High suppression anti-aliasing filter and test machine

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By designing an anti-aliasing filter with high rejection system, using the op amp module and impedance conversion filter module, the problem of low rejection system of the existing filter is solved, and the high rejection system and large driving capability is achieved while supporting AC and DC modes.

CN222750407UActive Publication Date: 2025-04-11HANGZHOU CHANGCHUAN TECH CO LTD

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Patent Information

Application Number: CN202420744835.7
Authority / Receiving Office: CN · China
Patent Type: Utility models(China)
Current Assignee / Owner
Filing Date: 2024-04-10
Publication Date: 2025-04-11
Estimated Expiration: 2034-04-10

AI Technical Summary

Technical Problem

In existing semiconductor tests, the suppression system of conventional filters is low, making it difficult to support both AC and DC modes, and cannot meet actual needs.

Method used

An anti-aliasing filter with high rejection system is designed, using a first-stage op amp module, an impedance conversion filter module and a multi-parallel op amp unit to achieve high rejection system and large-range current driving capabilities through impedance conversion and multi-stage filter components.

Benefits of technology

Achieve high rejection (80db) and wide range current driving capabilities, while supporting AC and DC modes, improving signal flatness, response time and reducing phase shift.

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Abstract

The present application relates to an anti-aliasing filter and a test machine with high suppression degree, wherein the filter comprises: a first-stage operational amplifier module, which is connected to a first analog signal, amplifies the first analog signal and outputs it; an impedance conversion filter module, which is connected to the first-stage operational amplifier module, performs impedance conversion and filtering on the signal output by the first-stage operational amplifier module and outputs it; a second-stage operational amplifier module, which comprises a plurality of parallel operational amplifier units, each of which is connected to a second analog signal and is connected to the impedance conversion filter module; each operational amplifier unit receives the signal output by the impedance conversion filter module and the second analog signal for signal processing, and outputs the processed analog signal. By adopting the architecture of impedance conversion filtering and multiple parallel operational amplifier units, the driving capability can be improved while achieving high suppression degree.

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Description

Technical Field

[0001] The present application relates to the field of semiconductor testing technology, and in particular to an anti-aliasing filter with high suppression and a testing machine. Background Art

[0002] Semiconductor automated testing refers to the use of automatic test equipment (ATE) to test various parameters of the device under test (DUT) to eliminate defective products and control the factory quality of semiconductor devices. Filters are often used in testers for signal suppression, but conventional filters are designed with standard 50 ohm input and output impedance, with low suppression, which is difficult to meet actual needs and cannot support both AC and DC modes. How to achieve higher suppression of filters is an urgent problem to be solved. Utility Model Content

[0003] Based on this, it is necessary to provide an anti-aliasing filter and a test machine with high suppression to address the above problems.

[0004] The first aspect of the present application provides a high-suppression anti-aliasing filter, comprising:

[0005] The first stage operational amplifier module receives the first analog signal, amplifies the first analog signal and then outputs it;

[0006] An impedance transformation and filtering module, connected to the first-stage operational amplifier module, performs impedance transformation and filtering on the signal output by the first-stage operational amplifier module and then outputs the signal;

[0007] The second-stage operational amplifier module includes multiple parallel operational amplifier units, each of which is connected to the second analog signal and is connected to the impedance transformation filter module; each operational amplifier unit receives the signal output by the impedance transformation filter module and the second analog signal for signal processing, and outputs the processed analog signal.

[0008] In one embodiment, the first-stage operational amplifier module includes an amplifier U1, a resistor R1 and a resistor R2, the non-inverting input terminal of the amplifier U1 is connected to the first analog signal, the inverting input terminal of the amplifier U1 is connected to the first end of the resistor R1 and the first end of the resistor R2, the second end of the resistor R1 is grounded, the second end of the resistor R2 is connected to the output end of the amplifier U1, and the output end of the amplifier U1 is connected to the impedance transformation filter module.

[0009] In one embodiment, the impedance transformation filtering module includes an impedance transformation unit and a multi-stage filtering component, the impedance transformation unit is connected to the first-stage operational amplifier module and the multi-stage filtering component, and the multi-stage filtering component is connected to each of the operational amplifier units.

[0010] In one embodiment, the impedance transformation unit includes a resistor R3, a resistor R4 and a capacitor C1, the first end of the resistor R3 is connected to the first-stage operational amplifier module and the first end of the capacitor C1, the second end of the resistor R3 is connected to the multi-stage filtering component, the second end of the capacitor C1 is connected to the first end of the resistor R4, and the second end of the resistor R4 is connected to the second end of the resistor R3.

[0011] In one embodiment, the multi-stage filter component includes an inductor L1, an inductor L2, an inductor L3, an inductor L4, a capacitor C2, a capacitor C3, a capacitor C4 and a capacitor C5;

[0012] The first end of the inductor L1 is connected to the impedance transformation unit, the second end of the inductor L1 is connected to the first end of the inductor L2, the second end of the inductor L2 is connected to the first end of the inductor L3, the second end of the inductor L3 is connected to the first end of the inductor L4, and the second end of the inductor L4 is connected to each of the operational amplifier units; the first end of the capacitor C2 is connected to the second end of the inductor L1, the second end of the capacitor C2 is grounded, the first end of the capacitor C3 is connected to the second end of the inductor L1, and the second end of the capacitor C3 is grounded; the first end of the capacitor C4 is connected to the second end of the inductor L3, the second end of the capacitor C4 is grounded, the first end of the capacitor C5 is connected to the second end of the inductor L3, and the second end of the capacitor C5 is grounded.

[0013] In one embodiment, the impedance transformation filtering module further includes a resistor R5, a first end of the resistor R5 is connected to the second end of the inductor L4, and a second end of the resistor R5 is grounded.

[0014] In one embodiment, the operational amplifier unit includes a first operational amplifier unit and a second operational amplifier unit; the first operational amplifier unit is connected to the multi-stage filtering component and is connected to the second analog signal; the second operational amplifier unit is connected to the multi-stage filtering component and is connected to the second analog signal.

[0015] In one embodiment, the first operational amplifier unit includes an amplifier U2, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R15 and a resistor R17, the in-phase input terminal of the amplifier U2 is connected to the first end of the resistor R7, the inverting input terminal of the amplifier U2 is connected to the first end of the resistor R6, the second end of the resistor R7 is connected to the multi-stage filtering component, the second end of the resistor R6 is connected to the second analog signal, the first end of the resistor R17 is connected to the first end of the resistor R6, and the second end of the resistor R17 is connected to the second end of the resistor R6; the resistor R8 is connected in parallel with the resistor R9, one end of which is connected to the inverting input terminal of the amplifier U2, and the other end is connected to the output terminal of the amplifier U2; the first end of the resistor R15 is connected to the output terminal of the amplifier U2, and the second end of the resistor R15 is connected to the second operational amplifier unit.

[0016] In one embodiment, the second operational amplifier unit includes an amplifier U3, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14 and a resistor R16, the in-phase input terminal of the amplifier U3 is connected to the first end of the resistor R12, the inverting input terminal of the amplifier U2 is connected to the first end of the resistor R11, the second end of the resistor R12 is connected to the multi-stage filtering component, the second end of the resistor R11 is connected to the second analog signal, the first end of the resistor R10 is connected to the first end of the resistor R11, and the second end of the resistor R10 is connected to the second end of the resistor R11; the resistor R13 is connected in parallel with the resistor R14, one end of which is connected to the inverting input terminal of the amplifier U3, and the other end is connected to the output terminal of the amplifier U3; the first end of the resistor R16 is connected to the output terminal of the amplifier U3, and the second end of the resistor R16 is connected to the first operational amplifier unit.

[0017] A second aspect of the present application provides a test machine, comprising the above-mentioned high-suppression anti-aliasing filter.

[0018] In the above-mentioned high-suppression anti-aliasing filter and test machine, the first-stage operational amplifier module amplifies the first analog signal and then outputs it, and the impedance conversion filter module performs impedance conversion and filtering on the signal output by the first-stage operational amplifier module and then outputs it. The second-stage operational amplifier module includes a plurality of parallel operational amplifier units, each of which receives the signal output by the impedance conversion filter module and the second analog signal for signal processing, and outputs the processed analog signal. By adopting the architecture of impedance conversion filtering and multiple parallel operational amplifier units, the driving capability can be improved while achieving high suppression, and both AC and DC modes can be supported at the same time, with high suppression of AC signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1is a structural block diagram of an anti-aliasing filter with high suppression in one embodiment;

[0020] Figure 2 is a structural schematic diagram of a first-stage operational amplifier module in an embodiment;

[0021] Figure 3 A structural schematic diagram of an impedance transformation filter module in an embodiment;

[0022] Figure 4 A schematic diagram of the performance of an adjustable input and output impedance filter in one embodiment;

[0023] Figure 5 FIG. 4 is a structural schematic diagram of a second-stage operational amplifier module in an embodiment. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0026] It is understood that the terms "first", "second", etc. used in this application can be used to describe various elements in this article, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. The "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if the connected circuits, modules, units, etc. have transmission of electrical signals or data with each other.

[0027] When used herein, the singular forms "a", "an", and "the" may also include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0028] In one embodiment, Figure 1As shown, a high-suppression anti-aliasing filter is provided, including a first-stage operational amplifier module 110, an impedance transformation filter module 120 and a second-stage operational amplifier module 130, wherein the impedance transformation filter module 120 is connected to the first-stage operational amplifier module 110, and the second-stage operational amplifier module 130 includes a plurality of parallel operational amplifier units, each of which is connected to the second analog signal and connected to the impedance transformation filter module 120. The first-stage operational amplifier module 110 is connected to the first analog signal, amplifies the first analog signal and outputs it, and the impedance transformation filter module 120 performs impedance transformation and filtering on the signal output by the first-stage operational amplifier module 110 and outputs it. Each operational amplifier unit receives the signal output by the impedance transformation filter module 120 and the second analog signal for signal processing, and outputs the processed analog signal.

[0029] Specifically, the first stage operational amplifier module 110 is used as the pre-stage circuit of the filter, amplifies the input first analog signal to provide a certain gain, and then performs impedance transformation and signal filtering through the impedance transformation filter module 120, and the second stage operational amplifier module 130 is used as the post-stage circuit of the filter, wherein the operational amplifier unit arranged in parallel amplifies or adds the accessed signal and outputs the processed analog signal. The number of operational amplifier units can be two or more, and can be adjusted based on the demand for driving capability. Each operational amplifier unit includes two input terminals and an output terminal, wherein one input terminal is connected to the impedance transformation filter module 120, and the other input terminal is connected to the second analog signal, and the output terminals of each operational amplifier unit are connected to each other as the output terminals of the anti-aliasing filter, and the processed analog signal is output, which can simultaneously meet the signal output and filtering of the single-ended and differential modes. The architecture of impedance transformation filtering and multiple parallel operational amplifier units can achieve a wide range of current driving capability while achieving high suppression (80db), and the flatness, response time and phase shift of the filter are improved.

[0030] In one embodiment, Figure 2 As shown, the first-stage operational amplifier module 110 includes an amplifier U1, a resistor R1 and a resistor R2, the in-phase input terminal IN+ of the amplifier U1 is connected to the first analog signal, the inverting input terminal IN- of the amplifier U1 is connected to the first end of the resistor R1 and the first end of the resistor R2, the second end of the resistor R1 is grounded, the second end of the resistor R2 is connected to the output end of the amplifier U1, and the output end of the amplifier U1 is connected to the impedance conversion filter module 120. Among them, the signal A represents the first analog signal connected, and the in-phase input terminal IN+ of the amplifier U1 can also be provided with a 100 ohm resistor, through which the first analog signal is connected. The amplifier U1 is a in-phase proportional operational amplifier, which amplifies the input first analog signal, provides a certain gain, and changes the input impedance of the signal.

[0031] like Figure 3As shown, the impedance transformation filter module 120 includes an impedance transformation unit 122 and a multi-stage filter component 124. The impedance transformation unit 122 is connected to the first-stage operational amplifier module 110 and the multi-stage filter component 124. The multi-stage filter component 124 is connected to each operational amplifier unit. Among them, the signal A' represents the signal output by the first-stage operational amplifier module 110. The impedance transformation unit 122 performs impedance transformation on the signal A', and then performs multi-stage low-pass filtering on the signal through the multi-stage filter component 124, and outputs the signal A" to each operational amplifier unit.

[0032] Continue to refer to Figure 3 The impedance transformation unit 122 includes a resistor R3, a resistor R4 and a capacitor C1, a first end of the resistor R3 is connected to the first-stage operational amplifier module 110 and the first end of the capacitor C1, a second end of the resistor R3 is connected to the multi-stage filtering component 124, a second end of the capacitor C1 is connected to the first end of the resistor R4, and a second end of the resistor R4 is connected to the second end of the resistor R3. Further, the multi-stage filtering component 124 includes an inductor L1, an inductor L2, an inductor L3, an inductor L4, a capacitor C2, a capacitor C3, a capacitor C4 and a capacitor C5; a first end of the inductor L1 is connected to the impedance transformation unit 122, a second end of the inductor L1 is connected to a first end of the inductor L2, a second end of the inductor L2 is connected to a first end of the inductor L3, a second end of the inductor L3 is connected to a first end of the inductor L4, and a second end of the inductor L4 is connected to each operational amplifier unit; a first end of the capacitor C2 is connected to a second end of the inductor L1, a second end of the capacitor C2 is grounded, a first end of the capacitor C3 is connected to a second end of the inductor L1, and a second end of the capacitor C3 is grounded; a first end of the capacitor C4 is connected to a second end of the inductor L3, a second end of the capacitor C4 is grounded, a first end of the capacitor C5 is connected to a second end of the inductor L3, and a second end of the capacitor C5 is grounded.

[0033] Specifically, the first end of the resistor R3 is connected to the output end of the amplifier U1 in the first-stage operational amplifier module 110. The first end of the inductor L1 is connected to the second end of the resistor R3 in the impedance transformation unit 122. In the impedance transformation unit 122, the output resistance of the operational amplifier is adjusted by the resistor R3, and the signal is low-pass filtered by the capacitor C1 and the resistor R4. The signal after impedance transformation is subjected to multi-stage low-pass filtering in the multi-stage filtering component 124, and the signal A" after filtering is transmitted to each operational amplifier unit. In addition, the impedance transformation filter module 120 also includes a resistor R5, the first end of the resistor R5 is connected to the second end of the inductor L4, and the second end of the resistor R5 is grounded. The impedance of the subsequent operational amplifier can be matched by adjusting the resistance value of R5. Figure 4 This is a performance diagram of an adjustable input and output impedance filter. By adjusting the resistance values of resistors R3 and R5, the impedances of the filter's front-stage circuit and rear-stage circuit can be well matched.

[0034] In one embodiment, Figure 5As shown, the operational amplifier unit includes a first operational amplifier unit 132 and a second operational amplifier unit 134; the first operational amplifier unit 132 is connected to the multi-stage filtering component 124 and is connected to the second analog signal; the second operational amplifier unit 134 is connected to the multi-stage filtering component 124 and is connected to the second analog signal.

[0035] Among them, signal B represents the second analog signal, and signal C represents the analog signal output by the filter. The first operational amplifier unit 132 may specifically include an amplifier U2, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R15, and a resistor R17, wherein the in-phase input terminal IN+ of the amplifier U2 is connected to the first end of the resistor R7, the inverting input terminal IN- of the amplifier U2 is connected to the first end of the resistor R6, the second end of the resistor R7 is connected to the multi-stage filter component 124, the second end of the resistor R6 is connected to the second analog signal, and the resistor R17 is connected in parallel with the resistor R6; after the resistor R8 is connected in parallel with the resistor R9, one end is connected to the inverting input terminal IN- of the amplifier U2, and the other end is connected to the output end of the amplifier U2; the first end of the resistor R15 is connected to the output end of the amplifier U2, and the second end of the resistor R15 is connected to the second operational amplifier unit 134.

[0036] The second operational amplifier unit 134 may specifically include an amplifier U3, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14 and a resistor R16. The in-phase input terminal IN+ of the amplifier U3 is connected to the first end of the resistor R12, the inverting input terminal IN- of the amplifier U2 is connected to the first end of the resistor R11, the second end of the resistor R12 is connected to the multi-stage filter component 124, the second end of the resistor R11 is connected to the second analog signal, and the resistor R10 and the resistor R11 are connected in parallel; after the resistor R13 and the resistor R14 are connected in parallel, one end is connected to the inverting input terminal IN- of the amplifier U3, and the other end is connected to the output end of the amplifier U3; the first end of the resistor R16 is connected to the output end of the amplifier U3, and the second end of the resistor R16 is connected to the first operational amplifier unit 132.

[0037] Specifically, amplifier U2 and amplifier U3 are both in-phase proportional operational amplifiers, and the second end of resistor R7 and the second end of resistor R12 are connected to the second end of inductor L4 in multi-stage filter component 124. The second end of resistor R15 serves as the output end of the first operational amplifier unit 132, and the second end of resistor R16 serves as the output end of the second operational amplifier unit 134. The second end of resistor R16 is connected to the second end of resistor R15. Signal A" filtered by multi-stage filter component 124 ， The signal is amplified or added by amplifiers U2 and U3, and the processed signal is transformed into output impedance by resistors R15 and R16 respectively to achieve the required output impedance.

[0038] In one embodiment, a test machine is also provided, including the above-mentioned high-suppression anti-aliasing filter. The test machine can be a digital test machine or other types of test machines.

[0039] The above-mentioned high-suppression anti-aliasing filter and tester can achieve 80db suppression of 0Hz-100MHz wideband signal out-band and large current output (0-1A), and have excellent performance in signal flatness, and the transition band is 1 times the bandwidth, which is a very outstanding performance among existing products. The filter and tester have the following advantages:

[0040] 1. High suppression, capable of 80db suppression capability, which is very popular in applications with increasingly higher filtering performance. It can achieve filtering of large and small signals at the same time, which is indispensable in the design of automation equipment.

[0041] 2. High driving capability. While achieving high suppression, it can increase the driving capability exponentially by increasing the number of operational amplifiers in parallel, which is indispensable in high-power applications.

[0042] 3. Signal phase shift is reduced. Since the number of filter stages is relatively small, the impact on the signal phase is small, and the phase shift index is optimized to a certain extent.

[0043] 4. The response time of the signal is reduced. Due to fewer cascades, the number of modules the signal passes through is reduced, the response time of the signal is reduced, the output delay of the signal is reduced, and the uncertainty of the delay is also reduced.

[0044] 5. Adjustable input and output impedance greatly improves the application of the filter.

[0045] 6. It is composed of resistors, capacitors, inductors and ordinary operational amplifiers, which reduces the cost of filters and testers.

[0046] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0047] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the utility model patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A high-suppression anti-aliasing filter, characterized in that: include: The first stage operational amplifier module receives the first analog signal, amplifies the first analog signal and then outputs it; An impedance transformation and filtering module, connected to the first-stage operational amplifier module, performs impedance transformation and filtering on the signal output by the first-stage operational amplifier module and then outputs the signal; The second-stage operational amplifier module includes multiple parallel operational amplifier units, each of which is connected to the second analog signal and is connected to the impedance transformation filter module; each operational amplifier unit receives the signal output by the impedance transformation filter module and the second analog signal for signal processing, and outputs the processed analog signal.

2. The anti-aliasing filter according to claim 1, characterized in that The first-stage operational amplifier module includes an amplifier U1, a resistor R1 and a resistor R2. The in-phase input terminal of the amplifier U1 is connected to the first analog signal, the inverting input terminal of the amplifier U1 is connected to the first end of the resistor R1 and the first end of the resistor R2, the second end of the resistor R1 is grounded, the second end of the resistor R2 is connected to the output end of the amplifier U1, and the output end of the amplifier U1 is connected to the impedance transformation filter module.

3. The anti-aliasing filter according to claim 1, characterized in that The impedance transformation filtering module comprises an impedance transformation unit and a multi-stage filtering component. The impedance transformation unit is connected to the first-stage operational amplifier module and the multi-stage filtering component. The multi-stage filtering component is connected to each of the operational amplifier units.

4. The anti-aliasing filter according to claim 3, characterized in that The impedance transformation unit includes a resistor R3, a resistor R4 and a capacitor C1, the first end of the resistor R3 is connected to the first-stage operational amplifier module and the first end of the capacitor C1, the second end of the resistor R3 is connected to the multi-stage filtering component, the second end of the capacitor C1 is connected to the first end of the resistor R4, and the second end of the resistor R4 is connected to the second end of the resistor R3.

5. The anti-aliasing filter according to claim 3, characterized in that: The multi-stage filter component includes an inductor L1, an inductor L2, an inductor L3, an inductor L4, a capacitor C2, a capacitor C3, a capacitor C4 and a capacitor C5; The first end of the inductor L1 is connected to the impedance transformation unit, the second end of the inductor L1 is connected to the first end of the inductor L2, the second end of the inductor L2 is connected to the first end of the inductor L3, the second end of the inductor L3 is connected to the first end of the inductor L4, and the second end of the inductor L4 is connected to each of the operational amplifier units; the first end of the capacitor C2 is connected to the second end of the inductor L1, the second end of the capacitor C2 is grounded, the first end of the capacitor C3 is connected to the second end of the inductor L1, and the second end of the capacitor C3 is grounded; the first end of the capacitor C4 is connected to the second end of the inductor L3, the second end of the capacitor C4 is grounded, the first end of the capacitor C5 is connected to the second end of the inductor L3, and the second end of the capacitor C5 is grounded.

6. The anti-aliasing filter according to claim 5, characterized in that The impedance transformation filter module further includes a resistor R5, a first end of the resistor R5 is connected to the second end of the inductor L4, and a second end of the resistor R5 is grounded.

7. The anti-aliasing filter according to claim 3, characterized in that: The operational amplifier unit includes a first operational amplifier unit and a second operational amplifier unit; the first operational amplifier unit is connected to the multi-stage filtering component and is connected to the second analog signal; the second operational amplifier unit is connected to the multi-stage filtering component and is connected to the second analog signal.

8. The anti-aliasing filter according to claim 7, characterized in that: The first operational amplifier unit includes an amplifier U2, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R15 and a resistor R17. The in-phase input terminal of the amplifier U2 is connected to the first end of the resistor R7, the inverting input terminal of the amplifier U2 is connected to the first end of the resistor R6, the second end of the resistor R7 is connected to the multi-stage filtering component, the second end of the resistor R6 is connected to the second analog signal, the first end of the resistor R17 is connected to the first end of the resistor R6, and the second end of the resistor R17 is connected to the second end of the resistor R6; the resistor R8 is connected in parallel with the resistor R9, and one end is connected to the inverting input terminal of the amplifier U2, and the other end is connected to the output terminal of the amplifier U2; the first end of the resistor R15 is connected to the output terminal of the amplifier U2, and the second end of the resistor R15 is connected to the second operational amplifier unit.

9. The anti-aliasing filter according to claim 7, characterized in that: The second operational amplifier unit includes an amplifier U3, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14 and a resistor R16. The in-phase input terminal of the amplifier U3 is connected to the first end of the resistor R12, the inverting input terminal of the amplifier U2 is connected to the first end of the resistor R11, the second end of the resistor R12 is connected to the multi-stage filtering component, the second end of the resistor R11 is connected to the second analog signal, the first end of the resistor R10 is connected to the first end of the resistor R11, and the second end of the resistor R10 is connected to the second end of the resistor R11; the resistor R13 is connected in parallel with the resistor R14, and one end is connected to the inverting input terminal of the amplifier U3, and the other end is connected to the output terminal of the amplifier U3; the first end of the resistor R16 is connected to the output terminal of the amplifier U3, and the second end of the resistor R16 is connected to the first operational amplifier unit.

10. A testing machine, characterized in that: An anti-aliasing filter with high suppression degree comprising the one described in any one of claims 1-9.