Bandwidth limiting circuit and front-end circuit

Abstract

The invention relates to a bandwidth limiting circuit and a front-end circuit. The bandwidth limiting circuit comprises at least two signal transmission paths which are connected in parallel between the signal input end and the signal output end; the at least two signal transmission paths are configured to have different bandwidth ranges; the bandwidth range comprises a first bandwidth range, so that the bandwidth of a signal which is transmitted through a signal transmission path with the first bandwidth range and is output from the signal output end is limited; any one of the at least two signal transmission paths is switched on when the other paths are switched off. According to the embodiment of the invention, unwanted out-of-band high-frequency noise can be suppressed, and the noise is effectively reduced.

Description

Technical Field

[0001] This application relates to the field of electronic technologies, and particularly to a bandwidth limiting circuit and a front-end circuit. Background Art

[0002] In the analog front-end circuits of current measurement devices (such as oscilloscopes, signal sources, etc.), a first-order low-pass filter is generally used to implement bandwidth limitation. However, the out-of-band rejection of the first-order low-pass filter is relatively poor, resulting in high-frequency noise signals outside the band entering the measurement device and causing relatively large noise. Summary of the Invention

[0003] In view of this, embodiments of this application provide a bandwidth limiting circuit and a front-end circuit to solve at least one problem in the background art.

[0004] In a first aspect, embodiments of this application provide a bandwidth limiting circuit, which includes at least two signal transmission paths connected in parallel between a signal input end and a signal output end;

[0005] The at least two signal transmission paths are configured to have different bandwidth ranges; the bandwidth range includes a first bandwidth range, so that the signal transmitted through the signal transmission path with the first bandwidth range and output from the signal output end is bandwidth-limited;

[0006] Any one of the at least two signal transmission paths conducts during the disconnection of the other paths.

[0007] In combination with the first aspect, in an optional embodiment, the signal transmission path includes a first signal transmission path, which is configured to have the first bandwidth range;

[0008] The first signal transmission path includes a first switch module connected in series between the signal input end and the signal output end;

[0009] The first switch module is configured to be controlled to open or close, so that the signal transmission from the signal input end to the signal output end of the first signal transmission path conducts or disconnects.

[0010] In combination with the first aspect, in an optional embodiment, the first switch module includes a first operational amplifier;

[0011] The input end of the first operational amplifier is connected to the signal input end, and the output end of the first operational amplifier is connected to the signal output end.

[0012] In combination with the first aspect, in an optional embodiment, the first operational amplifier includes a first enable control end, which is configured to receive a first control signal;

[0013] The first operational amplifier is configured to be turned on or off under the control of the first control signal.

[0014] Combined with the first aspect, in an alternative embodiment, the first enabling control terminal is connected to at least one of the power terminal, the output terminal, and the bias input terminal of the first operational amplifier.

[0015] Combined with the first aspect, in an alternative embodiment, the first signal transmission path further includes a high-order low-pass filter connected in series with the first switching module;

[0016] The high-order low-pass filter is configured to have the first bandwidth range and the first bandwidth range is adjustable.

[0017] Combined with the first aspect, in an alternative embodiment, the high-order low-pass filter includes a first transconductance amplifier, a second transconductance amplifier, a third transconductance amplifier, a fourth transconductance amplifier, a first capacitor, and a second capacitor;

[0018] The positive input terminal and the negative input terminal of the first transconductance amplifier are respectively configured to input signals, and the positive output terminal and the negative output terminal of the third transconductance amplifier are respectively configured to output signals;

[0019] The negative output terminal of the first transconductance amplifier is respectively connected to the negative input terminal of the second transconductance amplifier, the positive output terminal of the second transconductance amplifier, the first end of the first capacitor, the negative input terminal of the third transconductance amplifier, and the positive output terminal of the fourth transconductance amplifier. The positive output terminal of the first transconductance amplifier is respectively connected to the positive input terminal of the second transconductance amplifier, the negative output terminal of the second transconductance amplifier, the second end of the first capacitor, the positive input terminal of the third transconductance amplifier, and the negative output terminal of the fourth transconductance amplifier. The positive output terminal of the third transconductance amplifier is respectively connected to the first end of the second capacitor and the positive input terminal of the fourth transconductance amplifier. The negative output terminal of the third transconductance amplifier is respectively connected to the second end of the second capacitor and the negative input terminal of the fourth transconductance amplifier.

[0020] Combined with the first aspect, in an alternative embodiment, the signal transmission path includes a second signal transmission path configured to have a second bandwidth range, so that the signal transmitted through the second signal transmission path and input from the signal input terminal is directly output from the signal output terminal or output without bandwidth limitation.

[0021] Combined with the first aspect, in an alternative embodiment, the second signal transmission path includes a second switching module connected in series between the signal input terminal and the signal output terminal;

[0022] The second switching module is configured to be controlled to be turned on or off, so that the signal transmission from the signal input terminal to the signal output terminal of the second signal transmission path is conducted or disconnected.

[0023] In combination with the first aspect, in an alternative embodiment, the second switching module includes a second operational amplifier;

[0024] The input terminal of the second operational amplifier is connected to the signal input terminal, and the output terminal of the second operational amplifier is connected to the signal output terminal.

[0025] In combination with the first aspect, in an alternative embodiment, the second operational amplifier includes a second enable control terminal configured to receive a second control signal;

[0026] The second operational amplifier is configured to be turned on or off under the control of the second control signal.

[0027] In combination with the first aspect, in an alternative embodiment, the second enable control terminal is connected to at least one of a power supply terminal, an output terminal, and a bias input terminal of the second operational amplifier.

[0028] In a second aspect, an embodiment of the present application provides a front-end circuit, where the front-end circuit includes a control processing module and the above bandwidth limiting circuit;

[0029] The control processing module is configured to output a control signal to the bandwidth limiting circuit so that any one of at least two signal transmission paths of the bandwidth limiting circuit is conducted during the disconnection of other paths.

[0030] The beneficial effects brought by the technical solution provided by the embodiment of the present application include: by setting a signal transmission path with a first bandwidth range, unwanted out-of-band high-frequency noise can be suppressed and will not enter the measuring device, effectively reducing the noise. And by connecting at least two signal transmission paths in parallel between the signal input terminal and the signal output terminal, and at least two signal transmission paths are configured to have different bandwidth ranges, it is possible to limit or not limit the bandwidth of the output signal differently, expanding the applicability and application range.

[0031] Additional aspects and advantages of the embodiments of the present application will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings herein are incorporated into and constitute a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application. To more clearly illustrate the technical solutions of the embodiments of the present application, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings. These drawings and textual descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. In the drawings:

[0033] Figure 1 In (a) therein is a 20 MHz signal captured using an 8 GHz bandwidth;

[0034] Figure 1 In (b) therein is a 20 MHz signal captured using a 100 MHz bandwidth;

[0035] Figure 2 In (a) therein is the front-end circuit of Example 1 in the embodiments of the present application;

[0036] Figure 2 In (b) therein is the front-end circuit of Example 2 in the embodiments of the present application;

[0037] Figure 3 is the principle block diagram of a specific example of the bandwidth limiting circuit in the embodiments of the present application;

[0038] Figure 4 is the principle block diagram of another specific example of the bandwidth limiting circuit in the embodiments of the present application;

[0039] Figure 5 is the principle block diagram of a specific example of the high-order low-pass filter in the embodiments of the present application;

[0040] Figure 6 is the principle block diagram of a specific example of the front-end circuit in the embodiments of the present application. Detailed implementation manners

[0041] To make the technical solutions and beneficial effects of the embodiments of the present application more obvious and understandable, detailed descriptions will be given below by way of listing specific embodiments. Among them, the accompanying drawings are not necessarily drawn to scale, and local features can be enlarged or reduced to more clearly show the details of the local features; unless otherwise defined, the technical and scientific terms used herein have the same meanings as those of the technical and scientific terms in the technical field to which the embodiments of the present application belong.

[0042] It should be noted that terms such as "first", "second", etc. may be used in this document to describe various components, but these components are not limited by these terms. These terms are only used to distinguish the first component from another component. When describing the "first", it does not necessarily mean the existence of the "second"; and when discussing the "second", it does not indicate that the "first" necessarily exists in this application. The singular forms of "a", "an", and "the" may also be intended to include the plural forms, unless the context clearly indicates otherwise. The term "comprising" is used to determine the existence of the included features, but does not exclude the existence or addition of one or more other features. The term "and / or" includes any and all combinations of the related listed items. The term "connected" can be a direct connection between two components or an indirect connection established through other components.

[0043] If the bandwidth of an oscilloscope is too high, it will pick up high-frequency noise during measurement, thus affecting the measurement result and reducing the measurement accuracy. Taking the measurement of power supply ripple as an example, when measuring some low-frequency ripple signals in the power supply, since a high-bandwidth oscilloscope will allow high-frequency noise to enter and interfere with the observation, the measurement effect is not good. Figure 1 In (a) and (b) respectively show the 20MHz signals captured using an 8GHz bandwidth and a 100MHz bandwidth. Figure 1 As can be seen from (a) and (b) in, it is more appropriate to use a 100MHz bandwidth for measurement, which can obtain a clean signal, while the signal obtained by using an 8GHz bandwidth for measurement contains more noise, resulting in the signal becoming wider and inaccurate peak measurement.

[0044] Therefore, filters are used to provide different bandwidth limitations to form a front-end circuit to filter out unwanted noise from the input waveform and reduce the noise bandwidth of the measurement device (such as an oscilloscope, etc.). For example, the bandwidth-limiting filter includes a hardware filter and a software filter. All bandwidth-limiting filters can be controlled to be started or turned off according to actual needs. Analog filters are not limited by the sampling rate and have a relatively strong high-frequency suppression ability, while digital filters require a large amount of DSP logic resources and a very large amount of computing power.

[0045] As a specific example, as Figure 2 shown in (a) in, the front-end circuit includes a first input-stage buffer amplifier circuit a1, a first variable-gain amplifier circuit a2, a first bandwidth-limiting circuit a3, and a first output-stage buffer amplifier circuit a4 connected in series in sequence between the signal input terminal and the signal output terminal.

[0046] As another specific example, as Figure 2As shown in (b) therein, the front-end circuit includes a second input-stage buffer amplification circuit b1, a second variable-gain amplification circuit b2, a second output-stage buffer amplification circuit b3, and a second bandwidth-limiting circuit b4 that are sequentially connected in series between the signal input terminal and the signal output terminal.

[0047] Among them, the main functions of the first input-stage buffer amplification circuit a1 and the second input-stage buffer amplification circuit b1 are impedance transformation. In order to reduce noise interference such as that from power lines, the input-stage buffer amplification circuit can convert a single-ended signal into a differential signal output through impedance transformation. Additionally, the input-stage buffer amplification circuit can include an input terminal for a bias signal OFFSET to adjust the oscilloscope bias according to the bias signal. The first variable-gain amplification circuit a2 and the second variable-gain amplification circuit b2 amplify or attenuate the signal by different amplitudes to meet the gain configuration requirements of multiple gain levels of the oscilloscope. The variable-gain amplification circuit can achieve different gain selections through the series or parallel connection of multiple variable-gain amplifiers. The bandwidth-limiting circuit can be selectively connected before or after the output-stage buffer amplification circuit according to actual needs. For example, the first bandwidth-limiting circuit a3 is connected between the first variable-gain amplification circuit a2 and the first output-stage buffer amplification circuit a4, and the second bandwidth-limiting circuit b4 is connected between the second output-stage buffer amplification circuit b3 and the signal output terminal. After the signal passes through the variable-gain amplification circuit, for the overall noise performance, the bandwidth-limiting circuit can filter out high-frequency noise. The bandwidth-limiting circuit can be set according to actual bandwidth requirements.

[0048] If a first-order low-pass filter is used to provide bandwidth limitation, due to the poor out-of-band rejection of the first-order low-pass filter, high-frequency noise signals outside the band enter the measurement device (such as an oscilloscope), resulting in a large amount of noise.

[0049] Therefore, an embodiment of the present application provides a bandwidth-limiting circuit that can be applied to the front-end circuit of measurement devices such as oscilloscopes and signal sources. As Figure 3 shown, the bandwidth-limiting circuit includes at least two signal transmission paths connected in parallel between the signal input terminal and the signal output terminal;

[0050] The at least two signal transmission paths are configured to have different bandwidth ranges; the bandwidth range includes a first bandwidth range such that the signal transmitted through the signal transmission path having the first bandwidth range and output from the signal output terminal is bandwidth-limited;

[0051] Any one of the at least two signal transmission paths is conductive during the disconnection of the other paths.

[0052] In the embodiments of the present application, the different bandwidth ranges of at least two signal transmission paths may include multiple types. For example, it may include a first bandwidth range, a second bandwidth range, and other bandwidth ranges. The signal transmission path with the first bandwidth range can have bandwidth limitation to suppress unwanted out-of-band high-frequency noise. The signal transmission path with the second bandwidth range can be a high-bandwidth path, and a maximum signal bandwidth can be set so that the signal input from the signal input end can be directly output from the signal output end without bandwidth limitation.

[0053] Any one of the at least two signal transmission paths can be turned on during the disconnection of the other paths. That is, if the signal transmission from the signal input end to the signal output end of any one of the at least two signal transmission paths is controlled to be turned on, the signal transmission from the signal input end to the signal output end of the other signal transmission paths is controlled to be turned off.

[0054] In the embodiments of the present application, by setting the signal transmission path with the first bandwidth range, unwanted out-of-band high-frequency noise can be suppressed and will not enter the measuring device, effectively reducing the noise. And by connecting at least two signal transmission paths in parallel between the signal input end and the signal output end, and the at least two signal transmission paths are configured to have different bandwidth ranges, the bandwidth of the output signal can be differently limited or not limited, expanding the applicability and application range.

[0055] In an alternative embodiment, as Figure 4 shown, the signal transmission path includes a first signal transmission path TR1, which is configured to have a first bandwidth range;

[0056] The first signal transmission path TR1 includes a first switch module 10 connected in series between the signal input end and the signal output end;

[0057] The first switch module 10 is configured to be controlled to open or close, so that the signal transmission from the signal input end to the signal output end of the first signal transmission path TR1 is turned on or off.

[0058] In the embodiments of the present application, the first switch module 10 may include at least one of an operational amplifier, a semiconductor switching device, and other devices capable of realizing a switching function. In the embodiments of the present application, by controlling the first switch module to open, the on-control of the signal transmission from the signal input end to the signal output end of the first signal transmission path is realized, and by controlling the first switch module to disconnect, the off-control of the signal transmission from the signal input end to the signal output end of the first signal transmission path is realized, thereby realizing the on-off control of the first signal transmission path.

[0059] In an alternative embodiment, the first switch module 10 includes a first operational amplifier OTA1;

[0060] The input terminal of the first operational amplifier OTA1 is connected to the signal input terminal, and the output terminal of the first operational amplifier OTA1 is connected to the signal output terminal.

[0061] In the embodiment of the present application, the signal input terminal may include a differential first signal input terminal VIP and a second signal output terminal VIN. The signal output terminal may include a differential first signal output terminal IOP and a second signal output terminal ION. The first operational amplifier OTA1 may include two differential input terminals and two output terminals. The two input terminals may be respectively connected to the first signal input terminal VIP and the second signal output terminal VIN in a one-to-one correspondence, and the two output terminals may be respectively connected to the first signal output terminal IOP and the second signal output terminal ION in a one-to-one correspondence. The first operational amplifier OTA1 may be a differential amplifier, a transconductance amplifier or other operational amplifiers. A transconductance amplifier is an amplifier with voltage input and current output. In the embodiment of the present application, by using the first operational amplifier and the differential method, the noise interference such as that from the power supply line is reduced. And by using a transconductance amplifier, the distortion, offset and thermal effects can also be reduced, and the measurement accuracy can be improved.

[0062] In an alternative embodiment, the first operational amplifier OTA1 includes a first enable control terminal configured to receive a first control signal;

[0063] The first operational amplifier OTA1 is configured to be turned on or off under the control of the first control signal.

[0064] In the embodiment of the present application, by providing the first enable control terminal, the first control signal can be received, and the control of turning on and off the first operational amplifier under the control of the first control signal is realized, thereby realizing the on-off control of the first signal transmission path.

[0065] As a specific example, the first enable control terminal is connected to the power supply terminal of the first operational amplifier OTA1.

[0066] In the embodiment of the present application, the first control signal received by the first enable control terminal can control the power-on or power-off of the first operational amplifier OTA1 to realize the control of turning on or off the first operational amplifier OTA1. The embodiment of the present application can be used for an operational amplifier with large power consumption and can significantly save power consumption.

[0067] As another specific example, the first enable control terminal is connected to the output terminal of the first operational amplifier OTA1.

[0068] In the embodiments of the present application, the first enabling control terminal can be respectively connected to the first signal output terminal IOP and the second signal output terminal ION of the first operational amplifier OTA1. The first control signal received through the first enabling control terminal can control the output of the first operational amplifier OTA1 to be pulled high or low, so that the subsequent-stage circuit receives a fixed common-mode level, thereby realizing the control of turning on or off the first operational amplifier OTA1. The embodiments of the present application can realize quickly turning on and off the first operational amplifier OTA1, improve the switching speed of the operational amplifier, and can be used for low-power operational amplifiers and signal transmission paths that require quick startup.

[0069] As another specific example, the first enabling control terminal is connected to the bias input terminal of the first operational amplifier OTA1.

[0070] In the embodiments of the present application, the bias input terminal of the first operational amplifier OTA1 can be the internal bias voltage input terminal or bias current input terminal thereof, and is used to input a bias voltage or bias current to the first operational amplifier OTA1. The first control signal received through the first enabling control terminal can control the loading and removal of the bias voltage or bias current, so as to achieve the control of turning on and off the first operational amplifier OTA1.

[0071] In an alternative embodiment, as Figure 4 shown, the first signal transmission path TR1 further includes a high-order low-pass filter 20 connected in series with the first switch module 10;

[0072] The high-order low-pass filter 20 is configured to have a first bandwidth range and the first bandwidth range is adjustable.

[0073] In the embodiments of the present application, the high-order low-pass filter 20 can be connected in series between the signal input terminals (such as the first signal input terminal VIP and the second signal input terminal VIN) and the first operational amplifier OTA1, or can be connected in series between the first operational amplifier OTA1 and the signal output terminals (such as the first signal output terminal IOP and the second signal output terminal ION). By adjusting the first bandwidth range of the high-order low-pass filter, a first signal transmission path with strong out-of-band suppression can be realized under different first bandwidth ranges, so that the analog front-end bandwidth can be controlled, and at the same time, the out-of-band suppression is relatively good, so that high-frequency noise is suppressed and the noise performance is good. By using a high-order low-pass filter with adjustable bandwidth, the different bandwidth requirements of customers can be flexibly met, resources can be saved, and there is no need to design multiple bandwidth limitations.

[0074] The high-order low-pass filter 20 can be set according to actual requirements. As a specific example, the high-order low-pass filter 20 adopts a second-order transconductance-capacitance (abbreviation: Gm-C) low-pass filter, which has the advantages of low power and high operating frequency.

[0075] As Figure 5 shown, the high-order low-pass filter 20 includes a first transconductance amplifier Gm1, a second transconductance amplifier Gm2, a third transconductance amplifier Gm3, a fourth transconductance amplifier Gm4, a first capacitor C1, and a second capacitor C2;

[0076] The positive input terminal and the negative input terminal of the first transconductance amplifier Gm1 are respectively configured to input signals, and the positive output terminal and the negative output terminal of the third transconductance amplifier Gm3 are respectively configured to output signals;

[0077] The negative output terminal of the first transconductance amplifier Gm1 is respectively connected to the negative input terminal of the second transconductance amplifier Gm2, the positive output terminal of the second transconductance amplifier Gm2, the first end of the first capacitor C1, the negative input terminal of the third transconductance amplifier Gm3, and the positive output terminal of the fourth transconductance amplifier Gm4. The positive output terminal of the first transconductance amplifier Gm1 is respectively connected to the positive input terminal of the second transconductance amplifier Gm2, the negative output terminal of the second transconductance amplifier Gm2, the second end of the first capacitor C1, the positive input terminal of the third transconductance amplifier Gm3, and the negative output terminal of the fourth transconductance amplifier Gm4. The positive output terminal of the third transconductance amplifier Gm3 is respectively connected to the first end of the second capacitor C2 and the positive input terminal of the fourth transconductance amplifier Gm4. The negative output terminal of the third transconductance amplifier Gm3 is respectively connected to the second end of the second capacitor C2 and the negative input terminal of the fourth transconductance amplifier Gm4.

[0078] In the embodiment of the present application, by adjusting the first capacitor and the second capacitor, different limiting bandwidths are selected, thereby realizing the adjustability of the limiting bandwidth.

[0079] In an alternative embodiment, as Figure 4 shown, the signal transmission path includes a second signal transmission path TR2, which is configured to have a second bandwidth range, so that the signal transmitted through the second signal transmission path TR2 and input from the signal input terminal is directly output from the signal output terminal without being limited in bandwidth.

[0080] In the embodiment of the present application, the second bandwidth range may be a high bandwidth, such as the maximum signal bandwidth. Directly can mean that the signal output from the signal output terminal is the original signal input from the signal input terminal. Not being limited in bandwidth can mean that the signal output from the signal output terminal is the signal obtained by processing the signal input from the signal input terminal through at least one of amplification, first-order low-pass filtering, etc. By setting the second signal transmission path in the embodiment of the present application, the applicability and application range are expanded.

[0081] In an alternative embodiment, the second signal transmission path TR2 includes a second switch module 30 connected in series between the signal input terminal and the signal output terminal;

[0082] The second switch module 30 is configured to be controlled to open or close, so as to conduct or disconnect the signal transmission from the slave signal input end to the signal output end of the second signal transmission path TR2.

[0083] In the embodiment of the present application, the structure of the second switch module 30 and the first switch module 10 may be the same or different. The second switch module 30 may include at least one of an operational amplifier, a semiconductor switching device, and other devices capable of implementing a switching function. The function of the second switch module 30 and the first switch module 10 may be the same, that is, to realize the on-off control of the second signal transmission path.

[0084] In an alternative embodiment, the second switch module 30 includes a second operational amplifier OTA2;

[0085] The input end of the second operational amplifier OTA2 is connected to the signal input end, and the output end of the second operational amplifier OTA2 is connected to the signal output end.

[0086] In the embodiment of the present application, the structure of the second operational amplifier OTA2 and the first operational amplifier OTA1 may be the same or different. The second operational amplifier OTA2 may include two differential input ends and two output ends, so as to reduce noise. The second operational amplifier OTA2 may be a differential amplifier, a transconductance amplifier, or other operational amplifiers, so as to reduce distortion, offset, and thermal effects and improve measurement accuracy.

[0087] In the embodiment of the present application, the opening and closing manner of the second operational amplifier OTA2 may be the same as that of the first operational amplifier OTA1. Specifically: the second operational amplifier OTA2 includes a second enable control end, which is configured to receive a second control signal; the second operational amplifier OTA2 is configured to be opened or closed under the control of the second control signal.

[0088] As a specific example, the second enable control end is connected to the power supply end of the second operational amplifier OTA2, so that it can be used for an operational amplifier with high power consumption, and the power consumption can be significantly saved.

[0089] As another specific example, the second enable control end is connected to the output end of the second operational amplifier OTA2, so that it can be used for a low-power operational amplifier and a signal transmission path that needs to be quickly started.

[0090] As yet another specific example, the second enable control end is connected to the bias input end of the second operational amplifier OTA2 to achieve the control of the opening and closing of the first operational amplifier OTA1.

[0091] In the embodiment of the present application, one of the second signal transmission path TR2 and the first signal transmission path TR1 is disconnected during the conduction of the other, that is, the first signal transmission path TR1 is configured to be disconnected during the conduction of the second signal transmission path TR2, and the second signal transmission path TR2 is configured to be disconnected during the conduction of the first signal transmission path TR1. When bandwidth limitation is required, the second operational amplifier OTA2 can be controlled to be turned off and the first operational amplifier OTA1 can be turned on. At this time, the first signal transmission path TR1 is conducting and the second signal transmission path TR2 is disconnected, and the signal can only reach the signal output terminal after passing through the high-order low-pass filter 20 and the first operational amplifier OTA1. In this way, the signal bandwidth of the bandwidth limitation circuit is determined by the first signal transmission path TR1. The bandwidth of the high-order low-pass filter can be adjusted, and the bandwidth of the output signal will change accordingly, and the unwanted high-frequency noise will be suppressed, improving the measurement accuracy. When bandwidth limitation is not required, the second operational amplifier OTA2 can be controlled to be turned on and the first operational amplifier OTA1 can be turned off. At this time, the first signal transmission path TR1 is disconnected and the second signal transmission path TR2 is conducting, and the signal can only reach the signal output terminal after passing through the second operational amplifier OTA2. In this way, the signal bandwidth of the bandwidth limitation circuit is determined by the second signal transmission path TR2.

[0092] The embodiment of the present application also provides a front-end circuit, which can be applied to instruments such as oscilloscopes and signal sources. As Figure 6 shown, the front-end circuit 001 includes a control processing module 200 and the above-mentioned bandwidth limitation circuit 100;

[0093] The control processing module 200 is configured to output a control signal to the bandwidth limitation circuit 100, so that any one of at least two signal transmission paths of the bandwidth limitation circuit 100 is conducting during the disconnection of other paths.

[0094] In the embodiment of the present application, the control processing module 200 can output a control word to the first enable control end of the first operational amplifier OTA1 of the first signal transmission path TR1 and the second enable control end of the second operational amplifier OTA2 of the second signal transmission path TR2 through a register, so that the first operational amplifier OTA1 is turned on and the second operational amplifier OTA2 is turned off, or the first operational amplifier OTA1 is turned off and the second operational amplifier OTA2 is turned on, thereby realizing the adjustment and control of the bandwidth limitation of the bandwidth limitation circuit 100. And by adopting a register, the control speed is improved.

[0095] It should be noted that among the technical features of the technical solutions recorded in the embodiments of the present application, any combination can be made without conflict.

[0096] It should be understood that the above embodiments are all exemplary and do not cover all possible implementation manners included in the claims. Without departing from the scope of the present disclosure, various deformations and changes can be made based on the above embodiments. Similarly, various technical features of the above embodiments can be arbitrarily combined to form additional embodiments of the present application that may not be clearly described. Therefore, the above embodiments only represent several implementation manners of the present application and do not limit the protection scope of the patent of the present application.

Claims

1. A bandwidth limiting circuit, characterized in that, The bandwidth limiting circuit includes at least two signal transmission paths connected in parallel between the signal input end and the signal output end; At least two signal transmission paths are configured to have different bandwidth ranges; the bandwidth range includes a first bandwidth range, so that the signal transmitted through the signal transmission path having the first bandwidth range and output from the signal output end is bandwidth-limited; Any one of the at least two signal transmission paths is turned on during the disconnection of the other paths.

2. The bandwidth limiting circuit according to claim 1, characterized in that, The signal transmission path includes a first signal transmission path, which is configured to have the first bandwidth range; The first signal transmission path includes a first switch module connected in series between the signal input end and the signal output end; The first switch module is configured to be controlled to be turned on or off, so that the signal transmission from the signal input end to the signal output end of the first signal transmission path is turned on or off.

3. The bandwidth limiting circuit according to claim 2, characterized in that, The first switch module includes a first operational amplifier; The input end of the first operational amplifier is connected to the signal input end, and the output end of the first operational amplifier is connected to the signal output end.

4. The bandwidth limiting circuit according to claim 3, characterized in that, The first operational amplifier includes a first enable control end, which is configured to receive a first control signal; The first operational amplifier is configured to be turned on or off under the control of the first control signal.

5. The bandwidth limiting circuit according to claim 4, characterized in that, The first enable control end is connected to at least one of the power supply end, the output end and the bias input end of the first operational amplifier.

6. The bandwidth limiting circuit according to claim 2, characterized in that, The first signal transmission path further includes a high-order low-pass filter connected in series with the first switch module; The high-order low-pass filter is configured to have the first bandwidth range and the first bandwidth range is adjustable.

7. The bandwidth limiting circuit according to claim 6, characterized in that, The high-order low-pass filter includes a first transconductance amplifier, a second transconductance amplifier, a third transconductance amplifier, a fourth transconductance amplifier, a first capacitor and a second capacitor; The positive input end and the negative input end of the first transconductance amplifier are respectively configured to input signals, and the positive output end and the negative output end of the third transconductance amplifier are respectively configured to output signals; The negative output end of the first transconductance amplifier is respectively connected to the negative input end of the second transconductance amplifier, the positive output end of the second transconductance amplifier, the first end of the first capacitor, the negative input end of the third transconductance amplifier and the positive output end of the fourth transconductance amplifier. The positive output end of the first transconductance amplifier is respectively connected to the positive input end of the second transconductance amplifier, the negative output end of the second transconductance amplifier, the second end of the first capacitor, the positive input end of the third transconductance amplifier and the negative output end of the fourth transconductance amplifier. The positive output end of the third transconductance amplifier is respectively connected to the first end of the second capacitor and the positive input end of the fourth transconductance amplifier. The negative output end of the third transconductance amplifier is respectively connected to the second end of the second capacitor and the negative input end of the fourth transconductance amplifier.

8. The bandwidth limiting circuit according to any one of claims 1-7, characterized in that, The signal transmission path includes a second signal transmission path, which is configured to have a second bandwidth range, so that the signal transmitted through the second signal transmission path and input from the signal input end is directly or non-bandwidth-limitedly output from the signal output end.

9. The bandwidth limiting circuit according to claim 8, characterized in that, The second signal transmission path includes a second switch module connected in series between the signal input end and the signal output end; The second switching module is configured to be controlled to open or close, so as to conduct or disconnect the signal transmission from the signal input end to the signal output end of the second signal transmission path.

10. The bandwidth limiting circuit according to claim 9, characterized in that, The second switching module includes a second operational amplifier; The input end of the second operational amplifier is connected to the signal input end, and the output end of the second operational amplifier is connected to the signal output end.

11. The bandwidth limiting circuit according to claim 10, characterized in that, The second operational amplifier includes a second enable control end, which is configured to receive a second control signal; The second operational amplifier is configured to be opened or closed under the control of the second control signal.

12. The bandwidth limiting circuit according to claim 11, characterized in that, The second enable control end is connected to at least one of the power supply end, the output end and the bias input end included in the second operational amplifier.

13. A front-end circuit, characterized in that, The front-end circuit includes a control processing module and the bandwidth limiting circuit according to any one of claims 1-12; The control processing module is configured to output a control signal to the bandwidth limiting circuit, so that any one of at least two signal transmission paths of the bandwidth limiting circuit is conducted during the disconnection of other paths.

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