition, the DC signal is offset or attenuated by the first digital-to-analog converter and the second analog-to-digital converter, thereby realizing dynamic adjustment of the DC signal in the input signal. In addition, the DC signal offset or attenuation by the first analog-to-digital converter and the second analog-to-digital converter can ensure the stability of the DC bias of the signal amplification circuit, thereby making the gain consistency of the DC and AC signals better. In addition, the DC signal and the AC signal are fed back to the first-stage differential amplifier circuit through the third feedback network to achieve attenuation of the AC signal and the DC signal output by the third operational amplifier, which helps to achieve consistency in the gains of the DC signal and the AC signal, and can improve the gain flatness in a wideband range including DC to AC signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic structure of the signal amplification circuit provided by the present disclosure Figure 1 ;

[0025] Figure 2 Schematic structure of the signal amplification circuit provided by the present disclosure Figure 2 ;

[0026] Figure 3 Schematic structure of the signal amplification circuit provided by the present disclosure Figure 3 ;

[0027] Figure 4 for Figure 2 The schematic diagram of the simulation result of the signal amplification circuit shown;

[0028] Figure 5 for Figure 3 The schematic diagram of the simulation result of the signal amplification circuit shown;

[0029] Figure 6 A schematic structural diagram of an electronic device provided by the present disclosure. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present disclosure will be described below in conjunction with the accompanying drawings in the embodiments of the present disclosure.

[0031] In application scenarios such as signal testing, it is necessary to amplify the coupled electrical signal. The electrical signal may include one or more of a direct current signal, a low-frequency alternating current signal, and a high-frequency alternating current signal.

[0032] In the related art, in order to effectively amplify the coupled electrical signal, the low-frequency signal and the high-frequency signal are separated, and then the separated high-frequency signal and the low-frequency signal are amplified respectively, and then the amplified low-frequency signal and the high-frequency signal are frequency synthesized. In the above-mentioned related art, the low-frequency signal and the high-frequency signal can be amplified, but the input DC signal cannot be offset and attenuated, so the size of the input DC signal is required to be relatively strict. In addition, since the high and low frequencies are separated and amplified respectively, the gain variation of the high and low frequencies is large, and the gain flatness in the entire band is poor.

[0033] The signal amplification circuit provided by the present invention has a first-stage operational amplifier, one input end of which inputs a differential signal of a signal to be amplified, and another signal input end is connected to a digitally controlled voltage source, and at the end, a low-frequency signal is fed back to the output end of the digitally controlled voltage source through a feedback network, so that a DC bias can be dynamically adjusted, a strong DC signal can be effectively offset, a DC signal can be accurately offset, and a real-time attenuation can be performed, so that the size of the DC signal that can be input can be expanded, and a broadband amplification function from DC to higher frequencies can be realized, as well as a gain-flattening amplification within the entire frequency band, thereby improving the flatness of the gain within the entire frequency band.

[0034] The signal amplification circuit provided by the present disclosure may be, for example, a differential signal low noise extraction circuit.

[0035] Please refer to Figure 1 , Figure 1 A schematic structure of a signal amplification circuit provided by the present disclosure Figure 1 ,like Figure 1 As shown, the signal amplification circuit includes:

[0036] A first operational amplifier 11 , a second operational amplifier 12 , a third operational amplifier 13 , a first coupling circuit 14 , a second coupling circuit 15 , a first feedback network 16 , a second feedback network 17 , and a third feedback network 18 .

[0037] The differential signal includes a first differential signal S+ and a second differential signal S- of the signal to be amplified.

[0038] In this embodiment, the first operational amplifier 11 and the second operational amplifier 12 constitute a first-stage differential signal amplifying circuit, and the third operational amplifier 13 constitutes a second-stage differential signal amplifying circuit.

[0039] like Figure 1As shown, the first operational amplifier 11 includes a first signal input terminal 111 and a second signal input terminal 112. The first signal input terminal 111 of the first operational amplifier 11 is connected to one end of the first coupling circuit 14, and the first differential signal S+ is input to the other end of the first coupling circuit 14 via a resistor R111. The resistance value of R111 can be equal to the transmission impedance of the signal to be amplified outside the signal amplification circuit, for example, 50 ohms.

[0040] The output terminal 113 of the first operational amplifier 11 is connected to a signal input terminal of the first operational amplifier 11 through the first feedback network 16. Figure 1 In the embodiment, the output terminal 113 of the first operational amplifier 11 is connected to the first signal input terminal 111 of the first operational amplifier 11 through the first feedback network 16 .

[0041] Similar to the first operational amplifier, the second operational amplifier 12 includes a first signal input terminal 121 and a second signal input terminal 122. The first signal input terminal 121 of the second operational amplifier 12 is connected to one end of the second coupling circuit 15. The second differential signal S- is input to the other end of the second coupling circuit 15 via the resistor R112. The resistance value of R112 can be equal to the transmission impedance of the signal to be amplified outside the signal amplification circuit, for example, 50 ohms.

[0042] The output terminal 123 of the second operational amplifier 12 is connected to a signal input terminal of the second operational amplifier 12 through the second feedback network 17. Figure 1 In the embodiment, the output terminal 123 of the second operational amplifier 12 is connected to the first signal input terminal 121 of the second operational amplifier 12 through the second feedback network 17 .

[0043] The output terminal 113 of the first operational amplifier 11 is connected to the inverting input terminal of the third operational amplifier 13 , and the output terminal 123 of the second operational amplifier 12 is connected to the non-inverting input terminal of the third operational amplifier 13 .

[0044] The second signal input terminal 112 of the first operational amplifier 11 is connected to the first analog-to-digital converter 191 through a voltage divider circuit, and the second signal input terminal 122 of the second operational amplifier 12 is connected to the second digital-to-analog converter 192 through a voltage divider circuit.

[0045] The first digital-to-analog converter 191 and the second analog-to-digital converter 192 may be a DC regulated power supply. The first digital-to-analog converter 191 and the second analog-to-digital converter 192 may be any adjustable digital-to-analog converter (DAC) capable of converting a digital power supply signal into an analog power supply signal, abbreviated as DAC, for example, a high-precision DAC. The high-precision DAC may output a DC signal with adjustable size, for example, a DC voltage signal with adjustable size.

[0046] Exemplarily, the voltage divider circuit corresponding to the first operational amplifier 11 includes a resistor R13 and a resistor R14.

[0047] Similar to the second signal input terminal 112 of the first operational amplifier 11, the second signal input terminal 122 of the second operational amplifier 12 is connected to the second digital-to-analog converter 192 through a voltage divider circuit. Exemplarily, the voltage divider circuit corresponding to the second operational amplifier 12 includes a resistor R18 and a resistor R19.

[0048] The output terminal of the third operational amplifier 13 is connected to the second signal input terminal 112 of the first operational amplifier 11 and to the second signal input terminal 122 of the second operational amplifier 12 through the third feedback network 18 .

[0049] Illustratively, the first differential signal S+ and the second differential signal S− may be voltage signals. For example, the first differential signal S+ may be a positive voltage signal, and the second differential signal S− may be a negative voltage signal.

[0050] The first operational amplifier 11 and the second operational amplifier 12 may be operational amplifiers with the same parameters. The above parameters may include, for example, one or more of the following: input offset voltage, input bias current, input impedance, output impedance, output current limit, open-loop gain, common mode rejection ratio, differential mode rejection ratio, bandwidth, operating voltage range, static power consumption, temperature drift, etc.

[0051] The first coupling circuit 14 can couple the first differential signal S+ to the first operational amplifier 11. The first differential signal S+ can include a DC signal and a low-frequency signal, or a DC signal, a low-frequency signal and a high-frequency signal. The first coupling circuit 14 can include a DC coupling circuit and an AC coupling circuit.

[0052] The second coupling circuit 15 can couple the second differential signal S- to the second operational amplifier 12. The second differential signal S- and the first differential signal S+ are the same type of signals, and can include a DC signal and a low-frequency signal, or a DC signal, a low-frequency signal and a high-frequency signal, respectively. The second coupling circuit 15 can include a DC coupling circuit and an AC coupling circuit.

[0053] In some implementations, the first feedback network 16 may be a local feedback corresponding to the first operational amplifier, and the impedance of the first feedback network 16 may match the impedance of the first coupling circuit 14. For example, the impedance of the first feedback network 16 and the impedance of the first coupling circuit 14 are respectively set according to the designed gain. By setting the impedance of the first feedback network 16 and the impedance of the first coupling circuit 14 to match, the first operational amplifier can achieve the designed gain for the input first differential signal S+.

[0054] The second feedback network 17 can be a local feedback corresponding to the second operational amplifier, and the impedance of the second feedback network 17 can match the impedance of the second coupling circuit 15, so as to realize the amplification function of the first-stage differential amplifier circuit on the second differential signal S-. By setting the impedance of the second feedback network 17 to match the impedance of the second coupling circuit 15, the second operational amplifier can achieve the designed amplification factor for the input second differential signal S-.

[0055] In the signal amplification circuit, the first differential signal S+ and the second differential signal S- can be mixed signals including a DC signal and a low-frequency signal, or mixed signals including a DC signal, a low-frequency signal and a high-frequency signal. Due to the presence of the DC signal, the DC signal will cause the DC operating voltage of the first operational amplifier 11 and the second operational amplifier 12 to increase, which may cause the first operational amplifier 11 and the second operational amplifier 12 to operate in a nonlinear state, thereby causing the signal amplification circuit to not work properly. Therefore, it is necessary to offset or attenuate the DC signal in the first differential signal S+ and the second differential signal S-. In order to achieve the offset or attenuation of the DC signal, in one embodiment, the first digital-to-analog converter 191 can provide an adjustable external DC signal to the second signal input terminal 112 of the first operational amplifier 11. The second digital-to-analog converter 192 can provide an adjustable external DC signal to the second signal input terminal 122 of the second operational amplifier 12. Exemplarily, the DC signal output by the first digital-to-analog converter 191 can offset or attenuate the DC signal in the first differential signal S+, for example, offset or attenuate the DC signal above the static operating point of the first operational amplifier 11 to keep the first operational amplifier operating at a stable static operating point.

[0056] The DC signal output by the second analog-to-digital converter 192 can offset or attenuate the DC signal in the second differential signal S-. For example, the DC signal above the static operating point of the second operational amplifier 12 can be offset or attenuated to keep the second operational amplifier 12 operating at a stable static operating point. As a result, the gain difference of different frequency signals through the above-mentioned signal amplification circuit is small, thereby improving the signal gain flatness in a wider frequency band.

[0057] The third feedback network 18 connects the output terminal of the third operational amplifier 13 with the signal input terminals of the first operational amplifier 11 and the second operational amplifier 12, thereby realizing cross-stage feedback. In some examples, the third feedback network 18 can use a resistor with a relatively large resistance value to realize cross-stage feedback of low-frequency signals and DC signals. It can be understood that when the third feedback network uses a resistor with a relatively large resistance value, only a small part of the high-frequency signal is cross-stage fed back, which can be ignored.

[0058] In this embodiment, the first operational amplifier 11 and the second operational amplifier 12 constitute a first-stage operational amplifier for amplifying an input signal.

[0059] In addition, since the second signal input terminal 112 of the first operational amplifier 11 is connected to the first digital-to-analog converter 191 through a resistor, the DC signal in the first differential signal S+ inputted by the first signal input terminal 111 of the first operational amplifier 11 can be offset or attenuated by the DC signal inputted by the second signal input terminal 112, and the DC signal inputted by the first signal input terminal 121 of the second operational amplifier 12 can be offset or attenuated by the DC signal inputted by the second signal input terminal 122. Since the DC signal in the first differential signal S+ can be offset and attenuated before being inputted into the first operational amplifier, the first operational amplifier can be in a linear working state.

[0060] Since the second signal input terminal 122 of the second operational amplifier 12 is connected to the second digital-to-analog converter 192 through a resistor, the DC signal in the second differential signal S- inputted from the first signal input terminal 121 of the second operational amplifier 12 can be offset or attenuated by the DC signal inputted from the second signal input terminal 122. After the DC signal in the second differential signal S- is offset and attenuated and then inputted to the second operational amplifier, the second operational amplifier 12 can be in a linear working state.

[0061] Therefore, a larger DC signal can be input into the first differential signal S+ and the second differential signal S-, thereby expanding the size of the DC signal that can be input into the signal amplification circuit. In addition, the DC signal can be dynamically adjusted by adjusting the DC signal output by the first digital-to-analog converter 191 and the second analog-to-digital converter 192 so that the first operational amplifier and the second operational amplifier are in a stable working state, thereby realizing the broadband amplification function of DC, low-frequency signals and high-frequency signals, and facilitating the improvement of the gain flatness of the full frequency band.

[0062] In one embodiment, a first resistor R11 is connected in series between the first coupling circuit 14 and the first signal input 111 of the first operational amplifier 11, and a second resistor R12 is connected in series between the output of the first operational amplifier 11 and the inverting input of the third operational amplifier 13; a third resistor R16 is connected in series between the second coupling circuit 15 and the first signal input 121 of the second operational amplifier 12, and a fourth resistor R17 is connected in series between the output of the second operational amplifier 12 and the non-inverting input of the third operational amplifier 13; wherein the resistance values ​​of the first resistor R11, the second resistor R12, the third resistor R16 and the fourth resistor R17 are equal, and the above resistance values ​​match the transmission impedance of the signal to be amplified outside the signal amplification circuit. For example, the resistance values ​​of the first resistor R11, the second resistor R12, the third resistor R16 and the fourth resistor R17 are equal to the transmission impedance outside the signal amplification circuit. The resistance values ​​of the first resistor R11, the second resistor R12, the third resistor R16 and the fourth resistor R17 are set to match the transmission impedance of the signal to be amplified outside the signal amplification circuit, which can prevent signal reflection and reduce the influence of the detected signal on the load effect.

[0063] In this embodiment, the first signal input end of the first operational amplifier inputs the first differential signal of the signal to be amplified through the first coupling circuit, the first signal input end of the second operational amplifier inputs the second differential signal of the signal to be amplified through the second coupling circuit, the output end of the first operational amplifier is connected to the input end of the first operational amplifier through the first feedback network to achieve the amplification of the first differential signal, and the output end of the second operational amplifier is connected to the input end of the second operational amplifier through the second feedback network to achieve the amplification of the second differential signal. The second signal input ends of the first operational amplifier and the second operational amplifier are respectively connected to the digital-to-analog converter, the DC signal inputted by the second signal input end can effectively offset or attenuate the DC signal inputted by the first signal input end, and the size of the DC signal that can be input can be expanded. In addition, the circuit enables the signal amplification circuit to operate at a relatively stable static operating point, which helps to improve the flatness of the gain of different frequency signals in a wide frequency band. The signal amplification circuit provided in this embodiment can achieve low-noise extraction of differential signals.

[0064] Please refer to Figure 2 , Figure 2 A schematic structure of a signal amplification circuit provided by the present disclosure Figure 2 . Figure 2 The signal amplification circuit provided in the embodiment shown is Figure 1Based on the illustrated embodiment, the first operational amplifier 11, the second operational amplifier 12, the third operational amplifier 13, the first coupling circuit 14, the second coupling circuit 15, the first feedback network 16, the second feedback network 17 and the third feedback network 18 provided by the present application are described. The contents already introduced in the aforementioned embodiment are not repeated here.

[0065] like Figure 2 In the embodiment, the first signal input terminal 111 of the first operational amplifier 11 is an inverting input terminal, and the second signal input terminal 112 is a non-inverting input terminal. The first feedback network 16 can constitute a negative feedback of the first operational amplifier.

[0066] The first signal input terminal 121 of the second operational amplifier 12 is an inverting input terminal, and the second signal input terminal 122 is a non-inverting input terminal. The second feedback network 17 constitutes negative feedback of the second operational amplifier.

[0067] In some embodiments, the first coupling circuit 14 includes a DC signal coupling branch and an AC signal coupling branch. The DC signal coupling branch includes a resistor R241, and the resistance of the resistor R241 can be designed to be relatively large, for example, 25 kilo-ohms. The AC signal coupling branch includes a first capacitor C241, and the size of the first capacitor can be set to between 100 and 1000 farads, for example, 300 farads, etc. The DC signal coupling branch can couple the DC signal in the first differential signal S+ to the first operational amplifier 11, and the AC signal coupling branch can couple the AC signal in the first differential signal S+ to the first operational amplifier 11.

[0068] The second coupling circuit 15 may include a DC signal coupling branch and an AC signal coupling branch. The DC signal coupling branch includes a resistor R251, and the AC signal coupling branch includes a capacitor C251. The resistance of the resistor R251 may be equal to the resistance of the resistor R241. The size of the capacitor C251 may be equal to the size of the capacitor C241. The DC signal coupling branch may couple the DC signal in the second differential signal S- to the second operational amplifier 12, and the AC signal coupling branch may couple the AC signal in the second differential signal S- to the second operational amplifier 12. The first feedback network 16 may include a resistor R261 and a capacitor C261, the size of the resistor R261 may be 10 ohms, and the size of the capacitor C261 may be 100 pF.

[0069] The design of the second feedback network 17 may be completely consistent with the design of the first feedback network 16 .

[0070] The first operational amplifier 11 , the first coupling circuit 14 , the first feedback network 16 , the second operational amplifier 12 , the second coupling circuit 15 , and the second feedback network 17 constitute a first-stage differential amplifier circuit.

[0071] It can be understood that the amplifier circuit composed of the first operational amplifier 11, resistors R111, R11, the first coupling circuit 14, the first feedback network 16, resistors R12, R13, R14 and the first digital-to-analog converter 191 is symmetrically structured with the amplifier circuit composed of the second operational amplifier 12, resistors R112, R16, the second feedback network 17, resistors R17, R18, R19 and the digital-to-analog converter.

[0072] The output terminal of the third operational amplifier 13 is connected to the second signal input terminal 112 of the first operational amplifier 11 through the third feedback network 18 , and is connected to the second signal input terminal 122 of the second operational amplifier 12 through the third feedback network 18 .

[0073] The second signal input terminal 112 of the first operational amplifier 11 is connected to the first analog-to-digital converter 191 through a voltage divider circuit.

[0074] The second signal input terminal 122 of the second operational amplifier 12 is connected to the second digital-to-analog converter 192 via a voltage divider circuit.

[0075] Exemplarily, the first operational amplifier 11 and the second operational amplifier 12 may be differential operational amplifiers. The magnitude of the output signal of the first operational amplifier 11 is related to the difference between the input signal at the in-phase terminal and the input signal at the inverting terminal of the first operational amplifier 11. The magnitude of the output signal of the second operational amplifier 12 is related to the difference between the input signal at the in-phase terminal and the input signal at the inverting terminal of the second operational amplifier.

[0076] The second signal input terminal 112 of the first operational amplifier 11 is connected to the first analog-to-digital converter 191, and the second signal input terminal 122 of the second operational amplifier 12 is connected to the second digital-to-analog converter 192. In addition, since the first operational amplifier 11 and the second operational amplifier 12 are both differential operational amplifier circuits, the first digital-to-analog converter 191 and the second analog-to-digital converter 192 can respectively offset the DC signals in the first differential signal S+ and the second differential signal S- input. On the one hand, the range of signals that can be conditioned by the signal amplification circuit can be increased. On the other hand, the above-mentioned offset can ensure the stability of the static operating point of the first operational amplifier and the second operational amplifier, so that the gain differences corresponding to multiple frequency points are small, which is conducive to ensuring the flatness of the gain within the broadband.

[0077] In some embodiments, the third feedback network may be a resistor feedback network, including a resistor R29, and the size of the resistor R29 may be 10 kilo-ohms. The third feedback network implements negative feedback of the signal amplification circuit. The third feedback network composed of the resistor R29 can implement feedback of the low-frequency signal and the DC signal output by the third operational amplifier to the second signal input terminal 112 of the first operational amplifier 11, and the second signal input terminal 122 of the second operational amplifier 12.

[0078] The resistance value of the third feedback network can affect the amplification factor of the entire amplifier circuit. For example, the amplification factor of the entire amplifier circuit is positively correlated with the resistance value of the third feedback network. The third feedback network can attenuate the gain of low-frequency signals and DC signals, which is conducive to achieving the flatness of the full-band gain.

[0079] In one example, the first operational amplifier 11 and the second operational amplifier 12 may be current mode differential amplifiers, and the inputs of the first operational amplifier 11 and the second operational amplifier 12 may be currents, and the outputs may be voltages. The first operational amplifier 11 and the second operational amplifier 12 may be mutual impedance amplifiers. The first differential signal S+ input to the inverting input terminal of the first operational amplifier 11 is coupled to the output of the first operational amplifier 11 through a resistor / capacitor element. The second differential signal S- input to the reverse input terminal of the second operational amplifier 12 is coupled to the output of the second operational amplifier 12 through a resistor or capacitor element. The AC coupling branch of the first feedback network 16 may isolate the DC signal through the low-frequency and high-frequency signals in the first differential signal S+. The DC signal in the first differential signal S+ may pass through the DC coupling branch of the first feedback network 16.

[0080] The first operational amplifier 11, the second operational amplifier 12 and related circuits such as the first feedback network 16, the second feedback network 17, the first coupling circuit 14 and the second coupling circuit 15 constitute the first stage differential operational amplifier, and the third operational amplifier 13 and related circuits such as the third feedback network 18, the second resistor R12 and the fourth circuit R17 constitute the second stage differential operational amplifier. The grounding at the in-phase input end of the first operational amplifier 11 is changed to the first digital-to-analog converter 191 (the digital-to-analog converter can be a high-precision DAC), and the grounding at the in-phase input end of the second operational amplifier 12 is changed to the second digital-to-analog converter 192. By adjusting the DC signal output by the first digital-to-analog converter 191 and the second analog-to-digital converter 192, the DC signal in the input first differential signal and the second differential signal is offset or attenuated. Thereby, the DC bias adjustment function is realized. When a large DC signal flows into the differential signal, the DC signal output by the first analog-to-digital converter 191 and the second analog-to-digital converter 192 is adjusted to offset or attenuate the DC signal input to the first operational amplifier and the second operational amplifier. The first differential signal after DC attenuation is input to the first operational amplifier, and the second differential signal after DC attenuation is input to the second operational amplifier, thereby completing the differential amplification function through the two-stage differential operational amplifier.

[0081] The signal amplification circuit can accurately offset or attenuate the DC signal. Thus, it supports a larger DC signal input. At the rear end of the third operational amplifier, the low-frequency signal and the DC signal are fed back to the output of the first analog-to-digital converter 191 and the second analog-to-digital converter through a resistor feedback network to dynamically adjust the DC bias value. Thus, a broadband amplification function from DC to higher frequencies (millimeter waves, etc.) can be achieved.

[0082] A resistor R11 is connected in series between the first coupling circuit 14 and the first signal input terminal 111 of the first operational amplifier 11. A resistor R16 is connected in series between the second coupling circuit 15 and the first signal input terminal 121 of the second operational amplifier 12. The resistors R11 and R16 may be resistors with relatively small resistances, such as 50 ohms. The resistors R11 and R16 may adjust the gain flatness.

[0083] Please refer to Figure 4 , Figure 4 for Figure 2 The simulation result diagram of the signal amplification circuit of the embodiment shown is as follows: Figure 4 As shown, the simulation results show that the circuit can extract differential signals from DC to 30GHz, with a gain flatness of ±2dB. From DC to 10MHz, the circuit presents a large input impedance, reaching about tens of kΩ. After 10MHz, the impedance drops sharply.

[0084] In this embodiment, the input differential signal (a differential signal composed of the first differential signal and the second differential signal) is coupled to the first-stage differential operational amplifier through a coupling circuit including a DC coupling branch and an AC coupling branch, and enters the second-stage differential operational amplifier through the first-stage differential operational amplifier. At the rear end of the second-stage differential amplifier, the low-frequency signal is simultaneously fed back to the output ends of the two analog-to-digital converters through a resistor feedback network, thereby dynamically adjusting the DC bias, which can achieve a broadband amplification function from DC to higher frequencies (millimeter waves, etc.), and is beneficial to improving the flatness of the gain corresponding to different frequencies within the above-mentioned broadband.

[0085] Please refer to Figure 3 , Figure 3 The structure of the signal amplification circuit provided by the present invention is shown in FIG. Figure 3 . Figure 3 The signal amplification circuit provided in the embodiment shown is Figure 1 Based on the embodiment shown, the first operational amplifier 31, the second operational amplifier 32, the third operational amplifier 33, the first coupling circuit 34, the second coupling circuit 35, the first feedback network 36, the second feedback network 37 and the third feedback network 38 are described. Figure 1 On the basis of the embodiment shown, a first AC coupling circuit 361 and a second AC coupling circuit 371 are added. The contents already introduced in the above embodiment are not repeated here. The first signal input terminal 311 of the first operational amplifier 31 is connected to one end of the first coupling circuit 34, and the other end of the first coupling circuit 34 inputs the first differential signal S+ through the resistor R311.

[0086] The first coupling circuit 34 includes a capacitor C341 and a resistor R341. The capacitor C341 has a value of 200 femtofarads, and the resistor R341 has a value of 25 kilohms.

[0087] The output terminal 313 of the first operational amplifier 31 is connected to the second signal input terminal 312 of the first operational amplifier 31 through the first feedback network 36. The first feedback network 36 includes resistors R39, R33 and capacitor C33. Among them, the size of the resistor R39 is 7.5 kiloohms, the size of the resistor R33 is 1 kiloohm, and the size of the capacitor C33 is 100 pF. The first signal input terminal 311 of the first operational amplifier 31 is a non-inverting input terminal, and the second signal input terminal 312 of the first operational amplifier 31 is an inverting input terminal. The output terminal 323 of the second operational amplifier 32 is connected to the inverting signal input terminal of the second signal input terminal 322 of the second operational amplifier 32 through the second feedback network 37. The second feedback network includes resistors R316, R37 and capacitor C34. The first signal input terminal 321 of the second operational amplifier 32 is a non-inverting input terminal, and the second signal input terminal 322 of the second operational amplifier 32 is an inverting input terminal.

[0088] The second signal input terminal 312 of the first operational amplifier 31 is connected to the first digital-to-analog converter 391 through a voltage divider circuit. The second signal input terminal 322 of the second operational amplifier 32 is connected to the second digital-to-analog converter 392 through a voltage divider circuit.

[0089] The output terminal of the third operational amplifier 33 is connected to the second signal input terminal 312 of the first operational amplifier 31 through the third feedback network 38, and is connected to the second signal input terminal 322 of the second operational amplifier 32. The third feedback network may include a resistor R319. The third feedback network constitutes inter-stage negative feedback. The first signal input terminal of the first operational amplifier 11 may be a non-inverting input terminal, and the second signal input terminal may be an inverting input terminal. The first signal input terminal of the second operational amplifier 12 may be a non-inverting input terminal, and the second signal input terminal may be an inverting input terminal.

[0090] A non-inverting input terminal 311 of the first operational amplifier 31 is connected to resistors R31 and R313 connected in series, wherein one end of the resistor R313 not connected to the resistor R31 is grounded.

[0091] The inverting input terminal 312 of the first operational amplifier 31 is connected to resistors R33 and R34 connected in series. The resistor R34 is grounded. The output terminal of the first digital-to-analog converter 391 is connected to the end of the resistor R33 that is not connected to the first operational amplifier 31 .

[0092] The non-inverting input terminal 321 of the second operational amplifier 32 is connected to the resistors R35 and R314 connected in series, wherein the end of the resistor R314 not connected to the resistor R35 is grounded.

[0093] The inverting input terminal 322 of the second operational amplifier 32 is connected to resistors R37 and R38 connected in series, wherein one end of the resistor R38 is grounded. The output end of the digital-to-analog converter is connected to the end of the resistor R37 that is not connected to the first operational amplifier.

[0094] It can be understood that the inter-stage amplifier circuit composed of the first operational amplifier 31, resistor R311, first coupling circuit 34, resistor R313, resistor R31, resistor R33, resistor R34, resistor R32, resistor R39, R310, capacitors C31, C33 is symmetrically structured with the inter-stage amplifier circuit composed of the second operational amplifier 32, resistor R312, second coupling circuit 35, resistor R314, resistor R35, resistor R37, resistor R38, resistor R36, resistor R316, resistor R317 and capacitors C32, C34.

[0095] This embodiment further includes a first AC coupling circuit 361 and a second AC coupling circuit 371. Figure 3As shown, one end of the first AC coupling circuit 361 inputs the first differential signal S+, and the other end is connected to the inverting signal input end of the third operational amplifier 33. One end of the second AC coupling circuit 371 inputs the second differential signal S-, and the other end is connected to the inverting signal input end of the third operational amplifier 33.

[0096] The first AC coupling circuit 361 may include a capacitor C31. The first AC coupling circuit 361 directly transmits the high-frequency signal in the first differential signal S+ to the second differential amplifier circuit (the third operational amplifier 33). The second AC coupling circuit 371 may include a capacitor C32. The second AC coupling circuit 371 directly transmits the high-frequency signal in the second differential signal S- to the second differential amplifier circuit (the third operational amplifier 33).

[0097] The DC and low-frequency signals in the first differential signal S+ are coupled to the non-inverting input terminal 311 of the first operational amplifier 31 through the first coupling circuit 34 and the resistor R31, and are coupled to the output terminal 313 of the first operational amplifier 31 after being amplified by the first operational amplifier 31, and are then coupled to the inverting input terminal of the third operational amplifier 33 through the resistor R32. In the first operational amplifier 31, the DC power supply signal output by the first digital-to-analog converter 391 is input to the inverting input terminal 312 of the first operational amplifier 31 through the resistor R33.

[0098] Similarly, the DC and low-frequency signals in the second differential signal S- are coupled to the in-phase input terminal 321 of the second operational amplifier 32 through the second coupling circuit 35 and the resistor R36, and are coupled to the output terminal 323 of the second operational amplifier 32 after being amplified by the second operational amplifier 32, and are then coupled to the in-phase input terminal of the third operational amplifier 33 through the resistor R36. In the second operational amplifier 32, the DC power supply signal output by the second digital-to-analog converter 392 is input to the inverting input terminal 322 of the second operational amplifier 32 through the resistor R37.

[0099] In the present embodiment, capacitor C31 and resistor R32 constitute a first high-pass filter, and capacitor C32 and resistor R36 constitute a second high-pass filter. The cut-off frequency of the first high-pass filter is determined by capacitor C31 and resistor R32, and the cut-off frequency of the second high-pass filter can be determined by capacitor C32 and resistor R36. The above-mentioned first high-pass filter can filter out the DC signal and the low-frequency signal in the first differential signal S+, and directly couple the high-frequency signal in the first differential signal S+ to the third operational amplifier. The separation of the DC signal and the low-frequency signal from the high-frequency signal in the first differential signal S+ is achieved. The above-mentioned second high-pass filter can filter out the DC signal and the low-frequency signal in the second differential signal S-, and directly couple the high-frequency signal in the second differential signal S- to the third operational amplifier. The separation of the DC signal and the low-frequency signal from the high-frequency signal in the second differential signal S- is achieved.

[0100] The first operational amplifier 31 , the second operational amplifier 32 , the third operational amplifier 33 and their corresponding coupling circuits separate the signals of different frequencies of the input differential signal and amplify them respectively.

[0101] Specifically, the high-frequency signal in the first differential signal S+ is coupled to the inverting input terminal of the third operational amplifier 33 through the first AC coupling circuit 361. The high-frequency signal in the second differential signal S- is coupled to the non-inverting input terminal of the third operational amplifier 33 through the second AC coupling circuit 371. The high-frequency signal in the first differential signal S+ and the second differential signal S- directly enters the third operational amplifier 33 for amplification. The DC signal and the low-frequency signal enter the first operational amplifier 31 and the second operational amplifier 32 for amplification, and the DC signal and the low-frequency signal in the first differential signal S+ and the second differential signal S- enter the third operational amplifier 33 for amplification after passing through the first operational amplifier 31 and the second operational amplifier 32.

[0102] In one embodiment, the in-phase signal input terminal of the first operational amplifier 31 is changed from grounding to connecting to the first analog-to-digital converter 391, and the in-phase signal input terminal of the second operational amplifier 32 is changed from grounding to connecting to the second digital-to-analog converter 392, and the DC bias adjustment function is realized by the first analog-to-digital converter 191 and the second analog-to-digital converter 192. When a large DC signal flows into the first differential signal S+ and the second differential signal S-, the DC signal is offset and attenuated by adjusting the voltage output by the first digital-to-analog converter 391 and the second analog-to-digital converter 392. The DC and low-frequency signals are attenuated in the first operational amplifier and the second operational amplifier, and the high-frequency signal is combined and enters the third operational amplifier. The high and low frequency signals are separated, attenuated and then synthesized to obtain amplification from DC to high frequency. In addition, since the third feedback network realizes inter-stage negative feedback, the gain flatness of the DC and low-frequency signals can be achieved. By feeding back the low-frequency signal output by the third operational amplifier to the output ends of the first digital-to-analog converter and the second analog-to-digital converter through the third feedback network, the DC bias value of the signal amplification circuit can be dynamically adjusted, and the broadband amplification function from DC, low frequency to higher frequency (millimeter wave, etc.) and full-band flat amplification characteristics can be realized, thereby improving the flatness of the gain in the entire frequency band.

[0103] The impedance of the first coupling circuit of the signal amplifier circuit matches the impedance of the first feedback network. For example, the parameters of the components of the first feedback network and the parameters of the components in the first coupling circuit are set so that the impedance of the first feedback network and the impedance of the first coupling circuit can ensure that the closed-loop gain meets the design requirements.

[0104] In addition, the resistance values ​​of R32, R39, and R310, and / or the capacitance values ​​of C33 and R33 can be adjusted to ensure that the low-frequency DC gain and the high-frequency AC gain are the same, so that a flat frequency response can be obtained after the high-frequency signal and the low-frequency signal are superimposed, ensuring that the signal is not distorted.

[0105] The size of the resistor R319 in the third feedback network affects the amplification factor of the signal amplifier circuit. The size of the resistor R319 is positively correlated with the gain of the low-frequency signal and the DC signal. The third feedback network can attenuate the low-frequency signal and the DC signal output by the third operational amplifier, which is conducive to making the gain of the full frequency band flat.

[0106] In addition, the inverting input terminal of the third operational amplifier 33 is also grounded through a resistor R315, and the non-inverting input terminal of the third operational amplifier 33 is also grounded through a resistor R318, thereby ensuring that the potentials of the non-inverting input terminal and the inverting input terminal of the third operational amplifier are at a stable reference level.

[0107] Please refer to Figure 5 , Figure 5 for Figure 3The simulation result diagram of the signal amplification circuit of the embodiment shown is as follows: Figure 5 As shown, the simulation results show that the circuit can achieve flat extraction of differential signals in the range of DC to 30GHz, with a flatness of ±1.5dB. In the range of DC to 10kHz, the circuit presents a large input impedance of about tens of kΩ. After 10kHz, the impedance drops sharply. At frequencies above 10kHz, the differential output impedance is about hundreds of ohms, and drops to tens of ohms at higher frequencies.

[0108] In this embodiment, by using the first AC coupling circuit and the second AC coupling circuit, the DC signal, the low-frequency signal and the high-frequency signal in the first differential signal and the second differential signal are separated, and the high-frequency signal is amplified by the third operational amplifier. The DC signal and the low-frequency signal in the differential signal are amplified by the first operational amplifier and the second operational amplifier and then enter the third operational amplifier for conditioning, so as to achieve the separation, attenuation and resynthesis of high and low frequency signals. By processing the high-frequency signal and the low-frequency signal separately, the bandwidth of the entire system can be effectively extended. The first-stage operational amplifier can be used to amplify the low-frequency signal, and the second-stage operational amplifier can process the high-frequency signal. Thus, the signal amplification circuit provided in this embodiment can amplify the signal within a wider frequency range. The high-frequency signal is coupled into the second-stage operational amplifier, which can reduce the influence of the high-frequency signal on the first-stage operational amplifier and enhance stability. By processing the full-band signal in a branch path, the gain of each frequency band can be better controlled and the possibility of oscillation can be reduced.

[0109] Please refer to Figure 6 , Figure 6 This is a structural block diagram of the electronic device provided by the present disclosure. Figure 6 As shown, the electronic device may include a sampler 61, such as Figure 1~Figure 3 Any one of the signal amplification circuits 62 and the display 63 shown in the figure can be various instruments and meters, and can be applied to the fields of wireless communication, power monitoring, measurement systems, and radar technology. Schematically, the electronic device can be an oscilloscope.

[0110] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. It is understood that the terms "first", "second", etc. used in the present application can be used to describe various information or data in this article, but these elements are not limited by these terms. These terms are only used to distinguish the first information from another information. The "and / or" that appears in the present application represents at least one of the connected objects, and the character " / " generally represents that the objects associated before and after are a kind of "or" relationship.

[0111] Those skilled in the art should understand that the scope of disclosure involved in the present disclosure is not limited to the technical solutions formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present disclosure.

[0112] Although several specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure. Certain features described in the context of a separate embodiment can also be implemented in a single embodiment in combination. On the contrary, the various features described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable sub-combination.

[0113] Although the subject matter has been described in language specific to structural features and methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Instead, the specific features and actions described above are merely example forms of implementing the claims.

Claims

1. A signal amplification circuit, characterized in that: include: a first operational amplifier, a second operational amplifier, a third operational amplifier, a first coupling circuit, a second coupling circuit, a first feedback network, a second feedback network, and a third feedback network; wherein, A first signal input terminal of the first operational amplifier is connected to one end of the first coupling circuit, and the other end of the first coupling circuit inputs a first differential signal of a signal to be amplified; The output terminal of the first operational amplifier is connected to the first signal input terminal of the first operational amplifier through the first feedback network; A first signal input terminal of the second operational amplifier is connected to one terminal of the second coupling circuit, and the other terminal of the second coupling circuit inputs a second differential signal of the signal to be amplified; The output terminal of the second operational amplifier is connected to the first signal input terminal of the second operational amplifier through the second feedback network; The output terminal of the first operational amplifier is connected to the inverting input terminal of the third operational amplifier, and the output terminal of the second operational amplifier is connected to the non-inverting input terminal of the third operational amplifier; Wherein, the second signal input terminal of the first operational amplifier is connected to the first digital-to-analog converter, and the second signal input terminal of the second operational amplifier is connected to the second digital-to-analog converter; The output terminal of the third operational amplifier is connected to the second signal input terminal of the first operational amplifier and the second signal input terminal of the second operational amplifier through the third feedback network.

2. The signal amplifying circuit according to claim 1, characterized in that: The first differential signal and the second differential signal include a direct current signal and a low-frequency signal, respectively, or include a direct current signal, a low-frequency signal, and a high-frequency signal, respectively.

3. The signal amplifying circuit according to claim 1, characterized in that: The first coupling circuit and the second coupling circuit respectively include: a DC signal coupling branch and an AC signal coupling branch.

4. The signal amplifying circuit according to claim 1, characterized in that: The third feedback network is a resistor feedback network.

5. The signal amplifying circuit according to claim 1, characterized in that: The output terminal of the first operational amplifier is connected to the first signal input terminal of the first operational amplifier through the first feedback network; The output terminal of the second operational amplifier is connected to the first signal input terminal of the second operational amplifier through the second feedback network.

6. The signal amplifying circuit according to claim 5, characterized in that: The first signal input terminal of the first operational amplifier and the first signal input terminal of the second operational amplifier are inverting input terminals; The second signal input terminal of the first operational amplifier and the second signal input terminal of the second operational amplifier are in-phase input terminals.

7. The signal amplifying circuit according to claim 1, characterized in that: It also includes a first AC coupling circuit and a second AC coupling circuit; wherein, One end of the first AC coupling circuit inputs the first differential signal, and the other end is connected to a signal input end of the third operational amplifier; One end of the second AC coupling circuit inputs the second differential signal, and the other end is connected to another signal input end of the third operational amplifier.

8. The signal amplifying circuit according to claim 7, characterized in that: The output terminal of the first operational amplifier is connected to the second signal input terminal of the first operational amplifier through the first feedback network; The output terminal of the second operational amplifier is connected to the second signal input terminal of the second operational amplifier through the second feedback network; Among them, the first signal input terminal of the first operational amplifier and the first signal input terminal of the second operational amplifier are non-inverting input terminals; the second signal input terminal of the first operational amplifier and the second signal input terminal of the second operational amplifier are inverting input terminals.

9. The signal amplifying circuit according to any one of claims 1 to 8, characterized in that: The impedance of the first coupling circuit matches the impedance of the first feedback network; The impedance of the second coupling circuit matches the impedance of the second feedback network.

10. The signal amplifying circuit according to any one of claims 1 to 8, characterized in that: A first resistor is connected in series between the first coupling circuit and the first signal input terminal of the first operational amplifier, and a second resistor is connected in series between the output terminal of the first operational amplifier and the signal input terminal of the third operational amplifier; A third resistor is connected in series between the second coupling circuit and the input terminal of the second operational amplifier, and a fourth resistor is connected in series between the output terminal of the second operational amplifier and the signal input terminal of the third operational amplifier; wherein, The resistance values ​​of the first resistor, the second resistor, the third resistor and the fourth resistor are equal, and the resistance values ​​match the transmission impedance of the signal to be amplified outside the signal amplifying circuit.

11. An electronic device, characterized in that: The invention comprises the signal amplifying circuit as claimed in any one of claims 1 to 10.

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