Bandwidth limiting circuit and front-end circuit

Abstract

The present application relates to a bandwidth limiting circuit and a front-end circuit. The bandwidth limiting circuit comprises at least two signal transmission paths connected in parallel between a signal input end and a signal output end. The at least two signal transmission paths are configured to have different bandwidth ranges. The bandwidth ranges include a first bandwidth range, so that the bandwidth of a signal transmitted via the signal transmission path having the first bandwidth range and outputted from the signal output end is limited. Any one of the at least two signal transmission paths is connected when other paths are disconnected.

Description

Bandwidth limiting circuit and front-end circuit

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 202311753803X, filed on December 19, 2023, entitled “Bandwidth Limiting Circuit and Front-End Circuit,” the entire text of which is incorporated herein by reference. Technical Field

[0003] The present application relates to the field of electronic technology, and in particular to a bandwidth limiting circuit and a front-end circuit. Background Art

[0004] Currently, the analog front-end circuits of measurement devices (such as oscilloscopes and signal sources) generally use first-order low-pass filters to achieve bandwidth limitation. However, first-order low-pass filters have poor out-of-band rejection, causing high-frequency noise signals outside the band to enter the measurement device, causing significant noise.

[0005] Summary of the Invention

[0006] In view of this, embodiments of the present application provide a bandwidth limiting circuit and a front-end circuit to solve at least one problem existing in the background technology.

[0007] In a first aspect, an embodiment of the present application provides a bandwidth limiting circuit, wherein the bandwidth limiting circuit includes at least two signal transmission paths connected in parallel between a signal input terminal and a signal output terminal;

[0008] At least two signal transmission paths are configured to have different bandwidth ranges; the bandwidth ranges include 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;

[0009] Any one of the at least two signal transmission paths is turned on while the other one is turned off.

[0010] In conjunction with the first aspect, in an optional implementation manner, the signal transmission path includes a first signal transmission path configured to have the first bandwidth range;

[0011] The first signal transmission path includes a first switch module connected in series between the signal input end and the signal output end;

[0012] The first switch module is configured to be controlled to be opened or closed, so as to enable or disconnect the signal transmission from the signal input end to the signal output end of the first signal transmission path.

[0013] In combination with the first aspect, in an optional implementation manner, the first switch module includes a first operational amplifier;

[0014] The input terminal of the first operational amplifier is connected to the signal input terminal, and the output terminal of the first operational amplifier is connected to the signal output terminal.

[0015] In combination with the first aspect, in an optional implementation manner, the first operational amplifier includes a first enable control terminal configured to receive a first control signal;

[0016] The first operational amplifier is configured to be turned on or off under the control of the first control signal.

[0017] In combination with the first aspect, in an optional implementation manner, the first enable control terminal is connected to at least one terminal of the first operational amplifier including a power supply terminal, an output terminal, and a bias input terminal.

[0018] In combination with the first aspect, in an optional implementation manner, the first signal transmission path further includes a high-order low-pass filter connected in series with the first switch module;

[0019] The high-order low-pass filter is configured to have the first bandwidth range, and the first bandwidth range is adjustable.

[0020] In combination with the first aspect, in an optional implementation manner, 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;

[0021] The positive input terminal and the negative input terminal of the first transconductance amplifier are respectively configured as input signals, and the positive output terminal and the negative output terminal of the third transconductance amplifier are respectively configured as output signals;

[0022] 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 terminal 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 terminal 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 terminal of the second capacitor and the positive input terminal of the fourth transconductance amplifier, and the negative output terminal of the third transconductance amplifier is respectively connected to the second terminal of the second capacitor and the negative input terminal of the fourth transconductance amplifier.

[0023] In combination with the first aspect, in an optional embodiment, 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 output from the signal output end directly or without bandwidth restriction.

[0024] In combination with the first aspect, in an optional implementation manner, the second signal transmission path includes a second switch module connected in series between the signal input end and the signal output end;

[0025] The second switch module is configured to be controlled to be opened or closed, so as to enable or disconnect the signal transmission from the signal input end to the signal output end of the second signal transmission path.

[0026] In combination with the first aspect, in an optional implementation manner, the second switch module includes a second operational amplifier;

[0027] An input terminal of the second operational amplifier is connected to the signal input terminal, and an output terminal of the second operational amplifier is connected to the signal output terminal.

[0028] In combination with the first aspect, in an optional implementation manner, the second operational amplifier includes a second enable control terminal configured to receive a second control signal;

[0029] The second operational amplifier is configured to be turned on or off under the control of the second control signal.

[0030] In combination with the first aspect, in an optional implementation manner, the second enable control terminal is connected to at least one terminal of the second operational amplifier including a power supply terminal, an output terminal, and a bias input terminal.

[0031] In a second aspect, an embodiment of the present application provides a front-end circuit, the front-end circuit comprising a control processing module and the above-mentioned bandwidth limiting circuit;

[0032] The control processing module is configured to output a control signal to the bandwidth limiting circuit to enable any one of the at least two signal transmission paths of the bandwidth limiting circuit to be turned on while the other path is turned off.

[0033] The technical solutions provided by the embodiments of the present application offer beneficial effects including: by providing a signal transmission path with a first bandwidth range, unwanted out-of-band high-frequency noise is suppressed and prevented from entering the measurement device, effectively reducing noise. Furthermore, by connecting at least two signal transmission paths in parallel between the signal input and output terminals, and by configuring the at least two signal transmission paths with different bandwidth ranges, the bandwidth of the output signal can be differently limited or unrestricted, thereby expanding its applicability and scope of application.

[0034] Additional aspects and advantages of the embodiments of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings herein are incorporated into and constitute a part of the specification, illustrating embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application. In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. These drawings and text 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 reference to specific embodiments. In the drawings:

[0036] Figure 1 (a) shows a 20 MHz signal captured using an 8 GHz bandwidth;

[0037] (b) in Figure 1 shows a 20 MHz signal captured using a 100 MHz bandwidth;

[0038] FIG2 (a) is a front-end circuit of Example 1 in an embodiment of the present application;

[0039] FIG2( b ) is a front-end circuit of Example 2 in an embodiment of the present application;

[0040] FIG3 is a principle block diagram of a specific example of a bandwidth limiting circuit in an embodiment of the present application;

[0041] FIG4 is a principle block diagram of another specific example of a bandwidth limiting circuit in an embodiment of the present application;

[0042] FIG5 is a principle block diagram of a specific example of a high-order low-pass filter in an embodiment of the present application;

[0043] FIG6 is a principle block diagram of a specific example of a front-end circuit in an embodiment of the present application. DETAILED DESCRIPTION

[0044] To make the technical solutions and beneficial effects of the embodiments of the present application more clearly understood, the following detailed description is given by way of enumerating specific embodiments. The accompanying drawings are not necessarily drawn to scale, and local features may be enlarged or reduced to more clearly illustrate the details of the local features. Unless otherwise defined, the technical and scientific terms used herein have the same meanings as those in the technical field to which the embodiments of the present application belong.

[0045] It should be noted that the terms "first", "second", etc. may be used in this document to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. When describing "first", it does not necessarily mean that there is a "second"; and when discussing "second", it does not mean that there is necessarily a "first" in this application. The singular forms "one", "an" and "said / the" may also be intended to include plural forms, unless the context clearly indicates otherwise. The term "includes" 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 relevant listed items. The term "connected" can be a direct connection between two components or an indirect connection established through other components.

[0046] If the oscilloscope's bandwidth is too high, it will pick up high-frequency noise during measurements, affecting the results and reducing measurement accuracy. For example, when measuring low-frequency ripple signals in a power supply, a high-bandwidth oscilloscope can interfere with observation by allowing high-frequency noise to enter, resulting in poor measurement results. Figures 1 (a) and (b) show a 20MHz signal captured using 8GHz and 100MHz bandwidths, respectively. As can be seen in Figures 1 (a) and (b), the 100MHz bandwidth is more suitable for measurement, producing a clean signal. The 8GHz bandwidth, however, produces a signal with more noise, resulting in a wider signal and inaccurate peak measurements.

[0047] To this end, filters with varying bandwidth limits are used to form front-end circuits, filtering out unwanted noise from the input waveform and reducing the noise bandwidth of measurement devices such as oscilloscopes. Bandwidth-limiting filters, for example, include both hardware and software filters. All bandwidth-limiting filters can be enabled or disabled based on actual needs. Analog filters are not limited by sampling rate and offer strong high-frequency rejection capabilities, while digital filters require significant DSP logic resources and a high computational workload.

[0048] As a specific example, as shown in (a) in Figure 2, 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 between the signal input end and the signal output end.

[0049] As another specific example, as shown in (b) in Figure 2, the front-end circuit includes a second input-stage buffer amplifier circuit b1, a second variable gain amplifier circuit b2, a second output-stage buffer amplifier circuit b3 and a second bandwidth limiting circuit b4 connected in series between the signal input end and the signal output end.

[0050] The primary function of the first input-stage buffer amplifier circuit a1 and the second input-stage buffer amplifier circuit b1 is impedance transformation. To reduce noise interference from power lines and other sources, the input-stage buffer amplifier circuit can convert single-ended signals into differential output signals through impedance transformation. Furthermore, the input-stage buffer amplifier circuit can include an input for an offset signal OFFSET, which is used to adjust the oscilloscope offset based on the offset signal. The first variable-gain amplifier circuit a2 and the second variable-gain amplifier circuit b2 amplify or attenuate the signal at varying amplitudes to meet the oscilloscope's multi-level gain configuration requirements. The variable-gain amplifier circuit can achieve different gain settings by connecting multiple variable-gain amplifiers in series or in parallel. The bandwidth limiting circuit can be connected before or after the output-stage buffer amplifier circuit, depending on actual requirements. For example, the first bandwidth limiting circuit a3 is connected between the first variable-gain amplifier circuit a2 and the first output-stage buffer amplifier circuit a4, while the second bandwidth limiting circuit b4 is connected between the second output-stage buffer amplifier circuit b3 and the signal output terminal. After the signal passes through the variable-gain amplifier circuit, the bandwidth limiting circuit can filter out high-frequency noise to improve overall noise performance. The bandwidth limiting circuit can be configured based on actual bandwidth requirements.

[0051] If a first-order low-pass filter is used to provide bandwidth limitation, since the first-order low-pass filter has poor out-of-band suppression, high-frequency noise signals out of the band enter the measuring device (such as an oscilloscope), resulting in relatively large noise.

[0052] To this end, an embodiment of the present application provides a bandwidth limiting circuit that can be applied to the front-end circuit of a measurement device such as an oscilloscope or a signal source. As shown in FIG3 , the bandwidth limiting circuit includes at least two signal transmission paths connected in parallel between a signal input terminal and a signal output terminal;

[0053] At least two signal transmission paths are configured to have different bandwidth ranges; the bandwidth ranges include 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 terminal is bandwidth-limited;

[0054] Any one of the at least two signal transmission paths is turned on while the other one is turned off.

[0055] In the embodiment of the present application, the different bandwidth ranges of the at least two signal transmission paths may include multiple types, for example, including a first bandwidth range, a second bandwidth range, and other bandwidth ranges. The signal transmission path with the first bandwidth range may be bandwidth-limited to suppress unwanted out-of-band high-frequency noise. The signal transmission path with the second bandwidth range may be a high-bandwidth path and may be set with a maximum signal bandwidth so that a signal input from the signal input end can be output from the signal output end directly or without bandwidth restriction.

[0056] Any one of the at least two signal transmission paths is turned on while the other is disconnected. This may be the case where 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, then the signal transmission from the signal input end to the signal output end of the other signal transmission paths is controlled to be disconnected.

[0057] In the embodiments of the present application, by providing a signal transmission path with a first bandwidth range, unwanted out-of-band high-frequency noise can be suppressed and prevented from entering the measurement device, effectively reducing noise. Furthermore, by connecting at least two signal transmission paths in parallel between the signal input and signal output terminals, and by configuring the at least two signal transmission paths with different bandwidth ranges, the bandwidth of the output signal can be differently limited or unrestricted, thereby expanding its applicability and scope of application.

[0058] In an optional embodiment, as shown in FIG4 , the signal transmission path includes a first signal transmission path TR1 configured to have a first bandwidth range;

[0059] The first signal transmission path TR1 includes a first switch module 10 connected in series between the signal input terminal and the signal output terminal;

[0060] The first switch module 10 is configured to be controlled to be opened or closed, so as to enable or disable signal transmission from the signal input end to the signal output end of the first signal transmission path TR1 .

[0061] In the embodiment of the present application, the first switch module 10 may include at least one of an operational amplifier, a semiconductor switch device, and other devices capable of implementing a switching function. In the embodiment of the present application, the first switch module is controlled to be turned on to control the conduction of signal transmission from the signal input end to the signal output end of the first signal transmission path, and the first switch module is controlled to be turned off to control the disconnection of signal transmission from the signal input end to the signal output end of the first signal transmission path, thereby achieving on-off control of the first signal transmission path.

[0062] In an optional embodiment, the first switch module 10 includes a first operational amplifier OTA1;

[0063] An input terminal of the first operational amplifier OTA1 is connected to the signal input terminal, and an output terminal of the first operational amplifier OTA1 is connected to the signal output terminal.

[0064] In an 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 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 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 amplifier. A transconductance amplifier is an amplifier with voltage input and current output. In the embodiment of the present application, noise interference from power lines and the like is reduced by using the first operational amplifier and the differential method. The use of a transconductance amplifier can also reduce distortion, offset, and thermal effects, thereby improving measurement accuracy.

[0065] In an optional embodiment, the first operational amplifier OTA1 includes a first enable control terminal configured to receive a first control signal;

[0066] The first operational amplifier OTA1 is configured to be turned on or off under the control of a first control signal.

[0067] In an embodiment of the present application, by setting a first enable control terminal, it is possible to receive a first control signal, thereby realizing control of the opening and closing of the first operational amplifier under the control of the first control signal, thereby realizing on-off control of the first signal transmission path.

[0068] As a specific example, the first enable control terminal is connected to the power supply terminal of the first operational amplifier OTA1.

[0069] In the embodiment of the present application, the first control signal received by the first enable control terminal can control the first operational amplifier OTA1 to be powered on or off, thereby realizing the control of turning the first operational amplifier OTA1 on or off. The embodiment of the present application can be used for operational amplifiers with high power consumption, which can significantly save power consumption.

[0070] As another specific example, the first enable control terminal is connected to the output terminal of the first operational amplifier OTA1.

[0071] In this embodiment of the present application, a first enable control terminal can be connected to the first signal output terminal IOP and the second signal output terminal ION of the first operational amplifier OTA1, respectively. A first control signal received by the first enable control terminal can control the output of the first operational amplifier OTA1 to be pulled high or low, ensuring that the subsequent circuit receives a fixed common-mode voltage, thereby enabling the first operational amplifier OTA1 to be turned on or off. This embodiment of the present application can rapidly turn the first operational amplifier OTA1 on and off, improving the operational amplifier's switching speed and making it suitable for low-power operational amplifiers and signal transmission paths that require fast startup.

[0072] As another specific example, the first enable control terminal is connected to the bias input terminal of the first operational amplifier OTA1.

[0073] In the embodiment of the present application, the bias input terminal of the first operational amplifier OTA1 can be an internal bias voltage input terminal or a bias current input terminal thereof, for inputting a bias voltage or a bias current into the first operational amplifier OTA1. The first control signal received by the first enable control terminal can control the loading and removal of the bias voltage or bias current, thereby controlling the turning on and off of the first operational amplifier OTA1.

[0074] In an optional embodiment, as shown in FIG4 , the first signal transmission path TR1 further includes a high-order low-pass filter 20 connected in series with the first switch module 10 ;

[0075] The high-order low-pass filter 20 is configured to have a first bandwidth range, and the first bandwidth range is adjustable.

[0076] In the embodiment of the present application, the high-order low-pass filter 20 can be connected in series between the signal input terminal (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 terminal (such as the first signal output terminal IOP and the second signal output terminal ION). By making the first bandwidth range of the high-order low-pass filter adjustable, it is possible to achieve a first signal transmission path with strong out-of-band suppression under different first bandwidth ranges, thereby achieving controllable analog front-end bandwidth and better out-of-band suppression, so that high-frequency noise is suppressed and noise performance is good. The use of a high-order low-pass filter with adjustable bandwidth can flexibly meet the different bandwidth requirements of customers, save resources, and do not require the design of multiple bandwidth restrictions.

[0077] The high-order low-pass filter 20 can be configured according to actual needs. As a specific example, the high-order low-pass filter 20 adopts a second-order transconductor-capacitor (Gm-C for short) low-pass filter, which has the advantages of lower power and higher operating frequency.

[0078] As shown in FIG5 , 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 ;

[0079] The positive input terminal and the negative input terminal of the first transconductance amplifier Gm1 are respectively configured as input signals, and the positive output terminal and the negative output terminal of the third transconductance amplifier Gm3 are respectively configured as output signals;

[0080] 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 terminal 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 terminal 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 terminal of the second capacitor C2 and the positive input terminal of the fourth transconductance amplifier Gm4, and the negative output terminal of the third transconductance amplifier Gm3 is respectively connected to the second terminal of the second capacitor C2 and the negative input terminal of the fourth transconductance amplifier Gm4.

[0081] In the embodiment of the present application, different limiting bandwidths are selected by adjusting the first capacitor and the second capacitor, thereby achieving adjustable limiting bandwidth.

[0082] In an optional embodiment, as shown in Figure 4, 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 end is output from the signal output end directly or without bandwidth restriction.

[0083] In the embodiments of the present application, the second bandwidth range can be a high bandwidth, such as the maximum signal bandwidth. Directly, the signal output from the signal output terminal can be the original signal input from the signal input terminal. Unrestricted bandwidth can be expressed as the signal output from the signal output terminal being a signal processed by at least one of amplification and first-order low-pass filtering of the signal input from the signal input terminal. By providing a second signal transmission path, the embodiments of the present application expand applicability and application scope.

[0084] In an optional embodiment, the second signal transmission path TR2 includes a second switch module 30 connected in series between the signal input end and the signal output end;

[0085] The second switch module 30 is configured to be controlled to be opened or closed, so as to enable or disable the signal transmission from the signal input end to the signal output end of the second signal transmission path TR2 .

[0086] In the embodiment of the present application, the second switch module 30 may or may not have the same structure as the first switch module 10. The second switch module 30 may include at least one of an operational amplifier, a semiconductor switch device, and other devices capable of implementing a switching function. The second switch module 30 may have the same function as the first switch module 10, namely, to implement on-off control of the second signal transmission path.

[0087] In an optional embodiment, the second switch module 30 includes a second operational amplifier OTA2;

[0088] An input terminal of the second operational amplifier OTA2 is connected to the signal input terminal, and an output terminal of the second operational amplifier OTA2 is connected to the signal output terminal.

[0089] In the embodiments of the present application, the second operational amplifier OTA2 may or may not have the same structure as the first operational amplifier OTA1. The second operational amplifier OTA2 may include two differential inputs and two differential outputs to reduce noise. The second operational amplifier OTA2 may be a differential amplifier, a transconductance amplifier, or other operational amplifier to reduce distortion, offset, and thermal effects, thereby improving measurement accuracy.

[0090] In the embodiment of the present application, the second operational amplifier OTA2 can be turned on and off in the same manner as the first operational amplifier OTA1. Specifically, the second operational amplifier OTA2 includes a second enable control terminal configured to receive a second control signal; the second operational amplifier OTA2 is configured to be turned on or off under the control of the second control signal.

[0091] As a specific example, the second enable control terminal is connected to the power supply terminal of the second operational amplifier OTA2, so that it can be used for an operational amplifier with relatively high power consumption, which can significantly save power consumption.

[0092] As another specific example, the second enable control terminal is connected to the output terminal of the second operational amplifier OTA2, so that it can be used for a low-power operational amplifier and a signal transmission path that requires fast startup.

[0093] As another specific example, the second enable control terminal is connected to the bias input terminal of the second operational amplifier OTA2 to control the opening and closing of the first operational amplifier OTA1.

[0094] In an 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 period of the other, that is, the first signal transmission path TR1 is configured to be disconnected during the conduction period of the second signal transmission path TR2, and the second signal transmission path TR2 is configured to be disconnected during the conduction period 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 turned on and the second signal transmission path TR2 is disconnected. The signal can only pass through the high-order low-pass filter 20 and the first operational amplifier OTA1 to the signal output end. In this way, the signal bandwidth of the bandwidth limiting 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. Unwanted high-frequency noise will be suppressed, thereby improving 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 connected. The signal can only pass through the second operational amplifier OTA2 to reach the signal output end. In this way, the signal bandwidth of the bandwidth limiting circuit is determined by the second signal transmission path TR2.

[0095] The embodiment of the present application also provides a front-end circuit that can be applied to instruments such as oscilloscopes and signal sources. As shown in FIG6 , the front-end circuit 001 includes a control processing module 200 and the above-mentioned bandwidth limiting circuit 100;

[0096] The control processing module 200 is configured to output a control signal to the bandwidth limiting circuit 100 to enable any one of the at least two signal transmission paths of the bandwidth limiting circuit 100 to be turned on while the other signal transmission paths are turned off.

[0097] In the embodiment of the present application, the control processing module 200 can output a control word to the first enable control terminal of the first operational amplifier OTA1 of the first signal transmission path TR1 and the second enable control terminal of the second operational amplifier OTA2 of the second signal transmission path TR2 via a register, so as to enable the first operational amplifier OTA1 and disable the second operational amplifier OTA2, or disable the first operational amplifier OTA1 and enable the second operational amplifier OTA2, thereby adjusting and controlling the bandwidth limitation of the bandwidth limiting circuit 100. Furthermore, the use of registers improves control speed.

[0098] It should be noted that the various technical features in the technical solutions described in the embodiments of the present application can be combined arbitrarily without conflict.

[0099] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementations included in the claims. Various modifications and changes can be made to the above embodiments without departing from the scope of the embodiments of the present disclosure. Similarly, the various technical features of the above embodiments can be arbitrarily combined to form other embodiments of the present application that may not be explicitly described. Therefore, the above embodiments only express several implementations of the present application and do not limit the scope of protection of the patent application.

Claims

1. A bandwidth limiting circuit, the bandwidth limiting circuit comprising at least two signal transmission paths connected in parallel between a signal input end and a signal output end; At least two signal transmission paths are configured to have different bandwidth ranges; the bandwidth ranges include 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 at least two signal transmission paths is turned on while the other one is turned off.

2. The bandwidth limiting circuit according to claim 1, wherein: The signal transmission path includes a first signal transmission path 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 opened or closed so as to enable or disconnect the signal transmission from the signal input end to the signal output end of the first signal transmission path.

3. The bandwidth limiting circuit according to claim 2, wherein: The first switch module includes a first operational amplifier; The input terminal of the first operational amplifier is connected to the signal input terminal, and the output terminal of the first operational amplifier is connected to the signal output terminal.

4. The bandwidth limiting circuit according to claim 3, wherein: The first operational amplifier comprises a first enable control terminal 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, wherein: The first enable control terminal is connected to at least one of a power supply terminal, an output terminal and a bias input terminal of the first operational amplifier.

6. The bandwidth limiting circuit according to claim 2, wherein: 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, wherein: The high-order low-pass filter comprises 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 terminal and the negative input terminal of the first transconductance amplifier are respectively configured as input signals, and the positive output terminal and the negative output terminal of the third transconductance amplifier are respectively configured as output signals; 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 terminal 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 terminal 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 terminal of the second capacitor and the positive input terminal of the fourth transconductance amplifier, and the negative output terminal of the third transconductance amplifier is respectively connected to the second terminal of the second capacitor and the positive output terminal of the fourth transconductance amplifier. The negative input of the quad transconductance amplifier is connected.

8. The bandwidth limiting circuit according to any one of claims 1 to 7, wherein: The signal transmission path includes a second signal transmission path configured to have a second bandwidth range, so that a signal transmitted through the second signal transmission path and input from the signal input end is output from the signal output end directly or without bandwidth limitation.

9. The bandwidth limiting circuit according to claim 8, wherein: 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 switch module is configured to be controlled to be opened or closed so as to enable 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, wherein: The second switch module includes a second operational amplifier; An input terminal of the second operational amplifier is connected to the signal input terminal, and an output terminal of the second operational amplifier is connected to the signal output terminal.

11. The bandwidth limiting circuit according to claim 10, wherein: The second operational amplifier comprises a second enable control terminal configured to receive a second control signal; The second operational amplifier is configured to be turned on or off under the control of the second control signal.

12. The bandwidth limiting circuit according to claim 11, wherein: The second enable control terminal is connected to at least one terminal of the second operational amplifier including a power supply terminal, an output terminal and a bias input terminal.

13. A front-end circuit, comprising a control processing module and a bandwidth limiting circuit according to any one of claims 1 to 12; The control processing module is configured to output a control signal to the bandwidth limiting circuit to enable any one of at least two signal transmission paths of the bandwidth limiting circuit to be turned on while the other paths are turned off.

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