CN217332667U - Power supply rejection ratio test system - Google Patents
Power supply rejection ratio test system Download PDFInfo
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- CN217332667U CN217332667U CN202220484403.8U CN202220484403U CN217332667U CN 217332667 U CN217332667 U CN 217332667U CN 202220484403 U CN202220484403 U CN 202220484403U CN 217332667 U CN217332667 U CN 217332667U
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Abstract
A power supply rejection ratio test system, comprising: the signal processing module is used for outputting alternating current modulation signals of preset frequency points; the test module is connected with the signal processing module and used for acquiring the alternating current modulation signal, superposing the alternating current modulation signal with a preset direct current signal and then outputting a test voltage signal to a product to be tested, wherein the preset frequency point is within the frequency bandwidth range of the test module; the current source module is connected between the input end and the output end of the product to be tested and used for providing load current; and the signal processing module is connected with the sampling end of the product to be tested, and is also used for acquiring a test voltage signal and an output signal of the product to be tested when the test voltage signal is input through the sampling end and calculating a power supply rejection ratio of a preset frequency point. The load current is provided by the current source module, a circulating current with a specific size can be generated between the input end and the output end of the product to be measured, the capacitance value of the input end capacitor of the product to be measured can be reduced, and the accuracy of the PSRR measurement result is improved.
Description
Technical Field
The application relates to the technical field of electronics, in particular to a power supply rejection ratio testing system.
Background
PSRR (power supply rejection ratio) is the ratio of the input power supply variation to the converter output variation, and is usually expressed in decibels. The formula of PSRR is: PSRR ═ 20. log. (Δ Vout/Δ Vin), where Δ Vout represents the output variation and Δ Vin represents the input variation, and the larger the absolute value of PSRR, the stronger the suppression capability of the output on the input disturbance signal, and the better the performance. The rationale for PSRR measurement: the input end voltage is modulated by an alternating current modulation signal with variable frequency, then the output voltage is measured at the output end, and the fluctuation amplitude of the output voltage is compared with the fluctuation amplitude of the input end voltage, so that the power supply rejection ratio can be obtained.
When testing the power supply rejection ratio of a high-power LDO (linear regulator), an input capacitor needs to be connected to the input end of the LDO to be tested to ensure the normal start of the LDO to be tested.
SUMMERY OF THE UTILITY MODEL
In view of this, the present application provides a power supply rejection ratio test system, so as to solve the problem that when the power supply rejection ratio of a high-power LDO is tested by an existing power supply rejection ratio test system, an input capacitor needs to be connected to an input end of the LDO to be tested, and as the frequency of an ac modulation signal at the input end continuously increases, an input signal of the LDO to be tested is gradually attenuated, resulting in a low PSRR measurement result accuracy.
The application provides a power supply rejection ratio test system, includes: the signal processing module is used for outputting an alternating current modulation signal of a preset frequency point; the test module is connected with the signal processing module and used for acquiring the alternating current modulation signal, superposing the alternating current modulation signal with a preset direct current signal and outputting a test voltage signal to a product to be tested, wherein the preset frequency point is within the frequency bandwidth range of the test module; the current source module is connected between the input end and the output end of the product to be tested and used for providing load current; the signal processing module is connected with a sampling end of a product to be tested, and is further used for acquiring the test voltage signal and an output signal of the product to be tested when the test voltage signal is input through the sampling end, and extracting alternating current signals in the test voltage signal and the output signal to calculate the power supply rejection ratio of the preset frequency point.
Optionally, the current source module includes at least one of a digital source table and a current source.
Optionally, the signal processing module includes at least one of a network analyzer, a signal generator, and a microprocessor.
Optionally, the test module includes an operational amplifier unit and a dc power supply; the first input end of the operational amplification unit is connected with the output end of the signal processing module and is used for acquiring the alternating current modulation signal; the second input end of the operational amplification unit is connected with the output end of the direct current power supply and is used for acquiring the preset direct current signal; the operational amplification unit is used for outputting the test voltage signal according to the alternating current modulation signal and the preset direct current signal; the preset frequency point is in the frequency bandwidth range of the operational amplification unit.
Optionally, the operational amplification unit includes at least one operational amplifier; the voltage end of the operational amplifier is connected with a power supply voltage, a positive input end is used as the first input end, and a negative input end is used as the second input end; the bandwidth of the operational amplifier covers the bandwidth of the alternating current modulation signal; the output impedance of the operational amplifier is less than a preset impedance threshold.
Optionally, the preset impedance threshold is less than 5 ohms.
Optionally, the system further comprises a bias voltage module; the bias voltage module is connected with a bias voltage end of a product to be tested and used for providing bias voltage.
Optionally, the bias voltage module comprises a programmable voltage source.
Optionally, when the current source module is a digital source table, the digital source table is a 4-phase limited source table.
Optionally, when the signal processing module is a network analyzer, a first output end of the network analyzer is connected to the positive input end of the operational amplifier, and a second output end of the network analyzer is grounded to output the differential ac modulation signal; the first output end of the operational amplifier is connected with the input end of a product to be tested, and the second output end of the operational amplifier is grounded so as to output the test voltage signal in a differential form; the first input end, the second input end, the third input end and the fourth input end of the network analyzer are respectively connected with the sampling input end, the sampling output end, the first sampling sample area and the second sampling ground of a product to be tested and used for acquiring the test voltage signal in a differential form and the output signal in the differential form of the product to be tested.
The utility model provides a pair of power supply rejection ratio test system, through current source module, connect between the input and the output of the product that awaits measuring, a load current is used for providing, this load current gets back to current source module again behind the input to the output of the product that awaits measuring via the input of the product that awaits measuring, can produce the circulating current of a specific size between the input of the product that awaits measuring and the output, this electric current can replace the load current of the product during operation that awaits measuring, because this current source module can provide a circulating current for the input of the product that awaits measuring, can reduce the electric current that awaits measuring the product input end circuit provided greatly, consequently, can reduce the appearance value of the product input electric capacity that awaits measuring, and then reduced the attenuation degree to the input AC modulation signal, the accuracy of PSRR measuring result has been improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a power supply rejection ratio test system according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a power supply rejection ratio test system according to an embodiment of the present application;
fig. 3 is a schematic structural diagram of a power supply rejection ratio test system according to an embodiment of the present application.
Detailed Description
As described in the background art, when testing the power supply rejection ratio of a high-power LDO (linear regulator), an input capacitor needs to be connected to an input terminal of the LDO to be tested, and as the frequency of an ac modulation signal at the input terminal continuously increases, an input signal of the LDO to be tested is gradually attenuated, which results in a low PSRR measurement result accuracy.
The inventor finds that PSRR measurement of LDOs can be achieved using two ways. The first method is as follows: the PSRR measurement of the LDO under test can be achieved using a vector analyzer and a linear injector. Specifically, the linear injector is connected between the output end of the vector analyzer and the input end of the LDO to be tested. The vector analyzer can output an alternating current modulation signal with variable frequency to modulate the voltage of the input end of the LDO to be detected, and simultaneously measure the alternating current disturbance of the input end and the alternating current disturbance of the output end of the LDO to be detected, so that the power supply rejection ratio of the LDO to be detected is obtained. The disadvantages of this solution are 2, first: because the linear injector is connected in series at the input end of the LDO to be tested, an input current passes through the linear injector, so that the linear injector generates a large voltage drop, and the voltage drop changes greatly along with the heat generation of the linear injector, thereby affecting the accuracy of the PSRR measurement result of the LDO to be tested. Secondly, the method comprises the following steps: because the output of the linear injector is of a certain resistance, the impedance and an input capacitor (usually 10uF) connected with the input end of the LDO to be measured form a low-pass filter, along with the continuous increase of the frequency of the input end alternating current modulation signal, the low-pass filter can cause the input end signal of the LDO to be measured to be gradually attenuated, for example, when the frequency of the input end alternating current modulation signal reaches 1MHz, the input end signal of the LDO to be measured can be attenuated to a microvolt level, at the moment, the input end signal of the LDO to be measured is too small, the input end signal is not easy to be identified by a vector analyzer, and simultaneously, the input end signal is lower than the bottom noise of a test system, so that the accuracy of a PSRR measurement result is lower.
The second method comprises the following steps: the PSRR measurement of the LDO to be measured can be realized by using a vector analyzer and a blocking capacitor. Specifically, the blocking capacitor is connected between the output end of the vector analyzer and the input end of the LDO to be tested. The function of the vector analyzer is the same as described above and will not be described herein. The main function of the dc blocking capacitor is to prevent the dc component from passing through. The disadvantages of this solution are 2, first: because the vector analyzer has an output impedance of 50 Ω (ohm), the LDO under test cannot be directly loaded for PSRR testing. Secondly, the method comprises the following steps: the 50 omega output impedance of the vector analyzer and the input end capacitor form a low-pass filter, and along with the continuous increase of the frequency of the input end alternating current modulation signal, the low-pass filter can cause the input end signal of the LDO to be measured to be gradually attenuated, so that the accuracy of the PSRR measurement result is low.
In addition, as the power of the LDO to be tested increases, the capacitance of the input end of the LDO to be tested during PSRR measurement also increases correspondingly, so that the signal of the input end is further attenuated, and the accuracy of the test result is further reduced.
In order to solve the above problems, the present application provides a power supply rejection ratio test system, which is connected between an input end and an output end of a product to be tested through a current source module, and is configured to provide a load current, where the load current returns to the current source module after passing through the input end to the output end of the product to be tested, so that a circulating current of a specific magnitude can be generated between the input end and the output end of the product to be tested, and the current can replace the load current of the product to be tested during operation.
The technical solutions in the embodiments of the present application are clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. The following embodiments and their technical features may be combined with each other without conflict.
Please refer to fig. 1, a schematic structural diagram of a power supply rejection ratio testing system according to an embodiment of the present application.
The power supply rejection ratio test system 1 of the present embodiment includes: a signal processing module 11, a test module 12 and a current source module 13.
And the signal processing module 11 is configured to output an ac modulation signal with a preset frequency point.
From the above discussion, the basic principle of PSRR measurement is: the input end voltage is modulated by an alternating current modulation signal with variable frequency, then the output voltage is measured at the output end, and the fluctuation amplitude of the output voltage is compared with the fluctuation amplitude of the input end voltage, so that the power supply rejection ratio can be obtained. The signal processing module 11 is used to output an ac modulation signal with variable frequency, specifically, the frequency range of the ac modulation signal is 10Hz to 10MHz, that is, the range of the preset frequency point is 10Hz to 10 MHz.
In this embodiment, the signal processing module 11 includes a network analyzer, and in other alternative embodiments, the signal processing module 11 may further include at least one of a signal generator and a microprocessor.
And the test module 12 is connected with the signal processing module 1 and used for acquiring the alternating current modulation signal, superposing the alternating current modulation signal with a preset direct current signal and then outputting a test voltage signal to a product to be tested, wherein the preset frequency point is in the frequency bandwidth range of the test module 12. The test module 12 superposes the alternating current modulation signal with a preset direct current signal to realize signal modulation, and the modulated signal is a test voltage signal; meanwhile, the bandwidth of the test module 12 is controlled to enable the preset frequency point to be within the bandwidth range of the test module 12, so that the test module 12 can be prevented from causing signal attenuation of the test voltage signal, and the accuracy of the PSRR test result is improved. The product to be tested comprises a high-power LDO, and when the power supply rejection ratio of the high-power LDO is measured, the frequency of a test voltage signal can reach more than 1 MHz. In other alternative embodiments, the product to be tested may also be other electronic products.
And the current source module 13 is connected between the input end IN and the output end OUT of the product to be tested and used for providing load current. This load current gets back to current source module 13 after the input IN of the product that awaits measuring gets back to output OUT again, can produce the circulating current of a specific size between the input IN of the product that awaits measuring and output OUT, this current can replace the load current of the product during operation that awaits measuring, because this current source module 13 can provide a circulating current for the input IN of the product that awaits measuring, the electric current that the product input end circuit that can significantly reduce to await measuring provided, consequently, can reduce the appearance value of the product input capacitance that awaits measuring, and then reduced the attenuation degree to the input alternating current modulation signal, PSRR measuring result accuracy has been improved. The current source module 13 includes at least one of a digital source table and a current source. In this embodiment, when the current source module 13 is a digital source table, the digital source table is a 4-phase limited source table. In other alternative embodiments, the current source module 13 may be a current source, which is a programmable current source to output currents of different magnitudes.
The signal processing module 11 is connected to a sampling end of a product to be tested, and is further configured to obtain the test voltage signal and an output signal of the product to be tested when the test voltage signal is input through the sampling end, and extract the test voltage signal and an alternating current signal in the output signal to calculate a power supply rejection ratio of the preset frequency point.
The network analyzer in this embodiment is a vector network analyzer, and the vector network analyzer functions as follows: the method comprises the steps of outputting an alternating current modulation signal required by measurement, simultaneously connecting the alternating current modulation signal with a sampling end of a product to be measured, acquiring a test voltage signal of an input end of the product to be measured and an output signal of the product to be measured when the test voltage signal is input, extracting the alternating current signal from the test voltage signal and the output signal of the input end, and calculating a power supply rejection ratio of a preset frequency point according to the formula.
The power supply rejection ratio parameter comprises a test voltage signal of an input end of a product to be tested and an output signal of the product to be tested when the test voltage signal is input, and the power supply rejection ratio parameter changes along with frequency, so the vector network analyzer needs to scan power supply rejection ratio data corresponding to each frequency point according to a specified frequency interval, and finally a curve graph of PSRR data changing along with frequency is drawn.
The power supply rejection ratio test system of this embodiment, connect between the input and the output of the product that awaits measuring through current source module, a load current is used for providing, this load current gets back to current source module again behind the input to the output of the product that awaits measuring via the input of the product that awaits measuring, can produce the circulating current of a specific size between the input of the product that awaits measuring and the output, this electric current can replace the load current of the product during operation that awaits measuring, because this current source module can provide a circulating current for the input of the product that awaits measuring, can reduce the electric current that awaits measuring the product input end circuit provided greatly, consequently, the capacity value of the product input end electric capacity that awaits measuring can be reduced, and then the attenuation degree to the input AC modulation signal has been reduced, the accuracy of PSRR measuring result has been improved.
In an alternative embodiment, the test module 12 includes an operational amplifier unit and a dc power supply; a first input end of the operational amplification unit is connected with an output end of the signal processing module 11, and is used for acquiring the alternating current modulation signal; the second input end of the operational amplification unit is connected with the output end of the direct-current power supply and is used for acquiring the preset direct-current signal; the operational amplification unit is used for outputting the test voltage signal according to the alternating current modulation signal and the preset direct current signal; the preset frequency point is in the frequency bandwidth range of the operational amplification unit.
The operational amplification unit comprises any device capable of realizing an amplification function, and the operational amplification unit with a wider frequency bandwidth is selected, so that a preset frequency point is within the frequency bandwidth range of the operational amplification unit, the operational amplification unit can be prevented from causing signal attenuation of a test voltage signal, and the accuracy of a PSRR test result is improved.
In an alternative embodiment, the operational amplifier unit includes at least one operational amplifier; the voltage end of the operational amplifier is connected with a power supply voltage, a positive input end is used as the first input end, and a negative input end is used as the second input end; the bandwidth of the operational amplifier covers the bandwidth of the alternating current modulation signal; the output impedance of the operational amplifier is less than a preset impedance threshold. In this embodiment, the operational amplification unit includes one operational amplifier, and in alternative embodiments, the operational amplification unit may include another number of operational amplifiers.
Because the network analyzer has 50 omega output impedance, the input impedance of the operational amplifier is infinite under the ideal condition, the network analyzer can work normally when the alternating current signal output by the network analyzer has 50 omega impedance, and the stability of a test system is ensured; the output impedance of the operational amplifier is smaller than a preset impedance threshold, for example, the preset impedance threshold is smaller than 5 ohms, in this embodiment, the output impedance of the operational amplifier is 0.04 Ω, and a strong loading capability can be provided.
Please refer to fig. 2, a schematic structural diagram of a power supply rejection ratio testing system according to an embodiment of the present application.
The power supply rejection ratio test system of the embodiment further includes a bias voltage module 14 on the basis of the above embodiment; the bias voltage module 14 is connected to a bias voltage terminal of the product to be tested, and is configured to provide a bias voltage. The bias voltage module 14 is used for adjusting an input voltage range of a product to be tested, improving the input voltage range of the product to be tested while improving the accuracy of a test result of the PSRR, and improving an application scenario of a power supply rejection ratio test system. In this embodiment, the bias voltage module 14 includes a programmable voltage source, and in other alternative embodiments, the bias voltage module 14 may select another circuit capable of providing the bias voltage according to actual needs, for example, a voltage dividing circuit formed by an adjustable resistor.
Referring to fig. 3, a schematic structural diagram of a power supply rejection ratio testing system according to an embodiment of the present application is shown.
In the power supply rejection ratio testing system of this embodiment, the signal processing module 11 is a vector network analyzer, such as Bode100, the testing module 12 includes an operational amplifier, such as the operational amplifier THS3120, the current source module 13 includes a 4-phase limit source table, such as a key voltage table 2602B source table of gieviley, and the bias voltage module 14 includes a programmable voltage source. The product to be detected is a high-power linear power supply product, such as a linear power supply Au 8010.
A first output end of the network analyzer is connected with a positive input end of the operational amplifier, and a second output end of the network analyzer is grounded so as to output the differential alternating current modulation signal; the first output end of the operational amplifier is connected with the input end of a product to be tested, and the second output end of the operational amplifier is grounded so as to output the test voltage signal in a differential form; the first input end, the second input end, the third input end and the fourth input end of the network analyzer are respectively connected with a sampling input end IN _ sns, a sampling output end OUT _ sns, a first sampling sample GND _ sns1 and a second sampling sample GND _ sns2 of a product to be tested, and are used for acquiring the test voltage signal IN a differential form and an output signal IN a differential form of the product to be tested. Two ends of the programmable voltage source are respectively connected with a BIAS voltage end BIAS and a ground GND of a product to be tested.
The vector network analyzer has the functions of: injecting an alternating current modulation signal in a range of 10Hz-10MHz required by measurement, and simultaneously measuring an input end signal and an output end signal of a product to be measured so as to obtain a power supply rejection ratio parameter, wherein the power supply rejection ratio parameter is changed along with frequency, so that the vector network analyzer needs to scan power supply rejection ratio data corresponding to each frequency point according to a specified frequency interval, and finally drawing a curve graph of PSRR data changing along with frequency.
The operational amplifier needs to be powered by positive and negative voltages, where a power supply is used to generate +/-12V supply voltage to the operational amplifier, the power supply having three ports, one of which outputs positive 12V voltage, the second of which is grounded, and the third of which outputs negative 12V voltage. The operational amplifier also comprises two differential input ends which are respectively a negative input end and a positive input end, wherein the negative input end is connected with the output end of a direct current power supply, the direct current power supply is used for providing direct current voltage, and the direct current voltage is used as a preset direct current signal; the positive input of the operational amplifier is connected with the output end of the vector network analyzer, and the vector network analyzer is used for providing an alternating current modulation signal which comprises an alternating current voltage. This produces a voltage signal at the output of the operational amplifier that is a superposition of the dc signal and the ac signal, for example a 1.4V dc voltage superimposed with a 25mV ac voltage signal.
The power supply rejection ratio test system of the embodiment adopts the high-bandwidth operational amplifier, ensures that the frequency of the alternating current modulation signal is within the bandwidth range of the operational amplifier, and can prevent the signal attenuation of the alternating current modulation signal caused by the bandwidth of the operational amplifier from influencing the accuracy of the PSRR test result. Specifically, in this embodiment, the frequency range of the ac modulation signal is 10Mz-10MHz, and the voltage amplitude is 20 mV. The bandwidth of the high-bandwidth operational amplifier is 0-120MHz and is enough to cover the highest frequency 10MHz of an alternating current modulation signal required by a test, so that the high-bandwidth operational amplifier is used for supplying power to the input end of a product to be tested, and the input alternating current modulation signal cannot be attenuated.
One end of the input capacitor C1 is connected with the input end of the product to be tested, and the other end is grounded. The capacitance value of the input capacitance C1 is at least 1 uF.
The 4-phase limited source meter in the embodiment uses the function of the current source to provide load current for the product to be tested. The load current flows into the input end of the product to be detected, and forms a circulating current through the output end of the product to be detected, so that the output current value of the operational amplifier is reduced.
The specific principle of the power supply rejection ratio test system of the embodiment for performing the PSRR test is as follows:
the input end IN of the product to be tested is connected with the output end of the operational amplifier, the output end of the operational amplifier provides direct current input voltage and modulated alternating current signal voltage required by the product to be tested to work, the 4-phase line source meter is bridged at the input end and the output end of the product to be tested, the source meter generates set current at the input end of the product to be tested, the set current finally returns to the negative end of the source meter from the input end to the output end of the product to be tested, circulating current with specific size is generated between the input end IN and the output end OUT of the product to be tested, and the current can replace load current of the product to be tested when the product to be tested works. At the moment, alternating current signals of the input end and the output end of the product to be tested are monitored by using a vector network analyzer, so that data of the power supply rejection ratio are obtained.
In the power supply rejection ratio test system of the embodiment, a 4-phase limit source meter (here, 2602B source meter) is used as a current load, and compared with a load (for example, an electronic load, a cement load is unlimited) connected between a positive output end and a negative output end (namely, ground) of a product to be tested in the prior art, the load of a direct current power supply at the input end of the product to be tested is greatly reduced. For example, when the load current is 3A (amperes), the load current is not necessarily supplied by the dc power source, but is supplied by a 4-phase limit source meter. This brings about 2 benefits: the 1 st advantage is that the power supply work of the operational amplifier to the product to be tested is well laid, because the operational amplifier can not provide more than 1A of direct current, the direct current load current of the part is born by a 4-phase limit source meter; the 2 nd benefit is that the input capacitance C1 that needs to be used when the product that awaits measuring takes 3A load current normal work can be dwindled, and input end capacitance needs 10uF at least among the prior art, and input capacitance C1 of input in this application only needs 1uF just enough, because input end capacitance reduces to later 1uF from original 10uF, and the capacitive reactance on the specific frequency point has also promoted 10 times, so to the decay greatly reduced to alternating signal, has improved the accuracy of PSRR test result.
The operational amplifier is characterized by high input impedance and low output impedance when the output impedance of the operational amplifier is less than a preset impedance threshold. The advantage of high input impedance is that the operational amplifier can be driven to work normally even if the injected AC modulation signal of the vector network analyzer has 50 omega impedance. Meanwhile, the other end of the input of the operational amplifier is connected with a direct current power supply, so that the output end signal of the operational amplifier, namely the test voltage signal, is a mixed signal obtained by superposing a preset direct current signal and an alternating current modulation signal at the input end, and the requirements of the work and the measurement of a rear-end product to be tested are just met. The benefit of a low output impedance of the operational amplifier is that it provides a strong load capability (referred to herein primarily as ac load capability, since dc load is provided by the 4-phase limited source table above). The output end of the operational amplifier can provide the loading capacity of at least 400mA, the output impedance is low, for example, the preset impedance threshold is 0.04 omega, and when the output impedance of the operational amplifier is as low as 0.04 omega, the signal output by the operational amplifier is enough to drive the capacitive load of 1uF in the range of 10Hz to 10 MHz. Compared with the prior art, the impedance of the vector network analyzer is high, so that the output alternating current signal is attenuated to be below 1mv and cannot be identified by the vector network analyzer, or is submerged by the bottom noise of the system, the power supply rejection ratio test system amplifies the alternating current modulation signal output by the vector network analyzer through the operational amplifier, and simultaneously provides low output impedance, so that the output test voltage signal can be ensured to be always kept at about 20mv in the whole measurement frequency interval, the high fidelity of the test result can be ensured, and the accuracy of the PSRR test result is improved. And meanwhile, the problem of large and unstable input voltage drop is not existed in the scheme using the linear injector, so that the manual test and the automatic test can be supported.
In summary, in the power supply rejection ratio test system of this embodiment, a 4-phase limit source table is used to bridge the input end and the output end of the product to be tested, where the 4-phase limit source table utilizes the function of its current source to replace the load current, and the 4-phase limit source table includes, but is not limited to, the 2602B described above; meanwhile, a high-bandwidth operational amplifier is used for superposing a preset direct current signal and an alternating current modulation signal to form a test voltage signal to the input end of a product to be tested, the high-bandwidth operational amplifier comprises but is not limited to the THS3120, the frequency of the alternating current modulation signal is within the bandwidth range of the operational amplifier, and the alternating current modulation signal can provide enough strong alternating current carrying capacity and low output impedance within the frequency range of 10MHz so as to ensure that the alternating current signal is not greatly attenuated by the capacitor at the input end; meanwhile, the combination of the operational amplifier and the 4-phase limit source table supplements each other, the operational amplifier does not need to provide overlarge direct current load, and the accuracy of the PSRR test result is improved.
The above-mentioned embodiments are only examples of the present application, and not intended to limit the scope of the present application, and all equivalent structures or equivalent flow transformations made by the contents of the specification and the drawings, such as the combination of technical features between the embodiments and the direct or indirect application to other related technical fields, are also included in the scope of the present application.
Claims (10)
1. A power supply rejection ratio test system, comprising:
the signal processing module is used for outputting an alternating current modulation signal of a preset frequency point;
the test module is connected with the signal processing module and used for acquiring the alternating current modulation signal, superposing the alternating current modulation signal with a preset direct current signal and outputting a test voltage signal to a product to be tested, wherein the preset frequency point is within the frequency bandwidth range of the test module;
the current source module is connected between the input end and the output end of the product to be tested and used for providing load current;
the signal processing module is connected with a sampling end of a product to be tested, and is further used for acquiring the test voltage signal and an output signal of the product to be tested when the test voltage signal is input through the sampling end, and extracting alternating current signals in the test voltage signal and the output signal to calculate the power supply rejection ratio of the preset frequency point.
2. The power supply rejection ratio test system of claim 1, wherein the current source module comprises at least one of a digital source table and a current source.
3. The power supply rejection ratio test system of claim 2, wherein said signal processing module comprises at least one of a network analyzer, a signal generator, and a microprocessor.
4. The power supply rejection ratio test system of claim 3, wherein said test module comprises an operational amplifier unit and a DC power supply;
the first input end of the operational amplification unit is connected with the output end of the signal processing module and is used for acquiring the alternating current modulation signal; the second input end of the operational amplification unit is connected with the output end of the direct current power supply and is used for acquiring the preset direct current signal; the operational amplification unit is used for outputting the test voltage signal according to the alternating current modulation signal and the preset direct current signal; the preset frequency point is in the frequency bandwidth range of the operational amplification unit.
5. The power supply rejection ratio test system of claim 4, wherein said operational amplification unit comprises at least one operational amplifier;
the voltage end of the operational amplifier is connected with a power supply voltage, a positive input end is used as the first input end, and a negative input end is used as the second input end;
the bandwidth of the operational amplifier covers the bandwidth of the alternating current modulation signal;
the output impedance of the operational amplifier is less than a preset impedance threshold.
6. The power supply rejection ratio test system of claim 5, wherein said predetermined impedance threshold is less than 5 ohms.
7. The power supply rejection ratio test system of claim 5, further comprising a bias voltage module;
the bias voltage module is connected with a bias voltage end of a product to be tested and used for providing bias voltage.
8. The power supply rejection ratio test system of claim 7, wherein said bias voltage module comprises a programmable voltage supply.
9. The power supply rejection ratio test system of claim 2, wherein when said current source module is a digital source table, said digital source table is a 4-phase limited source table.
10. The power supply rejection ratio test system of claim 5, wherein when said signal processing module is a network analyzer, a first output terminal of said network analyzer is connected to a positive input terminal of said operational amplifier, and a second output terminal thereof is grounded to output said ac modulation signal in differential form;
the first output end of the operational amplifier is connected with the input end of a product to be tested, and the second output end of the operational amplifier is grounded so as to output the test voltage signal in a differential form;
the first input end, the second input end, the third input end and the fourth input end of the network analyzer are respectively connected with the sampling input end, the sampling output end, the first sampling sample area and the second sampling ground of a product to be tested and used for acquiring the test voltage signal in a differential form and the output signal in the differential form of the product to be tested.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
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