CN208271054U - A kind of precision constant current source based on differential amplifier and feedback buffer - Google Patents
A kind of precision constant current source based on differential amplifier and feedback buffer Download PDFInfo
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- CN208271054U CN208271054U CN201820990105.XU CN201820990105U CN208271054U CN 208271054 U CN208271054 U CN 208271054U CN 201820990105 U CN201820990105 U CN 201820990105U CN 208271054 U CN208271054 U CN 208271054U
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Abstract
The utility model discloses a kind of precision constant current source based on differential amplifier and feedback buffer, including differential amplifier, feedback buffer, triode T2, the resistance R for integrating amplifier, input resistance and feedback resistancerefWith resistance Rload, the positive input terminal of differential amplifier is connected with reference voltage output circuit, and the SENSE terminals of negative input end ground connection, the base stage of the output end connecting triode T2 of differential amplifier, the emitter connection differential amplifier of triode T2 are simultaneously sequentially connected in series resistance RrefWith resistance RloadAfter be grounded, the output end and negative input end of the Voltage Feedback input terminal of differential amplifier and feedback buffer connect, resistance RrefWith resistance RloadBetween node and feedback buffer positive input terminal connect.The utility model improves the consistency between peripheral resistance using differential amplifier, and electric current output loop and voltage feedback loop is isolated using feedback buffer, improves the input impedance of differential amplifier opposite outer, the electric current for exporting constant-current source is more accurate.
Description
Technical field
The utility model relates to precision constant current source technical fields, are a kind of based on differential amplifier and feedback specifically
The precision constant current source of buffer.
Background technique
Many applications require precision constant current source, including industrial stokehold, instrument and meter, Medical Devices and consumption
Electronic product etc..For example, Process Control System utilizes exciting current needed for constant-current source offer resistance temperature detector；Number
Multimeter utilizes constant-current source measurement resistance, capacitor and diode；The long range information transmission system drives communication using constant-current source
Current loop.The quality of constant-current source directly decides the overall performance of these systems.Conventional constant current source all uses operation substantially
Amplifier, resistance and the building of other discrete devices, traditional controlled constant-current source circuit is as shown in Figure 1, NPN triode work is being satisfied
And area, using amplifier feed-back come steady load electric current.Concept according to ideal amplifier " empty short " with " void is disconnected ", can derive negative
Current-carrying calculation formula, is shown below: Io=Vref1× ﹙ Rf2÷Rg2+ ﹙ Rf1÷Rg1﹚ × ﹙ Rf2÷Rg2﹚ ﹚ ÷ ﹙ Rref1﹙ Rf2
÷Rg2+ 1 ﹚+Rload1﹙ Rf2÷Rg2-Rf1÷Rg1﹚ ﹚, if Rg1=Rg2=Rf1=Rf2, above formula can simplify are as follows: Io=Vref1÷
Rref1, process is shifted onto it is found that influencing traditional voltage controlled current source precision and temperature drift according to above load current calculating formula
Principal element have: input pickup resistance Rg1, input pickup resistance Rg2, feedback resistance Rf1, feedback resistance Rf2Consistency, amplifier
The input impedance and temperature drift of opposite outer and reference resistance Rref1, reference voltage Vref1Precision and temperature stability.
Utility model content
The purpose of this utility model is to provide a kind of precision constant current source based on differential amplifier and feedback buffer, use
In solving, the tradition voltage controlled current source due to caused by the input impedance of the consistency of resistance and amplifier is high in the prior art is smart
Spend not high problem.
The utility model is solved the above problems by following technical proposals:
A kind of precision constant current source based on differential amplifier and feedback buffer, including by amplifier, input resistance and anti-
Differential amplifier, feedback buffer, triode T2, the resistance R that feed resistance integratesrefWith resistance Rload, the differential amplification
The positive input terminal of device is connected with reference voltage output circuit, the negative input end ground connection of differential amplifier, the output of differential amplifier
End connects the base stage of the triode T2, the emitter of triode T2 connect the SENSE terminals of the differential amplifier and according to
The secondary series connection resistance RrefWith resistance RloadAfter be grounded, the Voltage Feedback input terminal of differential amplifier and the feedback buffer
Output end and negative input end connection, resistance RrefWith resistance RloadBetween node and feedback buffer positive input terminal connect
It connects.
Principle:
The integrated technology of the differential amplifier that amplifier, input resistance and feedback resistance are integrated, chip-scale can be big
Amplitude improves the consistency between resistance.In order to improve the input impedance of differential amplifier opposite outer, in resistance RrefAnd resistance
RloadBetween node and Voltage Feedback input terminal increase feedback buffer, electric current output loop and Voltage Feedback can be isolated and return
Road reduces the input impedance of differential amplifier voltage feedback end.Therefore, using the pressure based on differential amplifier and feedback buffer
Control constant-current source circuit solves the consistency of resistance and the input of feedback buffer reduction differential amplifier in differential amplifier
Under impedance, high precise current source can be obtained.
Preferably, the differential amplifier includes amplifier OP2 and the resistance R integrated with the amplifier OP2g11、
Resistance Rf11, resistance Rg22With resistance Rf22, the resistance Rg11First end, resistance Rf11First end be separately connected amplifier OP2
Negative input end and positive input terminal, resistance Rg11Second end ground connection, resistance Rf11Second end and the reference voltage output electricity
Road connection, the resistance Rg22One end connect with the negative input end of amplifier OP2, resistance Rg22The other end and the SENSE
Terminals connection, the resistance Rf22One end connect with the positive input terminal of amplifier OP2, the other end and the Voltage Feedback are defeated
Enter end connection.
Resistance Rg11, resistance Rf11Respectively as the input pickup resistance of differential amplifier, resistance Rg22With resistance Rf22As anti-
Feed resistance, is integrated in chip piece with differential amplifier, the integrated technology of chip-scale can increase substantially the consistency between resistance.
Preferably, the reference voltage output circuit includes sequentially connected control chip, digital analog converter, operation amplifier
Device, the output end of the operational amplifier are connect with the positive input terminal of the differential amplifier.
Chip is controlled as control centre to lead to using microprocessor STM32F103CBT6 by SPI and digital analog converter
Letter is connected, and can control the size of precision constant current source circuit output current.Digital analog converter is turned using the simulation of 16 bit digital of low-power consumption
Parallel operation AD5664, digital analog converter are connect with operational amplifier, and operational amplifier selects precision, micro energy lose, low noise, COMS rail
To rail operational amplifier AD8603, it is rail-to-rail between digital analog converter AD5664 and difference amplifier to also use COMS
Operational amplifier AD8603 is isolated, and ensure that outputting reference voltage VrefPrecision.Differential amplifier selection low excursion with temperature,
The unit gain difference amplifier AD8276 of low-power consumption has good temperature stability, inhibits temperature drift.
It preferably, further include being mentioned for the triode T2, differential amplifier, feedback buffer and reference voltage input circuit
The power circuit of voltage supplied.
Preferably, the power circuit includes CMOS linear voltage regulator, the voltage input end of the CMOS linear voltage regulator
It is connect after connection filter circuit with battery, the voltage output end of CMOS linear voltage regulator exports electricity with the reference voltage respectively
The collector connection on road, differential amplifier, the voltage input end of feedback buffer and triode T2.
Power circuit is using low noise, the CMOS linear voltage regulator ADP7104 of high stable, by 9~12V's of battery input
Input voltage is converted to the output voltage of+5V, is that triode T2, differential amplifier, feedback buffer and reference voltage input electricity
Road provides operating voltage.
The utility model compared with prior art, have the following advantages that and the utility model has the advantages that
(1) the utility model improves the consistency between peripheral resistance using differential amplifier, is isolated using feedback buffer
Electric current output loop and voltage feedback loop improve the input impedance of differential amplifier opposite outer, the electricity for exporting constant-current source
It is more accurate to flow.
(2) the utility model uses microcontroller embedded technology and digital simulation switch technology, can pass through external signal tune
The size of whole precision constant current source output electric current.
(3) device that the utility model has selected low noise, low-power consumption, low excursion with temperature, size small, reduces constant-current source
The temperature drift for exporting electric current, reduces the size of whole system, has size small, and precision is high, and temperature stability is good, and number connects
The advantages that mouth is convenient to use.
Detailed description of the invention
Fig. 1 is traditional controlled constant-current source circuit figure based on amplifier；
Fig. 2 is the circuit diagram of the first specific embodiment in the utility model；
Fig. 3 is the circuit diagram of second of specific embodiment in the utility model.
Specific embodiment
The utility model is described in further detail below with reference to embodiment, but the embodiments of the present invention is not
It is limited to this.
Embodiment 1:
In conjunction with shown in attached drawing 1, a kind of precision constant current source based on differential amplifier and feedback buffer, including will amplify
Differential amplifier U1 that device, input resistance and feedback resistance integrate, feedback buffer U3, triode T2, resistance RrefAnd electricity
Hinder Rload, the positive input terminal of the differential amplifier U1 is connected with reference voltage output circuit U2, and bearing for differential amplifier U1 is defeated
Enter end ground connection, the output end of differential amplifier U1 connects the base stage of the triode T2, described in the emitter connection of triode T2
The SENSE terminals of differential amplifier U1 are simultaneously sequentially connected in series the resistance RrefWith resistance RloadAfter be grounded, differential amplifier U1's
Voltage Feedback input terminal is connect with the output end of the feedback buffer U3 and negative input end, resistance RrefWith resistance RloadIt
Between node connect with the positive input terminal of feedback buffer U3.The differential amplifier U1 includes amplifier OP2 and puts with described
Big device OP2 integrated resistance Rg11, resistance Rf11, resistance Rg22With resistance Rf22, the resistance Rg11First end, resistance Rf11
First end be separately connected the negative input end and positive input terminal of amplifier OP2, resistance Rg11Second end ground connection, resistance Rf11?
Two ends are connect with the reference voltage output circuit, the resistance Rg22One end connect with the negative input end of amplifier OP2, electricity
Hinder Rg22The other end connect with the SENSE terminals, the resistance Rf22One end and amplifier OP2 positive input terminal connect
It connects, the other end is connect with the Voltage Feedback input terminal.
Principle:
By resistance Rg11, resistance Rf11Respectively as the input pickup resistance of differential amplifier U1, resistance Rg22With resistance Rf22Make
For feedback resistance, chip piece is integrated in differential amplifier U1 and forms differential amplifier U1, the integrated technology of chip-scale can be big
Amplitude improves the consistency between resistance.In order to improve the input impedance of differential amplifier opposite outer, in resistance RrefAnd resistance
RloadBetween node and Voltage Feedback input terminal increase feedback buffer U3, electric current output loop and Voltage Feedback can be isolated
Circuit reduces the input impedance of differential amplifier U1 pressure feedback port.Therefore, using based on differential amplifier and feedback buffer
Controlled constant-current source circuit reduce differential amplification in the consistency U1 and feedback buffer U3 that differential amplifier solves resistance
Under the input impedance of device U1, high precise current source can be obtained.
Embodiment 2:
On the basis of embodiment 1, as shown in connection with fig. 2, the reference voltage output circuit U2 includes sequentially connected control
Coremaking piece U21, digital analog converter U22, operational amplifier U23, the output end of the operational amplifier U23 and the differential amplification
The positive input terminal of device U1 connects.For the triode T2, differential amplifier U1, feedback buffer U3 and reference voltage input circuit
The power circuit that U2 provides voltage includes CMOS linear voltage regulator U4, the voltage input end connection of the CMOS linear voltage regulator U4
Connect after filter circuit with battery, the voltage output end of CMOS linear voltage regulator U4 respectively with the reference voltage output circuit
The collector connection of U2, differential amplifier U1, the voltage input end of feedback buffer U3 and triode T2.
Power circuit is using low noise, the CMOS linear voltage regulator ADP7104 of high stable, by 9~12V's of battery input
Input voltage is converted to the output voltage of+5V, is that triode T2, differential amplifier U1, feedback buffer U3 and reference voltage are defeated
Enter circuit U 2 and operating voltage is provided.Control chip U21 is passed through as control centre using microprocessor STM32F103CBT6
SPI is connected with digital analog converter U22 communication, can control the size of precision constant current source circuit output current.Digital analog converter U22 is adopted
It is connect with 16 bit digital analog converter AD5664 of low-power consumption, digital analog converter U22 with operational amplifier U23, operational amplifier
U23 selects precision, micro energy lose, low noise, the rail-to-rail operational amplifier AD8603 of COMS, in digital analog converter AD5664 and
The rail-to-rail operational amplifier AD8603 of COMS is also used between difference amplifier U1 to be isolated, and ensure that outputting reference voltage
VrefPrecision.Differential amplifier U1 selects the unit gain difference amplifier AD8276 of low excursion with temperature, low-power consumption, has good
Good temperature stability inhibits temperature drift.The utility model uses microcontroller embedded technology and digital simulation switch technology,
The size that precision constant current source exports electric current can be adjusted by external signal, select low noise, low-power consumption, low excursion with temperature, ruler
Very little small device, reduces the temperature drift of constant current source output current, reduces the size of whole system, has size small, essence
The advantages that degree is high, and temperature stability is good, and digital interface is easy to use.
Although reference be made herein to the utility model is described in the explanatory embodiment of the utility model, above-described embodiment
The only preferable embodiment of the utility model, the embodiments of the present invention are simultaneously not restricted to the described embodiments, it should
Understand, those skilled in the art can be designed that a lot of other modification and implementations, these modifications and implementations will be fallen
Within scope and spirit disclosed in the present application.
Claims (5)
1. a kind of precision constant current source based on differential amplifier and feedback buffer, which is characterized in that including by amplifier, input
Differential amplifier (U1) that resistance and feedback resistance integrate, feedback buffer (U3), triode T2, resistance RrefAnd resistance
Rload, the positive input terminal of the differential amplifier (U1) is connected with reference voltage output circuit (U2), differential amplifier (U1)
Negative input end ground connection, the output end of differential amplifier (U1) connect the base stage of the triode T2, and the emitter of triode T2 connects
It connects the SENSE terminals of the differential amplifier (U1) and is sequentially connected in series the resistance RrefWith resistance RloadAfter be grounded, it is differential to put
The Voltage Feedback input terminal of big device (U1) is connect with the output end of the feedback buffer (U3) and negative input end, resistance Rref
With resistance RloadBetween node connect with the positive input terminal of feedback buffer (U3).
2. a kind of precision constant current source based on differential amplifier and feedback buffer according to claim 1, feature exist
In the differential amplifier (U1) includes amplifier OP2 and the resistance R integrated with the amplifier OP2g11, resistance Rf11、
Resistance Rg22With resistance Rf22, the resistance Rg11First end, resistance Rf11First end be separately connected the negative input of amplifier OP2
End and positive input terminal, resistance Rg11Second end ground connection, resistance Rf11Second end connect with the reference voltage output circuit, institute
State resistance Rg22One end connect with the negative input end of amplifier OP2, resistance Rg22The other end and the SENSE terminals connect
It connects, the resistance Rf22One end connect with the positive input terminal of amplifier OP2, the other end is connect with the Voltage Feedback input terminal.
3. a kind of precision constant current source based on differential amplifier and feedback buffer according to claim 1 or 2, feature
It is, the reference voltage output circuit (U2) includes sequentially connected control chip (U21), digital analog converter (U22), operation
The output end of amplifier (U23), the operational amplifier (U23) is connect with the positive input terminal of the differential amplifier (U1).
4. a kind of precision constant current source based on differential amplifier and feedback buffer according to claim 3, feature exist
In further including being mentioned for the triode T2, differential amplifier (U1), feedback buffer (U3) and reference voltage input circuit (U2)
The power circuit of voltage supplied.
5. a kind of precision constant current source based on differential amplifier and feedback buffer according to claim 4, feature exist
In the power circuit includes CMOS linear voltage regulator (U4), the voltage input end connection of the CMOS linear voltage regulator (U4)
Connect after filter circuit with battery, the voltage output end of CMOS linear voltage regulator (U4) respectively with the reference voltage output circuit
(U2), the collector connection of differential amplifier (U1), the voltage input end of feedback buffer (U3) and triode T2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820990105.XU CN208271054U (en) | 2018-06-26 | 2018-06-26 | A kind of precision constant current source based on differential amplifier and feedback buffer |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820990105.XU CN208271054U (en) | 2018-06-26 | 2018-06-26 | A kind of precision constant current source based on differential amplifier and feedback buffer |
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| CN208271054U true CN208271054U (en) | 2018-12-21 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108508955A (en) * | 2018-06-26 | 2018-09-07 | 中国工程物理研究院化工材料研究所 | A kind of precision constant current source based on differential amplifier and feedback buffer |
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2018
- 2018-06-26 CN CN201820990105.XU patent/CN208271054U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108508955A (en) * | 2018-06-26 | 2018-09-07 | 中国工程物理研究院化工材料研究所 | A kind of precision constant current source based on differential amplifier and feedback buffer |
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