Device and method for testing current noise of operational amplifier

Abstract

The invention provides an operational amplifier current noise testing device and method, relates to the technical field of operational amplifier noise testing, and aims to find out the position of an introduced pole by testing an input end capacitor and compensate the influence of the pole introduced by a sampling resistor and a stray capacitor in a mathematical correction mode so as to test the noise of the operational amplifier. Therefore, the current noise characteristic of the operational amplifier can be accurately measured. The device comprises a tested device module which comprises a to-be-tested operational amplifier and a sampling resistor, and the sampling resistor is used for converting current noise of the input end of the operational amplifier into voltage noise; the auxiliary amplifier module is used for further amplifying the voltage noise; the capacitance test module is used for testing the total input capacitance of the tested device module, and the total input capacitance comprises the input capacitance of the operational amplifier and the stray capacitance introduced by the system; wherein after the total input capacitance is obtained through testing, the attenuation frequency of the noise signal is corrected according to the total input capacitance, and the corrected noise signal is obtained.

Description

Technical Field

[0001] The present disclosure relates to the technical field of operational amplifier noise testing, and more specifically, to an operational amplifier current noise testing device and method. Background Art

[0002] High-precision, low-noise operational amplifiers are widely used in the core parts of signal receiving systems and have a wide range of applications in audio, communications, and instrumentation. In practical applications, when the source impedance of the operational amplifier is high, the current noise of the operational amplifier will have a great impact on the detection accuracy of the signal. With the rapid development of integrated circuit technology, international operational amplifiers have achieved input current noise density as low as 100 fA / √Hz at 1kHz. However, the current noise of 100fA / √Hz is easily affected by environmental interference and the accuracy of the test circuit in actual testing, making it difficult to accurately measure. Therefore, it is increasingly important to study the test method of the current noise of operational amplifiers.

[0003] The conventional test method for operational amplifier current noise is to place a sampling resistor at the input of the operational amplifier and convert the current noise into voltage noise for testing. The size of the sampling resistor should be selected so that the voltage noise converted from the current noise through the sampling resistor is greater than the thermal noise of the sampling resistor itself, and much greater than the input voltage noise of the operational amplifier itself. At this time, the current noise will become the main noise source, and then the current noise that changes with frequency will be displayed by analyzing the relationship between the thermal noise of the sampling resistor and the voltage noise converted from the current noise through the sampling resistor.

[0004] However, in practical applications, when testing smaller current noise, a large sampling resistor needs to be set at the input of the amplifier to prevent the voltage noise converted from the current noise from being drowned out by the thermal noise of the sampling resistor itself. In the current noise test system, the capacitance at the input of the operational amplifier is very susceptible to the influence of stray capacitance. This will result in a lower pole being introduced into the noise test system under the combined effect of the large sampling resistor and stray capacitance, causing the measured noise to tend to attenuate at lower frequencies, making it impossible to accurately test the current noise of the operational amplifier. Summary of the invention

[0005] In view of this, the present disclosure provides an operational amplifier current noise testing device and method, which aims to find the position of the introduced pole (frequency attenuation) by testing the input capacitance, and compensate for the influence of the pole introduced by the sampling resistor and stray capacitance by mathematical correction, so as to accurately measure the current noise characteristics of the operational amplifier.

[0006] One aspect of the present disclosure provides an operational amplifier current noise test device, the device comprising: a device under test module, comprising an operational amplifier to be tested and a sampling resistor, wherein the sampling resistor is used to convert the current noise at the input end of the operational amplifier into voltage noise; an auxiliary amplifier module, used to further amplify the voltage noise; a capacitance test module, used to test the total input capacitance of the device under test module, the total input capacitance comprising the input capacitance of the operational amplifier itself, and the stray capacitance introduced by the system; wherein after the total input capacitance is obtained through the test, the attenuation frequency of the noise signal is corrected according to the total input capacitance to obtain the corrected noise signal.

[0007] According to an embodiment of the present disclosure, the sampling resistor includes: a first resistor; and a second resistor connected in parallel with the first resistor, wherein the first resistor and the second resistor are connected to form a common-mode amplifier to control the amplification factor of the device under test module.

[0008] According to an embodiment of the present disclosure, the device under test module also includes: a first switch for controlling the on-off of the operational amplifier; a second switch for adjusting the amplification factor by controlling the on-off of the first resistor; and a third switch for adjusting the amplification factor by controlling the on-off of the second resistor.

[0009] According to an embodiment of the present disclosure, the auxiliary amplifier module includes: an auxiliary amplifier; a third resistor; a fourth resistor connected in parallel with the third resistor, wherein the third resistor and the fourth resistor amplify the noise signal output by the device under test module by being connected to form a common-mode amplifier; and a fourth switch, used to adjust the amplification factor by controlling the on and off of the fourth resistor.

[0010] According to an embodiment of the present disclosure, the capacitor testing module includes: a capacitor to be measured; a fifth resistor; a sixth resistor connected in parallel with the fifth resistor, wherein the sixth resistor, the fifth resistor and the capacitor to be measured together form a resistor-capacitor loop; and a fifth switch for controlling the on-off of the resistor-capacitor loop.

[0011] According to an embodiment of the present disclosure, the total input capacitance C of the device under test module TEST for:

[0012]

[0013] Wherein, R6 represents the resistance value of the sixth resistor, and f1 represents the cut-off frequency of the system.

[0014] According to an embodiment of the present disclosure, the corrected noise signal i n for:

[0015]

[0016] Among them, V O_noiserepresents the noise signal after being amplified by the device under test module and the auxiliary amplifier module. G1 represents the amplification factor of the device under test module, G2 represents the amplification factor of the auxiliary amplifier module, and e n represents the thermal noise voltage of the sampling resistor, R S Indicates the resistance of the sampling resistor, C TEST Indicates the capacitance of the capacitor to be tested.

[0017] According to an embodiment of the present disclosure, the apparatus further includes: a power supply module, configured to provide a stable voltage to the device under test module and the auxiliary amplifier module.

[0018] According to an embodiment of the present disclosure, the power supply module includes: a low-noise power supply for providing an input voltage; and a low-noise linear regulator for adjusting the input voltage provided by the low-noise power supply to a stable output voltage to reduce the impact of voltage fluctuations on system performance.

[0019] Another aspect of the present disclosure provides a method for testing current noise of an operational amplifier, the method comprising: converting the current noise at the input end of the operational amplifier into voltage noise; further amplifying the voltage noise; testing the total input capacitance, wherein the total input capacitance includes the input capacitance of the operational amplifier itself and the stray capacitance introduced by the system; after the total input capacitance is obtained through the test, correcting the attenuation frequency of the noise signal according to the total input capacitance to obtain a corrected noise signal.

[0020] The operational amplifier current noise testing device and method provided by the embodiments of the present disclosure have at least the following beneficial effects:

[0021] (1) The operational amplifier current noise testing device and method provided in the embodiments of the present disclosure find the position of the introduced pole (frequency attenuation) by testing the input capacitance, and compensate the influence of the pole introduced by the sampling resistor and the stray capacitance by mathematical correction, so as to accurately measure the current noise characteristics of the operational amplifier.

[0022] (2) The operational amplifier current noise testing device and method provided in the embodiments of the present disclosure do not need to use expensive precision resistors and capacitors. Instead, it only needs to set up an additional input capacitance testing circuit to accurately measure the total input capacitance of the operational amplifier. The exact position of the introduced pole can be obtained based on the resistance value of the set sampling resistor and the total input capacitance. The influence of the pole can be corrected from the final noise curve to obtain accurate input current noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0024] Figure 1The structure diagram of a conventional operational amplifier current noise test circuit is schematically shown;

[0025] Figure 2 The structure diagram of the operational amplifier current noise testing device according to the embodiment of the present disclosure is schematically shown;

[0026] Figure 3 The structure diagram of the operational amplifier current noise source according to the embodiment of the present disclosure is schematically shown;

[0027] Figure 4 The directly obtained operational amplifier current noise curve is schematically shown;

[0028] Figure 5 A diagram schematically shows a current noise curve of an operational amplifier after eliminating the effect of the introduced pole;

[0029] Figure 6 The flowchart of the operational amplifier current noise testing method according to the embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0031] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0032] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0033] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0034] High-precision, low-noise operational amplifiers are widely used in the core parts of signal receiving systems and have a wide range of applications in audio, communications, and instrumentation. In practical applications, when the source impedance of the operational amplifier is high, the current noise of the operational amplifier will have a great impact on the detection accuracy of the signal. With the rapid development of integrated circuit technology, international operational amplifiers have achieved input current noise density as low as 100 fA / √Hz at 1kHz. However, the current noise of 100fA / √Hz is easily affected by environmental interference and the accuracy of the test circuit in actual testing, making it difficult to accurately measure. Therefore, it is increasingly important to study the test method of the current noise of operational amplifiers.

[0035] The conventional test method for operational amplifier current noise is to place a sampling resistor at the input of the operational amplifier and convert the current noise into voltage noise for testing. The size of the sampling resistor should be selected so that the voltage noise converted from the current noise through the sampling resistor is greater than the thermal noise of the sampling resistor itself, and much greater than the input voltage noise of the operational amplifier itself. At this time, the current noise will become the main noise source, and then the current noise that changes with frequency will be displayed by analyzing the relationship between the thermal noise of the sampling resistor and the voltage noise converted from the current noise through the sampling resistor.

[0036] However, in practical applications, when testing smaller current noise, a large sampling resistor needs to be set at the input of the amplifier so that the voltage noise converted from the current noise will not be drowned out by the thermal noise of the sampling resistor itself. In the current noise test system, the capacitance size at the input of the operational amplifier is very susceptible to the influence of stray capacitance. This will result in the introduction of a lower pole to the noise test system under the combined effect of the large sampling resistor and stray capacitance, so that the measured noise will tend to attenuate at a lower frequency, and the current noise of the operational amplifier cannot be accurately tested. For example, in the prior art, the conventional test method for current noise testing.

[0037] Figure 1 The structure of a conventional operational amplifier current noise test circuit is schematically shown.

[0038] like Figure 1 As shown, in the prior art, a conventional operational amplifier current noise test circuit places a sampling resistor at the input end of the operational amplifier, and converts the current noise into voltage noise for testing through the sampling resistor.

[0039] For example, setting the sampling resistor R S The size is:

[0040] (1)

[0041] Wherein, k represents the Boltzmann constant, which is 1.38×10-23J / K, and T represents the thermodynamic temperature.

[0042] Current noise will become the main noise source, and by analyzing the relationship between resistor thermal noise and current noise, the current noise that changes with frequency will be displayed.

[0043] The conventional method is to use high-precision, low-drift large resistors and low-leakage capacitors in the design of the test circuit, and make additional protection designs on the PCB (Printed Circuit Board) to achieve ultra-low leakage current, so that the impact of non-ideal factors such as parasitic capacitance of the test circuit can be ignored. Finally, the measured output voltage noise is equivalent to the input end to obtain the input current noise of the operational amplifier.

[0044] Analysis shows that the current conventional operational amplifier current noise test technology has the following defects:

[0045] (1) It requires a very precise low-drift, large-resistance sampling resistor, and a special additional protection design is required on the PCB to achieve ultra-low leakage current, which makes it difficult to manufacture.

[0046] (2) When the input stray capacitance is large, the sampling resistor and stray capacitance introduce a relatively low-frequency pole, and the relatively high-frequency current noise characteristics cannot be accurately obtained.

[0047] Based on this, the embodiment of the present disclosure provides an operational amplifier current noise test device, which does not need to use expensive precision resistors and capacitors. It only needs to set up an additional input capacitance test circuit to accurately measure the total input capacitance of the operational amplifier. According to the resistance value of the set sampling resistor and the total input capacitance, the exact position of the introduced pole (frequency attenuation) is obtained, and the influence of the pole is corrected from the final noise curve to obtain accurate input current noise.

[0048] The device comprises: a device under test module, comprising an operational amplifier to be tested and a sampling resistor, wherein the sampling resistor is used to convert current noise at the input end of the operational amplifier into voltage noise; an auxiliary amplifier module, used to further amplify the voltage noise; and a capacitance test module, used to test the total input capacitance of the device under test module, wherein the total input capacitance comprises the input capacitance of the operational amplifier itself and the stray capacitance introduced by the system; wherein after the total input capacitance is obtained through the test, the attenuation frequency of the noise signal is corrected according to the total input capacitance to obtain the corrected noise signal.

[0049] The operational amplifier current noise testing device provided in the embodiment of the present disclosure finds the position of the introduced pole by testing the input capacitance, and compensates for the influence of the pole introduced by the sampling resistor and the stray capacitance by mathematical correction, thereby accurately measuring the current noise characteristics of the operational amplifier.

[0050] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0051] Figure 2 The structure diagram of the operational amplifier current noise testing device according to the embodiment of the present disclosure is schematically shown.

[0052] like Figure 2 As shown, the structure of the operational amplifier current noise testing device of the embodiment of the present disclosure may include, for example: a power supply module, a device under test (DUT) module, an auxiliary amplifier module and a capacitance testing module.

[0053] The power supply module is used to provide a stable voltage V for the DUT module and the auxiliary amplifier module. CC and V EE , so that the operational amplifier can maintain normal operation during the test, and the noise introduced by the power module can be ignored.

[0054] In this embodiment, the power supply module may, for example, include: a low-noise power supply and a low-noise linear regulator, wherein the low-noise power supply is used to provide an input voltage; the low-noise linear regulator is used to adjust the input voltage provided by the low-noise power supply to a stable output voltage, thereby reducing the impact of voltage fluctuations on system performance.

[0055] The DUT module includes: an operational amplifier to be tested, sampling resistors (a first resistor R1, a second resistor R2), a first switch S1, a second switch S2 and a third switch S3.

[0056] In this embodiment, the first resistor R1 and the second resistor R2 are connected in parallel to form a sampling resistor, which is used to convert the current noise at the input end of the operational amplifier into voltage noise. The sampling resistor is equal to the parallel resistance of the first resistor R1 and the second resistor R2. The first resistor R1 and the second resistor R2 are connected to form a common-mode amplifier to control the amplification factor of the device under test module.

[0057] The first switch S1 is used to control the on-off of the operational amplifier, the second switch S2 is used to adjust the amplification factor by controlling the on-off of the first resistor, and the third switch S3 is used to adjust the amplification factor by controlling the on-off of the second resistor.

[0058] When designing the test circuit, the appropriate sampling resistor and amplification factor can be designed according to the current noise of the operational amplifier to be tested, and the sampling resistor and amplification factor can be adjusted through the second switch S2 and the third switch S3. The output signal of the DUT module can be adjusted at V O_DUT The port is tested to determine the working status of the DUT module.

[0059] The auxiliary amplifier module is used to further amplify the voltage noise so that the tiny noise signal reaches a level that can be accurately detected by the noise analyzer.

[0060] In this embodiment, the auxiliary amplifier module may include, for example: an auxiliary amplifier, a third resistor R3, a fourth resistor R4, and a fourth switch S4.

[0061] The third resistor R3 and the fourth resistor R4 are connected in parallel, and the two are connected to form a common-mode amplifier to amplify the noise signal output by the DUT module. The fourth switch S4 is used to adjust the amplification factor by controlling the on and off of the fourth resistor.

[0062] When designing the test circuit, the appropriate amplification factor of the auxiliary amplifier can be designed according to the output signal of the DUT module and the detection accuracy of the noise analyzer, and different amplification factors can be adjusted through the fourth switch S4. The output signal of the auxiliary amplifier module (the signal after the total noise at the input end is amplified by the DUT module and the auxiliary amplifier) ​​can be set at V O_noise The port is tested to determine the working status of the auxiliary amplifier module, and finally the output noise signal is detected by a noise analyzer.

[0063] The capacitance test module is used to test the total input capacitance of the device under test module. The total input capacitance includes the input capacitance of the operational amplifier itself and the stray capacitance introduced by the system.

[0064] In this embodiment, the capacitance testing module may include, for example: a capacitor to be tested, a fifth resistor R5, a sixth resistor R6 and a fifth switch S5.

[0065] The fifth resistor R5 and the sixth resistor R6 are connected in parallel, and the capacitor to be measured, the fifth resistor R5 and the sixth resistor R6 together form an RC loop (resistance-capacitance loop); the fifth switch R5 is used to control the on-off of the RC loop.

[0066] The operational amplifier current noise test device of the disclosed embodiment can be implemented based on a printed circuit board. During the test process, the operational amplifier current noise test device (current noise test circuit) and the spectrum analyzer and advanced noise analyzer required for the test are grounded together, and the operational amplifier current noise test device is placed in a noise shielding box for testing, thereby effectively reducing the impact of environmental noise on the test results.

[0067] After the total input capacitance is obtained through testing, the attenuation frequency of the noise signal is corrected according to the total input capacitance to obtain a corrected noise signal. Specifically, the exact position of the introduced pole is obtained according to the resistance value of the set sampling resistor and the total input capacitance, thereby obtaining the final noise signal.

[0068] In this embodiment, the selection principle of the sampling resistor must comply with the following constraints:

[0069] First, it is necessary to ensure that the voltage noise converted from the current noise through the sampling resistor is greater than the thermal noise of the sampling resistor, and preferably greater than 3 times the thermal noise of the resistor. In this way, the current noise of the operational amplifier accounts for the vast majority of the noise measured at the output end, and the test results are more accurate.

[0070] If the input current noise of the operational amplifier is i n , select the sampling resistor value as R S , R S The value of is the parallel value of the first resistor R1 and the second resistor R2. Then the input current noise is converted into voltage noise v after passing through the sampling resistor. n for:

[0071] (2)

[0072] The thermal noise of the sampling resistor n_R The voltage is given by the Johnson equation:

[0073] (3)

[0074] Let the converted voltage noise be greater than the thermal noise of the sampling resistor:

[0075] (4)

[0076] Then the resistance of the sampling resistor R S satisfy:

[0077] (5)

[0078] Further setting the appropriate DUT module amplification factor, the sampling resistor size at the positive input and the input current of the operational amplifier will limit the offset voltage of the operational amplifier, for example, the operational amplifier input current I b =10pA, sampling resistor R S =10GΩ, then 10pA×10GΩ=100mV. After being amplified by the DUT module, it cannot exceed the power supply voltage range to ensure that the operational amplifier is in a normal working state. This is used as a constraint condition for selecting the sampling resistor:

[0079] (6)

[0080] Where G1 represents the amplification factor of the DUT module; V CC Indicates the power supply voltage.

[0081] In the capacitance test module, when testing the operational amplifier input capacitance and stray capacitance, the operational amplifier is connected as a follower. The capacitance C to be tested TEST The resistor forms an RC loop. Since the size of the resistor is known, the total input capacitance can be accurately obtained by testing the -3dB frequency point of the circuit.

[0082] Figure 3 The structure of the operational amplifier current noise source according to the embodiment of the present disclosure is schematically shown.

[0083] like Figure 3 As shown, in the operational amplifier current noise source structure of the embodiment of the present disclosure, a sampling resistor is set at the input end of the operational amplifier. When the current noise flows through the sampling resistor, the current noise will be converted into the voltage noise shown in formula (2). The sampling resistor itself will generate a thermal noise voltage proportional to the resistance value as shown in formula (3).

[0084] The theoretical formula for the current noise of an operational amplifier is:

[0085] (7)

[0086] Among them, I b Indicates the bias current.

[0087] Assuming the current noise at 1kHz is 100fA / √Hz, the bias current I b Taking a 1nA operational amplifier as an example, the above operational amplifier current noise test environment is used.

[0088] First, determine the sampling resistor. From equation (5), we can get that the sampling resistor should be greater than 14.81MΩ, so a 20MΩ sampling resistor can be selected. Set the DUT module magnification G1 = 11 times, then the bias current I b The maximum output voltage of the DUT module caused by out_ib for:

[0089] (8)

[0090] This will keep the amplifier in normal working condition.

[0091] The first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 are closed, and the other switches are opened, so that the circuit works in the current noise test mode, the DUT module amplifies G1 times, and the auxiliary operational amplifier amplifies G2 times.

[0092] By equating the output voltage noise measured by the noise analyzer to the input terminal and removing the thermal noise component of the sampling resistor, the output current noise can be obtained as:

[0093] (9)

[0094] And you can get Figure 4 The input current noise curve is shown.

[0095] Figure 4 The directly derived operational amplifier current noise graph is schematically shown.

[0096] like Figure 4 As shown in FIG. 1 , a pole is introduced under the combined effect of the sampling resistor and the input stray capacitance, causing the current noise to begin to decrease before entering the corner frequency, and it is impossible to obtain a stable current noise at 1kHz.

[0097] In order to eliminate the influence of the pole introduced by the sampling resistor and the input stray capacitance, the third switch S3 and the fifth switch S5 are closed, the circuit is set to the total input capacitance test mode, and the input capacitance of the operational amplifier is tested. The fifth resistor R5 can be set to 50Ω, the sixth resistor R6 can be set to 1MΩ, the operational amplifier can be connected to the follower state, and the network analyzer and the power separator can be used for testing. I_SIG The input signal at V O_SIG The signal is detected at the end, and the -3dB frequency f1 is read out in the test results of the network analyzer. The total input capacitance of the operational amplifier is:

[0098] (10)

[0099] Wherein, R6 represents the resistance value of the sixth resistor, and f1 represents the cut-off frequency of the system.

[0100] The current noise of the operational amplifier is corrected to eliminate the influence of the poles introduced by the sampling resistor and stray capacitance. The corrected noise signal i n for:

[0101] (11)

[0102] Among them, V O_noise represents the noise signal after being amplified by the device under test module and the auxiliary amplifier module. G1 represents the amplification factor of the device under test module, G2 represents the amplification factor of the auxiliary amplifier module, and e n represents the thermal noise voltage of the sampling resistor, R S Indicates the resistance of the sampling resistor, C TEST Indicates the capacitance of the capacitor to be tested.

[0103] Similarly, the current noise curve after correcting the poles introduced by the sampling resistor and stray capacitance can be obtained, such as Figure 5 shown.

[0104] Figure 5 The diagram schematically shows a current noise curve of an operational amplifier after eliminating the effect of the introduced pole.

[0105] like Figure 5 As shown, the operational amplifier current noise testing device provided by the embodiment of the present disclosure effectively solves the non-ideal factors caused by the large sampling resistor and input stray capacitance.

[0106] The operational amplifier current noise test device provided by the embodiment of the present disclosure does not need to use expensive precision resistors and capacitors. It only needs to set up an additional input capacitance test circuit to accurately measure the total input capacitance of the operational amplifier. According to the resistance value of the set sampling resistor and the total input capacitance, the exact position of the introduced pole is obtained, and the influence of the pole is corrected from the final noise curve, thereby obtaining accurate input current noise.

[0107] Another aspect of the disclosed embodiment further provides a method for testing current noise of an operational amplifier. Figure 6 shown.

[0108] Figure 6 The flowchart of the operational amplifier current noise testing method according to the embodiment of the present disclosure is schematically shown.

[0109] like Figure 6 As shown, the operational amplifier current noise testing method according to the embodiment of the present disclosure includes:

[0110] S1, uses the device under test module to convert the current noise at the input of the operational amplifier into voltage noise.

[0111] S2, uses an auxiliary amplifier module to further amplify the voltage noise.

[0112] S3, using a capacitance test module to test the total input capacitance, wherein the total input capacitance includes the input capacitance of the operational amplifier itself and the stray capacitance introduced by the system.

[0113] S4, after the total input capacitance is obtained through testing, the attenuation frequency of the noise signal is corrected according to the total input capacitance to obtain a corrected noise signal.

[0114] The flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram may represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of the code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box may also occur in an order different from that marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart, can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions. It can be understood by those skilled in the art that the features recorded in the various embodiments of the present disclosure can be combined and / or combined in a variety of ways, even if such a combination or combination is not explicitly recorded in the present disclosure. In particular, without departing from the spirit and teaching of the present disclosure, the features described in the various embodiments of the present disclosure may be combined and / or combined in a variety of ways. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0115] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. An operational amplifier current noise test device, characterized in that: The device comprises: The device under test module comprises an operational amplifier to be tested and a sampling resistor, wherein the sampling resistor is used to convert the current noise at the input end of the operational amplifier into voltage noise; An auxiliary amplifier module, used to further amplify the voltage noise; A capacitance test module, used to test the total input capacitance of the device under test module, wherein the total input capacitance includes the input capacitance of the operational amplifier itself and the stray capacitance introduced by the system; After the total input capacitance is obtained through testing, the attenuation frequency of the noise signal is corrected according to the total input capacitance to obtain a corrected noise signal.

2. The device according to claim 1, characterized in that The sampling resistor comprises: a first resistor; A second resistor is connected in parallel with the first resistor, wherein the first resistor and the second resistor are connected to form a common-mode amplifier to control the amplification factor of the device under test module.

3. The device according to claim 2, characterized in that The device under test module also includes: A first switch, used to control the on / off of the operational amplifier; A second switch, used to adjust the amplification factor by controlling the on / off of the first resistor; The third switch is used to adjust the amplification factor by controlling the on-off of the second resistor.

4. The device according to claim 1, characterized in that The auxiliary amplifier module comprises: Auxiliary amplifier; The third resistor; a fourth resistor connected in parallel with the third resistor, wherein the third resistor and the fourth resistor are connected to form a common-mode amplifier to amplify the noise signal output by the device under test module; The fourth switch is used to adjust the amplification factor by controlling the on-off of the fourth resistor.

5. The device according to claim 1, characterized in that The capacitance test module comprises: Capacitor to be tested; a fifth resistor; a sixth resistor connected in parallel with the fifth resistor, wherein the sixth resistor, the fifth resistor and the capacitor to be measured together form a resistor-capacitor loop; The fifth switch is used to control the on-off of the resistor-capacitor loop.

6. The device according to claim 5, characterized in that The total input capacitance C of the DUT module TEST for: Wherein, R6 represents the resistance value of the sixth resistor, and f1 represents the cut-off frequency of the system.

7. The device according to claim 6, characterized in that The corrected noise signal i n for: Among them, V O_noise represents the noise signal after being amplified by the device under test module and the auxiliary amplifier module. G1 represents the amplification factor of the device under test module, G2 represents the amplification factor of the auxiliary amplifier module, and e n represents the thermal noise voltage of the sampling resistor, R S Indicates the resistance of the sampling resistor, C TEST Indicates the capacitance of the capacitor to be tested.

8. The device according to claim 1, characterized in that The device also includes: A power supply module is used to provide a stable voltage for the device under test module and the auxiliary amplifier module.

9. The device according to claim 8, characterized in that The power module comprises: A low noise power supply for providing input voltage; The low-noise linear regulator is used to adjust the input voltage provided by the low-noise power supply to a stable output voltage, thereby reducing the impact of voltage fluctuations on system performance.

10. A method for testing current noise of an operational amplifier, characterized in that: The method comprises: Convert current noise at the op amp input to voltage noise; further amplifying the voltage noise; Testing the total input capacitance, wherein the total input capacitance includes the input capacitance of the operational amplifier itself and the stray capacitance introduced by the system; After the total input capacitance is obtained through testing, the attenuation frequency of the noise signal is corrected according to the total input capacitance to obtain a corrected noise signal.

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