Operational amplifier current noise testing apparatus and method

Abstract

The present disclosure provides an operational amplifier current noise testing device and method, relates to the technical field of operational amplifier noise testing, aims to find the position of the introduced pole by testing the input end capacitor, and compensate the influence of the introduced pole of the sampling resistance and stray capacitor through the mathematical correction method, so as to accurately measure the current noise characteristics of the operational amplifier. 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 the current noise at the input end of the operational amplifier into voltage noise; an auxiliary amplifier module for further amplifying the voltage noise; a capacitor testing module for testing 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, the attenuation frequency of the noise signal is corrected according to the total input capacitance to obtain the corrected noise signal.

Description

Technical Field

[0001] This disclosure relates to the field of operational amplifier noise testing technology, and more specifically, to an operational amplifier current noise testing device and method. Background Technology

[0002] High-precision, low-noise operational amplifiers are widely used in the core components of signal receiving systems, finding broad applications in audio, communication, and instrumentation. In practical applications, when the source impedance of the operational amplifier is high, its current noise significantly impacts signal detection accuracy. With the rapid development of integrated circuit technology, internationally available operational amplifiers have achieved input current noise densities as low as 100 fA / √Hz at 1kHz. However, current noise levels of 100 fA / √Hz are easily affected by environmental interference and the precision of the test circuit, making accurate measurement difficult in actual testing. Therefore, researching testing methods for operational amplifier current noise is of increasing importance.

[0003] The conventional method for testing operational amplifier current noise is to place a sampling resistor at the input of the operational amplifier to convert the current noise into voltage noise for testing. The size of the sampling resistor should be selected such 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. In this case, the current noise becomes the main noise source. 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, the current noise that varies with frequency can be displayed.

[0004] However, in practical applications, when testing relatively small current noise, a large sampling resistor is required at the amplifier input to prevent the voltage noise converted from the current noise from being drowned out by the thermal noise of the sampling resistor itself. In current noise testing systems, the capacitance at the operational amplifier input is highly susceptible to stray capacitance. This results in a low peak in the noise testing system due to the combined effect of the large sampling resistor and stray capacitance, causing the measured noise to attenuate at lower frequencies, making it impossible to accurately measure the current noise of the operational amplifier. Summary of the Invention

[0005] In view of this, this disclosure provides an operational amplifier current noise testing device and method, which aims to find the location of the introduced poles (frequency attenuation) by testing the input capacitance, and to compensate for the influence of the poles introduced by the sampling resistor and stray capacitance through mathematical correction, thereby accurately measuring the current noise characteristics of the operational amplifier.

[0006] One aspect of this disclosure provides an operational amplifier current noise testing apparatus, comprising: a device under test module including the operational amplifier under test and a sampling resistor, wherein the sampling resistor is used to convert current noise at the input of the operational amplifier into voltage noise; an auxiliary amplifier module for further amplifying the voltage noise; and a capacitance testing module for testing the total input capacitance of the device under test module, the total input capacitance including the input capacitance of the operational amplifier itself and stray capacitance introduced by the system; wherein, after obtaining the total input capacitance, the attenuation frequency of the noise signal is corrected based on the total input capacitance to obtain the corrected noise signal.

[0007] According to embodiments of this 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 in a non-inverting amplifier configuration to control the amplification factor of the device under test module.

[0008] According to embodiments of this disclosure, the device under test module further includes: a first switch for controlling the on / off state of the operational amplifier; a second switch for adjusting the amplification factor by controlling the on / off state of the first resistor; and a third switch for adjusting the amplification factor by controlling the on / off state of the second resistor.

[0009] According to an embodiment of this 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 are connected to form a non-inverting amplifier to amplify the noise signal output by the device under test module; and a fourth switch for adjusting the amplification factor by controlling the on / off state of the fourth resistor.

[0010] According to an embodiment of this disclosure, the capacitance testing module includes: a capacitor under test; a fifth resistor; a sixth resistor connected in parallel with the fifth resistor, wherein the sixth resistor, the fifth resistor, and the capacitor under test together form a resistor-capacitor circuit; and a fifth switch for controlling the on / off state of the resistor-capacitor circuit.

[0011] According to embodiments of this disclosure, the total input capacitance C of the device under test module is... TEST for:

[0012]

[0013] Where R6 represents the resistance value of the sixth resistor, and f1 represents the cutoff frequency of the system.

[0014] According to embodiments of this disclosure, the corrected noise signal i n for:

[0015]

[0016] Among them, V O_noiseThis represents the noise signal amplified by the device under test (DUT) module and the auxiliary amplifier module. G1 represents the amplification factor of the DUT module, G2 represents the amplification factor of the auxiliary amplifier module, and e n R represents the thermal noise voltage of the sampling resistor. S C represents the resistance value of the sampling resistor. TEST This indicates the capacitance value of the capacitor being tested.

[0017] According to embodiments of this disclosure, the apparatus further includes a power supply module for providing a stable voltage to the device under test module and the auxiliary amplifier module.

[0018] According to embodiments of this 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, thereby reducing the impact of voltage fluctuations on system performance.

[0019] Another aspect of this disclosure provides a method for testing operational amplifier current noise, the method comprising: converting current noise at the input 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 stray capacitance introduced by the system; after obtaining the total input capacitance, correcting the attenuation frequency of the noise signal based on the total input capacitance to obtain the corrected noise signal.

[0020] The operational amplifier current noise testing apparatus and method provided in this disclosure have at least the following beneficial effects:

[0021] (1) The operational amplifier current noise testing device and method provided in this embodiment of the present disclosure finds the location of the introduced pole (frequency attenuation) by testing the input terminal capacitor, and compensates for the influence of the pole introduced by the sampling resistor and stray capacitance by mathematical correction, thereby accurately measuring the current noise characteristics of the operational amplifier.

[0022] (2) The operational amplifier current noise testing device and method provided in this embodiment do not require expensive precision resistors and capacitors. They only need to set up an additional input capacitance testing circuit to accurately measure the total input capacitance of the operational amplifier. Based on the resistance value of the set sampling resistor and the size of the total input capacitance, the accurate position of the introduced pole is obtained. The influence of the pole is corrected from the noise curve obtained in the end, thereby obtaining accurate input current noise. Attached Figure Description

[0023] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0024] Figure 1A schematic diagram of a conventional operational amplifier current noise test circuit is shown.

[0025] Figure 2 A schematic diagram of a structural apparatus for testing operational amplifier current noise according to an embodiment of the present disclosure is shown.

[0026] Figure 3 A schematic diagram illustrating the structure of an operational amplifier current noise source according to an embodiment of the present disclosure is shown.

[0027] Figure 4 The diagram illustrates the operational amplifier current noise profile obtained directly.

[0028] Figure 5 The diagram illustrates the operational amplifier current noise profile after eliminating the effects of introduced poles.

[0029] Figure 6 A flowchart illustrating an operational amplifier current noise test method according to an embodiment of the present disclosure is shown schematically. Detailed Implementation

[0030] The embodiments of the present disclosure will now 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 disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0031] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

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

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

[0034] High-precision, low-noise operational amplifiers are widely used in the core components of signal receiving systems, finding broad applications in audio, communication, and instrumentation. In practical applications, when the source impedance of the operational amplifier is high, its current noise significantly impacts signal detection accuracy. With the rapid development of integrated circuit technology, internationally available operational amplifiers have achieved input current noise densities as low as 100 fA / √Hz at 1kHz. However, current noise levels of 100 fA / √Hz are easily affected by environmental interference and the precision of the test circuit, making accurate measurement difficult in actual testing. Therefore, researching testing methods for operational amplifier current noise is of increasing importance.

[0035] The conventional method for testing operational amplifier current noise is to place a sampling resistor at the input of the operational amplifier to convert the current noise into voltage noise for testing. The size of the sampling resistor should be selected such 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. In this case, the current noise becomes the main noise source. 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, the current noise that varies with frequency can be displayed.

[0036] However, in practical applications, when testing relatively small current noise, a large sampling resistor is required at the amplifier input to prevent the voltage noise converted from the current noise from being overwhelmed by the thermal noise of the sampling resistor itself. Furthermore, in current noise testing systems, the capacitance at the operational amplifier input is highly susceptible to stray capacitance. This results in a low peak in the noise testing system due to the combined effect of the large sampling resistor and stray capacitance, causing the measured noise to attenuate at lower frequencies, making it impossible to accurately measure the current noise of the operational amplifier. This is exemplified by conventional current noise testing methods in existing technologies.

[0037] Figure 1 The schematic diagram shows the structure of a conventional operational amplifier current noise test circuit.

[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 terminal of the operational amplifier and uses this sampling resistor to convert the current noise into voltage noise for testing.

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

[0040] (1)

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

[0042] Current noise will become the main noise source. By analyzing the relationship between resistive thermal noise and current noise, the current noise that varies with frequency can be displayed.

[0043] Conventional methods 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 influence 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 terminal to obtain the input current noise of the operational amplifier.

[0044] Analysis reveals the following shortcomings in current conventional operational amplifier current noise testing techniques:

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

[0046] (2) When the input stray capacitance is large, the sampling resistor and stray capacitance introduce a relatively low frequency pole, making it impossible to accurately obtain the high frequency current noise characteristics.

[0047] Based on this, the present disclosure provides an operational amplifier current noise testing device that does not require expensive precision resistors and capacitors. It only requires setting up an additional input capacitance testing circuit to accurately measure the total input capacitance of the operational amplifier. Based on the resistance value of the set sampling resistor and the size of the total input capacitance, the accurate location of the introduced pole (frequency attenuation) can be obtained. The influence of the pole can be corrected from the final noise curve to obtain the accurate input current noise.

[0048] The device includes: a device under test module, comprising an operational amplifier under test and a sampling resistor, wherein the sampling resistor is used to convert the current noise at the input 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, the total input capacitance including the input capacitance of the operational amplifier itself and stray capacitance introduced by the system; wherein, after obtaining the total input capacitance, the attenuation frequency of the noise signal is corrected based on the total input capacitance to obtain the corrected noise signal.

[0049] The operational amplifier current noise testing device provided in this embodiment of the invention finds the location of the introduced poles by testing the input capacitance and compensates for the influence of the poles introduced by the sampling resistor and stray capacitance through mathematical correction, thereby accurately measuring the current noise characteristics of the operational amplifier.

[0050] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0051] Figure 2 A schematic diagram of a structural apparatus for testing operational amplifier current noise according to an embodiment of the present disclosure is shown.

[0052] like Figure 2 As shown, the structure of the operational amplifier current noise testing device in this embodiment 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 to the DUT module and the auxiliary amplifier module. CC and V EE This ensures that the operational amplifier can maintain normal operation during testing, and the noise introduced by the power supply module is negligible.

[0054] In this embodiment, the power supply module may include, for example, a low-noise power supply and a low-noise linear regulator, wherein the low-noise power supply is used to provide an input voltage; and 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: the operational amplifier under test, sampling resistors (first resistor R1, second resistor R2), first switch S1, second switch S2, and 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 of the operational amplifier into voltage noise. The value of the sampling resistor is the parallel resistance of the first resistor R1 and the second resistor R2. The first resistor R1 and the second resistor R2 are connected in a non-inverting amplifier configuration to control the amplification factor of the device under test module.

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

[0058] In the actual design of the test circuit, appropriate sampling resistors and amplification factors can be designed according to the current noise levels of different operational amplifiers under test. The sampling resistors and amplification factors can be adjusted using the second switch S2 and the third switch S3. The output signal of the DUT module can be displayed at V... O_DUT The port is monitored to determine the working status of the DUT module.

[0059] The auxiliary amplifier module is used to further amplify voltage noise, so that even small noise signals can be accurately detected by a 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] Among them, the third resistor R3 and the fourth resistor R4 are connected in parallel, and the two are connected to form a non-inverting 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] In the actual design of the test circuit, the amplification factor of the auxiliary amplifier can be designed according to the magnitude of the DUT module output signal and the detection accuracy of the noise analyzer, and the amplification factor can be adjusted by the fourth switch S4. The output signal of the auxiliary amplifier module (the signal after the total noise at the input terminal is amplified by the DUT module and the auxiliary amplifier) ​​can be measured at V. O_noise The port is tested to determine the operating 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 (DUT) module. The total input capacitance includes the input capacitance of the operational amplifier itself, as well as stray capacitance introduced by the system.

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

[0065] Among them, the fifth resistor R5 and the sixth resistor R6 are connected in parallel, and the capacitor under test, the fifth resistor R5 and the sixth resistor R6 together form an RC circuit (resistor-capacitor circuit); the fifth switch R5 is used to control the opening and closing of this RC circuit.

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

[0067] After obtaining the total input capacitance through testing, the attenuation frequency of the noise signal is corrected based on the total input capacitance to obtain the corrected noise signal. Specifically, based on the set value of the sampling resistor and the size of the total input capacitance, the accurate location of the introduced pole is obtained, thus obtaining the final noise signal.

[0068] In this embodiment, the selection principle for the sampling resistor must follow the following constraints:

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

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

[0071] (2)

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

[0073] (3)

[0074] Let the voltage noise obtained from the conversion be greater than the thermal noise of the sampling resistor:

[0075] (4)

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

[0077] (5)

[0078] Further adjustments to the DUT module amplification factor, such as the sampling resistor at the positive input and the operational amplifier's input current, will limit the operational amplifier's offset voltage. For example, the operational amplifier's input current I... b =10pA, sampling resistor R S =10GΩ, then 10pA×10GΩ=100mV. After amplification by the DUT module, the voltage must not exceed the power supply voltage range to ensure that the operational amplifier is in normal working condition. This serves as a constraint for selecting the sampling resistor.

[0079] (6)

[0080] Where G1 represents the magnification factor of the DUT module; V CC This indicates the power supply voltage.

[0081] In the capacitance testing module, when testing the input capacitance and stray capacitance of the operational amplifier, the operational amplifier is connected as a follower, and the capacitor under test, C... TEST The resistor and the circuit will form an RC loop. Since the value of the resistor is known, the total input capacitance can be accurately determined by testing the -3dB frequency of the circuit.

[0082] Figure 3 A schematic diagram of a current noise source for an operational amplifier according to an embodiment of the present disclosure is shown.

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

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

[0085] (7)

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

[0087] With a current noise of 100 fA / √Hz at 1 kHz, 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 see that the sampling resistor should be greater than 14.81MΩ, so a 20MΩ sampling resistor can be selected. Set the DUT module amplification factor G1 = 11 times, then the bias current I... b The maximum output voltage V of the DUT module caused out_ib for:

[0089] (8)

[0090] This allows the amplifier to operate normally.

[0091] Close the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4, and open the remaining switches to make the circuit work in the current noise test mode. The DUT module amplifies by G1 times, and the auxiliary operational amplifier amplifies by 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 follows:

[0093] (9)

[0094] And can obtain such as Figure 4 The input current noise curve is shown.

[0095] Figure 4 The schematic diagram shows the operational amplifier current noise curve obtained directly.

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

[0097] To eliminate the effects of poles introduced by the sampling resistor and input stray capacitance, close the third switch S3 and the fifth switch S5 to set the circuit to total input capacitance test mode and test the input capacitance of the operational amplifier. The fifth resistor R5 can be set to 50Ω and the sixth resistor R6 to 1MΩ, configuring the operational amplifier as a follower. Test using a network analyzer and a power divider, at V... I_SIG The input signal is at V. O_SIG If the terminal detection signal is read at a frequency point f1 of -3dB from the network analyzer test results, then the total input capacitance of the operational amplifier is:

[0098] (10)

[0099] Where R6 represents the resistance value of the sixth resistor, and f1 represents the cutoff frequency of the system.

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

[0101] (11)

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

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

[0104] Figure 5 The schematic diagram shows the current noise curve of the operational amplifier after eliminating the effects of introduced poles.

[0105] like Figure 5 As shown, the operational amplifier current noise testing device provided in this embodiment effectively solves the non-ideal factors caused by large sampling resistors and input stray capacitances.

[0106] The operational amplifier current noise testing device provided in this embodiment does not require expensive precision resistors and capacitors. It only requires setting up an additional input capacitance testing circuit to accurately measure the total input capacitance of the operational amplifier. Based on the resistance value of the set sampling resistor and the size of the total input capacitance, the accurate location of the introduced pole is obtained. The influence of the pole is corrected from the final noise curve, thereby obtaining accurate input current noise.

[0107] Another aspect of this disclosure provides a method for testing operational amplifier current noise, such as... Figure 6 As shown.

[0108] Figure 6 A flowchart illustrating an operational amplifier current noise test method according to an embodiment of the present disclosure is shown schematically.

[0109] like Figure 6 As shown, the operational amplifier current noise testing method according to an embodiment of this 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 utilizes an auxiliary amplifier module to further amplify the voltage noise.

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

[0113] S4. After obtaining the total input capacitance through testing, the attenuation frequency of the noise signal is corrected based on the total input capacitance to obtain the corrected noise signal.

[0114] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions. Those skilled in the art will understand that the features described in the various embodiments of the present disclosure can be combined and / or combined in various ways, even if such combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments of this disclosure may be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0115] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. An operational amplifier current noise test apparatus, characterized by, 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 an 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 total input capacitance of the device-under-test module, wherein the total input capacitance comprises input capacitance of the operational amplifier itself and stray capacitance introduced by a system; wherein after the total input capacitance is obtained through testing, an attenuation frequency of a noise signal is corrected according to the total input capacitance, to obtain a corrected noise signal.

2. The apparatus of claim 1, wherein, The sampling resistor comprises: a first resistor; a second resistor connected in parallel with the first resistor, wherein the first resistor and the second resistor control an amplification factor of the device-under-test module by being connected as a non-inverting amplifier.

3. The apparatus of claim 2, wherein, The device-under-test module further comprises: a first switch used to control on-off of the operational amplifier; a second switch used to adjust the amplification factor by controlling on-off of the first resistor; a third switch used to adjust the amplification factor by controlling on-off of the second resistor.

4. The apparatus of claim 1, wherein, The auxiliary amplifier module comprises: 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 as a non-inverting amplifier; a fourth switch used to adjust the amplification factor by controlling on-off of the fourth resistor.

5. The apparatus of claim 1, wherein, The capacitance test module comprises: a 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 tested together form a resistor-capacitor loop; a fifth switch used to control on-off of the resistor-capacitor loop.

6. The apparatus of claim 5, wherein, The total input capacitance C of the device module under test TEST is: Wherein, R6 represents a resistance value of the sixth resistor, and f1 represents a cut-off frequency of the system.

7. The apparatus of claim 6, wherein, The modified noise signal i n is: wherein V O_noise represents the noise signal 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, e n represents the thermal noise voltage of the sampling resistor, R S represents the resistance value of the sampling resistor, C TEST represents the capacitance value of the capacitor to be measured.

8. The apparatus of claim 1, wherein, The device further comprises: a power supply module used to provide stable voltage for the device-under-test module and the auxiliary amplifier module.

9. The apparatus of claim 8, wherein, The power supply module comprises: a low-noise power supply used to provide input voltage; a low-noise linear voltage stabilizer used to adjust the input voltage provided by the low-noise power supply into stable output voltage, to reduce the influence of voltage fluctuation on system performance.

10. A method of testing current noise of an operational amplifier, the method comprising: The method comprises: converting current noise at an input end of an operational amplifier into voltage noise; further amplifying the voltage noise; testing total input capacitance, wherein the total input capacitance comprises input capacitance of the operational amplifier itself and stray capacitance introduced by a system; after the total input capacitance is obtained through testing, correcting an attenuation frequency of a noise signal according to the total input capacitance, to obtain a corrected noise signal.

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