A low-noise high-precision triode current source

Abstract

The application discloses a low-noise high-precision triode current source, which comprises a current source filter noise reduction circuit, an output voltage adjustment and calibration circuit and a voltage source to current source circuit connected in sequence, wherein the output voltage adjustment and calibration circuit comprises a digital-to-analog converter, a PC end, a resistor R3, a resistor R4, a resistor network, a second operational amplifier and a third operational amplifier; the output end of the PC end is connected with the input end of the digital-to-analog converter; the output end of the digital-to-analog converter is connected with the inverting input end of the third operational amplifier; the non-inverting input end of the third operational amplifier is connected with the non-inverting input end of the second operational amplifier through a relay K2; and the output end of the third operational amplifier is connected with the input end of the PC end. The triode current source provided by the application has low low-frequency noise, high output current precision and stable output current, and can effectively reduce the low-frequency noise of a magnetic field when the current source is used to supply power to a magnetic field coil.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of quantum precision measurement, and particularly relates to a low-noise high-precision triode current source. BACKGROUND

[0002] The battery is used to supply power to the magnetic field coil, which can effectively reduce the low-frequency noise of the magnetic field, and is the lowest noise method at present; however, the noise level of the battery and the output current will change with the discharge of the battery, and the noise of the battery output current will increase when the battery has low power, so that the magnetic field strength drifts, and therefore the experiment cannot be performed for a long time, and the characteristics of the battery make it impossible to be connected with the PC end for programming and remote control, and it is very inconvenient to adjust the output current or voltage during the experiment.

[0003] The ordinary commercial current source is used to supply power to the magnetic field coil, which will introduce large low-frequency noise. In quantum precision measurement experiments such as measuring the Larmor frequency of atoms, the low-frequency noise of the battery will drown the relevant information of the atoms, which leads to the failure of the experiment.

[0004] There are also professional commercial low-noise current sources on the market, but such low-noise current sources are often expensive, and the application cost is high, and there is still large low-frequency noise in quantum precision measurement experiments. Moreover, the better low-noise current sources on the market cannot be imported from abroad. SUMMARY

[0005] According to the deficiencies of the prior art, the present application provides a low-noise high-precision triode current source, which has low low-frequency noise, high output current precision, and stable output current source. The low-frequency noise of the magnetic field can be effectively reduced by using the current source to supply power to the magnetic field coil.

[0006] In order to solve the above technical problems, the technical scheme of the present application is as follows:

[0007] A low-noise, high-precision transistor current source includes a current source filtering and noise reduction circuit, an output voltage adjustment and calibration circuit, and a voltage source to current source circuit connected in sequence. The output voltage adjustment and calibration circuit includes a digital-to-analog converter (DAC), a PC terminal, resistors R3 and R4, a resistor network, a second operational amplifier, and a third operational amplifier. The output terminal of the PC terminal is connected to the input terminal of the DAC, and the output terminal of the DAC is connected to the inverting input terminal of the third operational amplifier. The non-inverting input terminal of the third operational amplifier is connected to the non-inverting input terminal of the second operational amplifier via relay K2. The output terminal of the third operational amplifier is connected to the input terminal of the PC terminal. One end of resistors R3 and R4 is connected to the two ends of the resistor network, and one end of resistor R4 is connected to the non-inverting input terminal of the second operational amplifier via relay K2. The inverting input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier is connected to the voltage source to current source circuit. The output terminal of the current source filtering and noise reduction circuit is connected to the resistor network.

[0008] Preferably, the resistor network includes several resistors R1, resistors R2 and relay K1. The several resistors R1 are connected in series. The two ends of each resistor R1 are connected to one end of two resistors R2 respectively. The other end of each resistor R2 is connected to the output terminal of the current source filter noise reduction circuit through a relay K1.

[0009] Preferably, one of the resistors R1, R2 and K1 constitutes a first-order resistor unit, and the resistor network includes a plurality of first-order resistor units, the number of which is not less than 50.

[0010] Preferably, the current source filtering noise reduction circuit includes a current source, an inductor L1, a capacitor C1, and a first operational amplifier. The positive terminal of the current source is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the positive terminal of the capacitor C1 and the non-inverting input terminal of the first operational amplifier. The negative terminal of the current source is connected to the negative terminal of the capacitor C1 and grounded. The inverting input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier, and the output terminal of the first operational amplifier is connected to a relay K1.

[0011] Preferably, the current source is a 3.7V lithium battery.

[0012] Preferably, the capacitor C1 is a 3.8V, 10F supercapacitor.

[0013] Preferably, the voltage source to current source circuit includes transistors Q1 and Q2, potentiometer RP1, and resistor R5. The output terminal of the second operational amplifier is connected to the emitter of transistor Q1, the base of transistor Q1 is connected to the emitter of transistor Q2, the collector of transistor Q1 is connected to the base of transistor Q2, the two ends of potentiometer RP1 are connected to the base and emitter of transistor Q1 respectively, one end of resistor R5 is connected to the collector of transistor Q1, and the other end of resistor R5 is connected to the negative terminal of the current source and grounded. The collector of transistor Q2 outputs circuit Iout.

[0014] Preferably, both transistors Q1 and Q2 are PNP type transistors.

[0015] This invention has the following characteristics and beneficial effects:

[0016] Using the above technical solution, the filter circuit adopts LC low-pass filtering; the LC low-pass filter circuit filters out the noise of the battery, and compared with the RC low-pass filter circuit, the LC low-pass filter circuit does not require impedance matching when connecting the chip.

[0017] Using transistors as the current output electrode, the low-frequency noise of transistors is negligible compared to the low-frequency noise of the chip; a voltage source to current source circuit composed of two transistors and a ladder resistor network allows the output current to be adjusted within the range of 0 to 80mA, and the output current can also be programmed and controlled by a computer.

[0018] This allows it to output current with lower noise than commercially available current sources in China.

[0019] The output current of the current source can be controlled by the PC, and the output current can be calibrated in real time through a negative feedback circuit to achieve stability of the power supply during long-term operation. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a circuit schematic diagram of an embodiment of the present invention.

[0022] In the diagram, 1 is the current source filter and noise reduction circuit; 2 is the output voltage adjustment and calibration circuit; 3 is the voltage source to current source circuit; 1-1 is the lithium battery; 1-2 is the first operational amplifier; 2-1 is the second operational amplifier; 2-2 is the third operational amplifier; 2-3 is the high-precision digital-to-analog converter; and 2-4 is the PC terminal. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] This invention provides a low-noise, high-precision transistor current source, such as... Figure 1 As shown, it includes a current source filter noise reduction circuit 1, an output voltage adjustment and calibration circuit 2, and a voltage source to current source circuit 3 connected in sequence.

[0027] Specifically, the current source filtering and noise reduction circuit 1 includes a current source 1-1, an inductor L1, a capacitor C1, and a first operational amplifier 1-2. The positive terminal of the current source 1-1 is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the positive terminal of the capacitor C1 and the non-inverting input terminal of the first operational amplifier 1-1. The negative terminal of the current source 1-1 is connected to the negative terminal of the capacitor C1 and grounded. The inverting input terminal of the first operational amplifier 1-2 is connected to the output terminal of the first operational amplifier, and the output terminal of the first operational amplifier 1-2 is connected to a relay K1.

[0028] In this embodiment, the first operational amplifier is an LT1028, capacitor C1 is a 3.8V, 10F supercapacitor, and the current source is a 3.7V lithium battery. The output of the lithium battery first passes through an LC low-pass filter for noise reduction. The LC corner frequency is very low, and the LT1028 is used as the output stage to output the lithium battery voltage.

[0029] In the above technical solution, the current source filtering and noise reduction circuit uses an LC low-pass filter; the LC low-pass filter circuit filters out the battery noise. It is understandable that, compared to an RC low-pass filter circuit, the LC low-pass filter circuit does not require impedance matching when connected to a subsequent chip.

[0030] In a further configuration of this embodiment, the output voltage adjustment and calibration circuit 2 includes a digital-to-analog converter 2-3, a PC terminal 2-4, resistors R3 and R4, a resistor network, a second operational amplifier 2-1, and a third operational amplifier 2-2. The output terminal of the PC terminal 2-4 is connected to the input terminal of the digital-to-analog converter 2-3, and the output terminal of the digital-to-analog converter 2-3 is connected to the inverting input terminal of the third operational amplifier 2-2. The non-inverting input terminal of the third operational amplifier 2-2 is connected to the non-inverting input terminal of the second operational amplifier 2-1 via a relay K2. The output terminal of the third operational amplifier 2-3 is connected to the input terminal of the PC terminal. One end of resistors R3 and R4 is connected to the two ends of the resistor network, and one end of resistor R4 is connected to the non-inverting input terminal of the second operational amplifier 2-1 via a relay K2. The inverting input terminal of the second operational amplifier 2-1 is connected to the output terminal of the second operational amplifier 2-1. The output terminal of the second operational amplifier 2-1 is connected to the voltage source to current source circuit 3, and the output terminal of the current source filtering and noise reduction circuit 1 is connected to the resistor network.

[0031] Furthermore, the resistor network includes several resistors R1, resistors R2 and relay K1. The several resistors R1 are connected in series. The two ends of each resistor R1 are connected to one end of two resistors R2 respectively. The other end of each resistor R2 is connected to the output terminal of the current source filter noise reduction circuit through a relay K1.

[0032] Understandably, resistor R1, resistor R2, and relay K1 constitute a first-order resistor unit, and the resistor network includes several first-order resistor units.

[0033] In this embodiment, the resistance values ​​of resistors R3 and R4 are both 3650Ω, the resistance value of resistor R1 is 1440Ω, the resistance value of resistor R2 is 3650Ω, the second operational amplifier and the third operational amplifier are both LT1028, and the digital-to-analog converter is AD667KN.

[0034] In the above technical solution, when the output voltage needs to be adjusted or calibrated, the resistor network is connected to the third operational amplifier via relay K2. PC 2-4 controls the digital-to-analog converter 2-3 to output the required voltage to the inverting input of the third operational amplifier 2-2. The voltage output from the current source filter and noise reduction circuit 1 passes through the resistor network to the non-inverting input of the second operational amplifier 2-1. After comparison, the voltage is fed back to the PC. The PC adjusts relay K1 based on the difference. The switching state of each relay K1 and the voltage input to the non-inverting input of the second operational amplifier 2-1 are calculated using a successive approximation algorithm. It is understood that the more first-order resistor units in the resistor network, the more accurate the output voltage value. In this embodiment, the number of first-order resistor units is 50.

[0035] In a further embodiment, the voltage source to current source circuit 3 includes transistors Q1 and Q2, a potentiometer RP1, and a resistor R5. The output terminal of the second operational amplifier is connected to the emitter of transistor Q1, the base of transistor Q1 is connected to the emitter of transistor Q2, and the collector of transistor Q1 is connected to the base of transistor Q2. The two ends of the potentiometer RP1 are connected to the base and emitter of transistor Q1, respectively. One end of the resistor R5 is connected to the collector of transistor Q1, and the other end of the resistor R5 is connected to the negative terminal of the current source and grounded. The collector output circuit Iout of transistor Q2 is also included. Both transistors Q1 and Q2 are PNP transistors.

[0036] In this embodiment, transistors Q1 and Q2 are both S8550, potentiometer RP1 has a resistance of 50Ω, and resistor R5 has a resistance of 50Ω.

[0037] Understandably, a voltage source can be converted into a current source using voltage-to-current source circuit 3. The output current Iout satisfies a certain relationship with potentiometer RP1, and the output current can be coarsely adjusted by adjusting potentiometer RP1. Since the low-frequency noise of the transistor is negligible compared to that of the operational amplifier, there is no need to consider introducing additional low-frequency noise, ultimately achieving a low-noise, high-precision transistor current source output.

[0038] In the above technical solution, transistor Q2 is used as the current output electrode, and the low-frequency noise of transistor Q2 can be ignored compared with the low-frequency noise of the chip.

[0039] Understandably, a voltage-to-current source circuit composed of two transistors and a resistor network can be used to adjust the output current within the range of 0 to 80mA. The output current can also be programmed and controlled by a computer.

[0040] To demonstrate the effectiveness of the above technical solution, this embodiment targets an output current of 20mA. Tests showed that the power spectral densities at frequencies of 1Hz, 10Hz, and greater than 100Hz were 10... -17 10 -18 10 -19 A 2 / Hz, which shows that it can meet the needs of quantum precision measurement experiments.

[0041] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments, including components, without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A low-noise, high-precision transistor current source, characterized in that, The system includes a current source filtering and noise reduction circuit, an output voltage adjustment and calibration circuit, and a voltage source to current source circuit connected in sequence. The output voltage adjustment and calibration circuit includes a digital-to-analog converter (DAC), a PC terminal, resistors R3 and R4, a resistor network, a second operational amplifier, and a third operational amplifier. The output terminal of the PC terminal is connected to the input terminal of the DAC. The output terminal of the DAC is connected to the inverting input terminal of the third operational amplifier. The non-inverting input terminal of the third operational amplifier is connected to the non-inverting input terminal of the second operational amplifier via relay K2. The output terminal of the third operational amplifier is connected to the input terminal of the PC terminal. One end of resistors R3 and R4 is connected to both ends of the resistor network, and one end of resistor R4 is connected to the non-inverting input terminal of the second operational amplifier via relay K2. The other ends of resistors R3 and R4 are grounded. The inverting input terminal of the second operational amplifier is connected to its output terminal. The output terminal of the second operational amplifier is connected to the voltage source to current source circuit. The output terminal of the current source filtering and noise reduction circuit is connected to the resistor network. The voltage source to current source circuit includes transistors Q1 and Q2, potentiometer RP1, and resistor R5. The output terminal of the second operational amplifier is connected to the emitter of transistor Q1. The base of transistor Q1 is connected to the emitter of transistor Q2. The collector of transistor Q1 is connected to the base of transistor Q2. The two ends of potentiometer RP1 are connected to the base and emitter of transistor Q1, respectively. One end of resistor R5 is connected to the collector of transistor Q1, and the other end of resistor R5 is connected to the negative terminal of the current source and grounded. The collector of transistor Q2 outputs circuit Iout.

2. The low-noise, high-precision transistor current source according to claim 1, characterized in that, The resistor network includes several resistors R1, R2 and a relay K1. The resistors R1 are connected in series. The two ends of each resistor R1 are connected to one end of two resistors R2 respectively. The other end of each resistor R2 is connected to the output terminal of the current source filter noise reduction circuit through a relay K1. One end of the resistor network is connected to one end of resistor R3 and the other end of the resistor network is connected to one end of resistor R4.

3. The low-noise, high-precision transistor current source according to claim 2, characterized in that, The resistor R1, resistor R2 and relay K1 constitute a first-order resistor unit, and the resistor network includes a plurality of first-order resistor units, the number of which is not less than 50.

4. The low-noise, high-precision transistor current source according to claim 2, characterized in that, The current source filtering and noise reduction circuit includes a current source, an inductor L1, a capacitor C1, and a first operational amplifier. The positive terminal of the current source is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the positive terminal of the capacitor C1 and the non-inverting input terminal of the first operational amplifier. The negative terminal of the current source is connected to the negative terminal of the capacitor C1 and grounded. The inverting input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier, and the output terminal of the first operational amplifier is connected to a relay K1.

5. The low-noise, high-precision transistor current source according to claim 4, characterized in that, The current source is a 3.7V lithium battery.

6. The low-noise, high-precision transistor current source according to claim 4, characterized in that, The capacitor C1 is a supercapacitor with a rated voltage of 3.8V and a capacitance of 10F.

7. The low-noise, high-precision transistor current source according to claim 1, characterized in that, Both transistors Q1 and Q2 are PNP type transistors.

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