CN107449949B - Device for applying DC bias voltage to AC sine wave signal source - Google Patents
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- CN107449949B CN107449949B CN201710795779.4A CN201710795779A CN107449949B CN 107449949 B CN107449949 B CN 107449949B CN 201710795779 A CN201710795779 A CN 201710795779A CN 107449949 B CN107449949 B CN 107449949B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention relates to a device for applying direct-current bias voltage to an alternating-current sine wave signal source, which comprises a signal source, a capacitor, a source resistor, a feedback resistor, a balance resistor, a measured piece, an integrated operational amplifier and an inverter, wherein the capacitor is connected with the signal source; the first integrated operational amplifier, the first resistor, the third resistor, the feedback resistor and the balance resistor form deep negative feedback to form a proportional amplifier; the second integrated operational amplifier, the second source resistor, the second resistor and the second capacitor form deep negative feedback to form an integrator. The invention forms a depth negative feedback circuit based on an integrated operational amplifier, and utilizes the principle that the infinite integral result of an integrator on an alternating current sine wave signal is zero, and a common high-precision integrated operational amplifier can accurately superimpose a direct current bias voltage on a sine wave signal source so as to form an alternating current-direct current signal source. The circuit has the advantages of simple and reliable structure, low overall complexity of the circuit, easy popularization and good application prospect.
Description
Technical Field
The invention relates to the field of electronic measurement and instruments, in particular to the technical field of AC/DC signal sources, and particularly relates to a device for applying DC bias voltage to an AC sine wave signal source.
Background
Impedance is one of the important physical parameters in electricity, and with the development of modern analog and digital technologies, an LCR digital bridge is the mainstream of impedance measurement, and tests the impedance value of a measured piece by applying an alternating sine wave signal with a certain frequency. In some specific occasions, the direct-current bias voltage needs to be applied to the measured piece, and then the impedance value measured by the alternating-current sine wave signal is applied, so that the characteristics of the measured piece in real application can be reflected more accurately.
The current sine wave signal superposition method of DC bias voltage is divided into two methods, one is a direct method, as shown in figure 1; the other is an indirect method as shown in fig. 2. The direct method is mainly used for testing capacitors or occasions with low requirements on testing precision, and has the main advantages of simple circuit structure, few electronic components and lower cost, and the defects of direct bias voltage Yi Rong under the influence of direct current resistance of a tested piece, especially under the condition of measuring resistance and inductance. The indirect method is based on the inverse summation operation of the integrated operational amplifier, and the direct-current bias voltage is accurately loaded on the tested piece, so that the method is widely applied to occasions with high test precision requirements. In the indirect method, the operational amplifier U1, the feedback resistor Rf1, the input resistor R1 and the balance resistor Rp form deep negative feedback by taking the operational amplifier U1 as a core, and the virtual short is established, so that the voltage applied to the tested piece is as follows
In reality, the integrated operational amplifier has nonideal index parameters such as temperature drift, offset voltage, offset current and the like, and the nonideal index parameters can lead to zero drift so as to influence the accuracy of direct current bias voltage. Although other components are reasonably selected by adopting the integrated operational amplifier with low offset, low temperature drift and high precision, the stability of the power supply voltage is improved, the environmental temperature change is reduced, the interference and noise are suppressed, and the precision of the direct current bias voltage can be further improved by carefully designing a circuit board and other measures. However, this results in a great increase in complexity of circuit design, an increase in product design time, and an increase in cost of the circuit, which is very uneconomical; and because the use condition of the special integrated operational amplifier is limited, the circuit has poor adaptability.
Disclosure of Invention
The invention aims to solve the technical problems that: in order to overcome the defects of the existing sine wave signal superposition direct current bias voltage method, the invention provides a device for applying direct current bias voltage to an alternating current sine wave signal source.
The technical scheme adopted by the invention is as follows: a device for applying DC bias voltage to AC sine wave signal source comprises a first signal source, a second signal source, a first capacitor, a second capacitor, a first source resistor, a second source resistor, a first resistor, a second resistor, a third resistor, a feedback resistor, a balance resistor, a measured piece, a first integrated operational amplifier, a second integrated operational amplifier and an inverter; the first integrated operational amplifier, the first resistor, the third resistor, the feedback resistor and the balance resistor form a deep negative feedback by taking the first integrated operational amplifier as a core to form a proportional amplifier; the second integrated operational amplifier, the second source resistor, the second resistor and the second capacitor form a deep negative feedback by taking the second integrated operational amplifier as a core to form an integrator.
In the alternating current equivalent circuit, the proportional amplifier, the integrator and the inverter form deep negative feedback by taking the proportional amplifier as a core, and the output of the first signal source after the amplitude of the first signal source is amplified by the proportional amplifier is used as an output alternating current sine wave signal of the alternating current-direct current signal source.
In the direct current equivalent circuit, the integrator, the inverter and the proportional amplifier form deep negative feedback by taking the integrator as a core, so that the virtual short is established, the potential of the non-inverting input end and the potential of the inverting input end of the second integrated operational amplifier are equal, the direct current voltage of the output end of the signal source is equal to the output direct current voltage of the second signal source, and then the direct current bias voltage signal is superimposed to the output end of the alternating current sine wave signal source and is used as the direct current bias voltage signal of the output of the alternating current and direct current signal source.
Further, the infinite integral result of the integrator on the alternating current sine wave signal is zero, so that the influence of the alternating current sine wave signal on the direct current bias voltage is eliminated.
Furthermore, the output end of the first integrated operational amplifier is provided with the current expansion circuit, so that the output current intensity of the direct-current bias voltage can be improved, and the load capacity of the direct-current bias voltage can be enhanced.
Still further, the present invention: the first signal source is an alternating current sine wave signal source, the second signal source is a direct current bias voltage signal source, the first capacitor is a coupling capacitor, the first source resistor is an alternating current sine wave signal source output resistor, the second source resistor is a direct current bias signal source output resistor, the second capacitor is an integrating capacitor, the first resistor is an input resistor of the integrated operational amplifier, the second resistor is an input resistor of the second integrated operational amplifier, the third resistor is an output resistor of the inverter, the feedback resistor is a negative feedback resistor of the first integrated operational amplifier, and the balance resistor is an in-phase input resistor of the first integrated operational amplifier.
The beneficial effects of the invention are as follows: based on the principle that the integrated operational amplifier forms a depth negative feedback circuit, the principle that the infinite integral result of an integrator to an alternating current sine wave signal is zero is utilized, and the common high-precision integrated operational amplifier is adopted to accurately superimpose direct current bias voltage on a sine wave signal source, so that an alternating current-direct current signal source is formed. The circuit has the advantages of simple and reliable structure, low overall complexity of the circuit, easy popularization and good application prospect.
Drawings
The invention will be further described with reference to the drawings and examples.
FIG. 1 is a schematic diagram of a direct superposition method;
FIG. 2 is a schematic diagram of an indirect superposition method;
FIG. 3 is a circuit diagram of the device of the present invention;
FIG. 4 is an equivalent circuit diagram of the AC power supply of the device of the present invention;
fig. 5 is a dc equivalent circuit diagram of the device of the present invention;
FIG. 6 is a schematic diagram of sine wave integration;
fig. 7 is a simplified diagram of an ac equivalent circuit of the device of the present invention.
Detailed Description
The invention will now be described in further detail with reference to the drawings and a preferred embodiment. The drawings are simplified schematic representations which merely illustrate the basic structure of the invention and therefore show only the structures which are relevant to the invention.
As shown in fig. 3, an apparatus for applying a dc bias voltage to an ac sine wave signal source includes an ac sine wave signal source Vs1, a dc bias voltage signal source Vs2, a source resistor Rs1, a source resistor Rs2, a coupling capacitor C1, an integrating capacitor C2, a resistor R1, a resistor R2, a resistor R3, a feedback resistor Rf1, a balancing resistor Rp, a device under test DUT, an integrated operational amplifier U1, an integrated operational amplifier U2, and an inverter U3.
One end of an alternating current sine wave signal source Vs1 is connected with one end of a source resistor Rs1, the other end of the alternating current sine wave signal source Vs1 is connected with the reference ground, the other end of the source resistor Rs1 is connected with one end of a coupling capacitor C1, the other end of the coupling capacitor C1 is connected with a resistor R1, the other end of the resistor R1 is connected with one end of a feedback resistor Rf1 and the inverting input end of an integrated operational amplifier U1, the other end of the balancing resistor Rp is connected with the reference ground, the output end of the integrated operational amplifier U1 is connected with the other end of a feedback resistor Rf1, one end of a resistor R2 and one end of a measured piece DUT, the other end of the resistor R2 is connected with the inverting input end of the integrated operational amplifier U2 and one end of the integrating capacitor C2, the other end of the measured piece DUT is connected with the reference ground, the non-inverting input end of the integrated operational amplifier U2 is connected with one end of the source resistor Rs2, the other end of the source resistor Rs2 is connected with the inverting input end of the direct current bias voltage signal source Vs2, the positive polarity end of the direct current bias voltage source Vs2 is connected with the reference ground, the other end of the output end of the integrated operational amplifier U2 is connected with the negative polarity of the output end of the integrated operational voltage source 3 One end of the resistor R 3 The other end of the first transistor is connected with the inverting input end of the integrated operational amplifier U1.
The alternating current sine wave signal source Vs1 generates an alternating current sine wave signal, and the direct current bias voltage signal source Vs2 generates a direct current bias voltage signal; the integrated operational amplifier U1 is used as a core to form deep negative feedback, and the resistor R1, the feedback resistor Rf1, the balance resistor Rp and the integrated operational amplifier U1 form a proportional amplifier; the integrated operational amplifier U2 is used as a core to form deep negative feedback, and the resistor R2, the integrating capacitor C2, the source resistor Rs2, the direct-current bias voltage signal source Vs2 and the integrated operational amplifier U2 form an integrator.
As shown in fig. 4, the ac equivalent circuit outputs an output signal of the ac sine wave signal source Vs1 amplified by the proportional amplifier as an output ac sine wave signal of the ac-dc signal source.
As shown in fig. 5, the dc equivalent circuit is formed by the fact that the integrated operational amplifier U2 is virtually short, and the potential of the non-inverting input terminal and the potential of the inverting input terminal of the integrated operational amplifier U2 are equal, so that the dc voltage of the output terminal of the signal source is equal to the output dc voltage of the second dc bias voltage signal source Vs2, and then the dc bias voltage signal is superimposed on the output terminal of the ac sine wave signal source, and is used as the dc bias voltage signal of the output of the ac dc signal source.
Since the infinite integration result of the integrator on the alternating current sine wave signal is zero, the alternating current sine wave signal at the output end of the signal source has no influence on the direct current bias voltage, and the direct current bias voltage signal is equal to the output direct current voltage of the second signal source, so that an alternating current-direct current signal source is formed.
Working principle:
let the output Vs 1=asin (wt) of the ac sine wave signal generated by the first signal source Vs1, a be the amplitude of the sine wave, w be the angular frequency of the sine wave, and the dc bias voltage signal generated by the second signal source Vs2 be Vs 2=vdc; rs1 is the internal resistance of the first signal source Vs1, and Rs2 is the internal resistance of the second signal source Vs 2.
The alternating current equivalent circuit of the invention is arranged at a voltage sampling point A, as shown in figure 4, the alternating current output generated by an alternating current sine wave signal is Uac, the voltage of the output end of the second integrated operational amplifier U2 is U2o,
because the resistor R2, the capacitor C2 and the integrated operational amplifier form an integrator, the non-inverting input end of the integrated operational amplifier U2 is grounded through the resistor, and U2 P ＝U2 N =0 is "virtual ground".
In the circuit, the current i in the capacitor C2 c2 Equal to the current i flowing through the resistor R2 R2 I.e. i c2 ＝i R2 ，
Output voltage U2o of U2 and voltage U on capacitor C2 C2 Is U2 o=u C2 Therefore, it is
At t 1 To t 2 The integral value of the time period is
U2o (t) 1 ) For the output voltage at the start of integration, here zero, the integrated final voltage is t 2 Output voltage at time.
When from t 1 To t 2 When the time is infinitely long, the time is long,
as shown in fig. 6, the meaning of integration is the sum of areas of the products of amplitude and time, and since the sine wave is symmetric up and down on the time axis, the infinitely long-time integration equivalent area is zero.
Thus, the integration of the sine wave signal in practical application of the invention is equivalent to infinite long-time ≡integration,
further available, the inverter output equivalent voltage is zero,
the ac equivalent circuit of the present invention can be further simplified, as shown in figure 7,
thus, the AC output generated by the AC sine wave signal is
Since the result of infinite integration of the ac sine wave signal by the integrator is zero, the dc equivalent circuit of the present invention sets the dc voltage output from the voltage sampling point a to Udc as shown in fig. 5.
Because the integrated operational amplifier U1, the integrated operational amplifier U2, the inverter U3, the resistor R1, the resistor R2, the feedback resistor Rf1 and the capacitor C2 form a deep negative feedback by the integrated operational amplifier U2,
so for the integrated operational amplifier U2, the false short holds, the inverting input terminal voltage U2 of the integrated operational amplifier U2 N With in-phase input voltage U2 P The values of the two are equal to each other,
then U2 N ＝U2 P ＝Vs2＝Vdc……(6)
According to the depth feedback, when the circuit is balanced, the direct current flowing through the resistor R2 is zero, and then the direct current bias voltage of the alternating current-direct current signal source is obtained to be udc=U2 N ＝Vs2＝Vdc…(7)
Further, the output U of the AC/DC signal source is
In summary, the method and the device for applying the dc bias voltage to the ac sine wave signal source form the deep negative feedback circuit based on the integrated operational amplifier, and precisely superimpose the dc bias voltage on the sine wave signal source to form the ac-dc signal source by utilizing the principle that the infinite integral result of the integrator on the ac sine wave signal is zero.
The foregoing description is merely illustrative of specific embodiments of the invention, and the invention is not limited to the details shown, since modifications and variations of the foregoing embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention.
Claims (6)
1. An apparatus for applying a dc bias voltage to an ac sine wave signal source, comprising: the device comprises a first signal source, a second signal source, a first capacitor, a second capacitor, a first source resistor, a second source resistor, a first resistor, a second resistor, a third resistor, a feedback resistor, a balance resistor, a measured piece, a first integrated operational amplifier, a second integrated operational amplifier and an inverter; the first integrated operational amplifier, the first resistor, the third resistor, the feedback resistor and the balance resistor form a deep negative feedback by taking the first integrated operational amplifier as a core to form a proportional amplifier; the second integrated operational amplifier, the second source resistor, the second resistor and the second capacitor form a deep negative feedback by taking the second integrated operational amplifier as a core to form an integrator;
one end of the first signal source is connected with one end of the first source resistor, the other end of the first signal source is connected with the reference ground, the other end of the first source resistor is connected with one end of the first capacitor, the other end of the first capacitor is connected with one end of the first resistor, the other end of the first resistor is connected with one end of the feedback resistor and the inverting input end of the first integrated operational amplifier, the non-inverting input end of the first integrated operational amplifier is connected with one end of the balancing resistor, the other end of the balancing resistor is connected with the reference ground, the output end of the first integrated operational amplifier is connected with the other end of the feedback resistor, one end of the second resistor and one end of the DUT, the other end of the second resistor is connected with the inverting input end of the second integrated operational amplifier and one end of the second capacitor, the other end of the DUT is connected with the reference ground, the non-inverting input end of the second integrated operational amplifier is connected with the positive polarity end of the second signal source, the negative polarity end of the second signal source is connected with the reference ground, the output end of the second integrated operational amplifier is connected with the other end of the inverting input end of the third resistor, and the other end of the inverting input end of the third resistor is connected with the first integrated operational amplifier.
2. The apparatus for applying a dc bias voltage to an ac sine wave signal source of claim 1, wherein: in the alternating current equivalent circuit, a proportional amplifier, an integrator and an inverter form deep negative feedback by taking the proportional amplifier as a core, and the output of the first signal source after the amplitude of the first signal source is amplified by the proportional amplifier is used as an output alternating current sine wave signal of the alternating current-direct current signal source.
3. The apparatus for applying a dc bias voltage to an ac sine wave signal source of claim 1, wherein: in the DC equivalent circuit, the integrator, the inverter and the proportional amplifier form a deep negative feedback by taking the integrator as a core, the virtual short is established, the potential of the in-phase input end and the potential of the opposite-phase input end of the second integrated operational amplifier are equal, the DC voltage of the output end of the signal source is equal to the output DC voltage of the second signal source, and then the DC bias voltage signal is superposed to the output end of the AC sine wave signal source and is used as the output DC bias voltage signal of the AC-DC signal source.
4. A device for applying a dc bias voltage to an ac sine wave signal source as claimed in claim 2 or 3, wherein: the integrator has zero infinite integration of the ac sine wave signal.
5. The apparatus for applying a dc bias voltage to an ac sine wave signal source of claim 1, wherein: and a current spreading circuit is arranged at the output end of the first integrated operational amplifier.
6. The apparatus for applying a dc bias voltage to an ac sine wave signal source of claim 1, wherein: the first signal source is an alternating current sine wave signal source, the second signal source is a direct current bias voltage signal source, the first capacitor is a coupling capacitor, the first source resistor is an alternating current sine wave signal source output resistor, the second source resistor is a direct current bias signal source output resistor, the second capacitor is an integrating capacitor, the first resistor is an input resistor of the first integrated operational amplifier, the second resistor is an input resistor of the second integrated operational amplifier, the third resistor is an output resistor of the inverter, the feedback resistor is a negative feedback resistor of the first integrated operational amplifier, and the balance resistor is an in-phase input resistor of the first integrated operational amplifier.
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| CN108845167B (en) * | 2018-04-15 | 2021-01-05 | 武汉市整流器研究所 | Large current generator device |
| JP7094190B2 (en) * | 2018-10-16 | 2022-07-01 | 日置電機株式会社 | How to adjust the negative feedback circuit in the impedance measuring device and the impedance measuring device |
| CN113589129B (en) * | 2021-08-18 | 2022-06-21 | 金华高等研究院 | Measuring device and measuring method for C-V curve of avalanche photodiode |
| CN115389797B (en) * | 2022-08-29 | 2023-07-25 | 北京东方计量测试研究所 | AC/DC superimposed voltage source for spacecraft DC load input impedance measurement |
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