A high-precision multi-channel output reference voltage source circuit

Abstract

The present invention relates to the technical field of analog integrated circuits, and in particular to a high-precision multi-channel output reference voltage source circuit. The invention comprises: a startup circuit, which is composed of a resistor and a triode with a collector-base short circuit; after the circuit is powered on, the safe startup of the overall circuit is completed; a bias circuit, after the circuit is started, provides the required static current for each internal branch to ensure the normal operation of the overall circuit; a bandgap reference circuit, which is designed based on a Brokaw bandgap reference source model and serves as the core module of the reference voltage source circuit, provides a bandgap reference voltage with good temperature drift performance, and directly determines the temperature drift performance of the entire reference voltage circuit; an operational amplifier circuit, which serves as the core module of the reference voltage source circuit, ensures the output capacity of the overall circuit, amplifies the bandgap reference voltage, and realizes multi-channel high-precision voltage output, so as to solve the problem of a single reference voltage output for the traditional reference voltage circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of analog integrated circuits, and in particular to a high-precision multi-channel output reference voltage source circuit. Background Art

[0002] As a basic application circuit, the reference voltage source is widely used in digital circuits and analog circuits. In the early days, it was mainly used in a series of high-performance digital and analog integrated circuits such as ADC and DAC, and later gradually expanded to some large-scale integrated circuit applications. In order to improve product performance and reduce product size, the current mainstream high-performance reference voltage sources have only a fixed output voltage. In large-scale integrated circuit applications, one reference voltage is obviously not enough, and multiple different reference voltages are often required as references. Only multiple single-output reference voltage source circuits can be added to meet application requirements, which puts higher requirements on the use environment. Summary of the invention

[0003] The object of the present invention is to provide a reference voltage source circuit with high precision, low temperature drift and multiple outputs, so as to solve the problem that the traditional reference voltage circuit has a single output reference voltage.

[0004] In order to solve the above technical problems, the present invention provides a high-precision multi-output reference voltage source circuit, comprising:

[0005] The startup circuit is composed of a resistor and a transistor with the collector and base short-circuited. It is equivalent to setting a forward-biased diode and resistor between the power supply and the ground. The startup current can be generated at the moment of power-on, thereby starting the entire circuit. After the circuit is powered on, the safe startup of the entire circuit is completed.

[0006] The bias circuit shares some components with the startup circuit, adopts the form of transistor cross-coupling, combines with resistors to generate bias current, and provides the required bias current for each branch through the current mirror; after the circuit is started, it provides the required static current for each internal branch to ensure the normal operation of the overall circuit;

[0007] The bandgap reference circuit, as the core module of the reference voltage source circuit, provides a bandgap reference voltage with excellent temperature drift performance, which directly determines the temperature drift performance of the entire reference voltage circuit; based on the Brokaw bandgap reference source model design, the bases of two transistors of unequal areas are connected, and a resistor is connected in series between the emitters. Since the emitter area of ​​the transistor determines the size of its tube voltage drop, the voltage difference between the tube voltage drops of the two transistors falls on the resistor, which will generate a reference current and flow through the resistor connected in series with it. Therefore, a bandgap reference voltage is generated, which is composed of the tube voltage drop of the transistor and the voltage dropped on the resistor. At the same time, a laser adjustment scheme is designed in the bandgap reference circuit, which can perform post-correction on the temperature coefficient of the output reference voltage;

[0008] The operational amplifier circuit, as the core module of the reference voltage source circuit, ensures the output capacity of the overall circuit, amplifies the bandgap reference voltage, and realizes multi-channel high-precision voltage output. Its input stage adopts a differential input structure composed of NPN tubes, the intermediate stage adopts a common collector amplifier structure composed of PNP tubes, and the output stage adopts a common collector structure composed of NPN tubes; the overall circuit structure is designed around current gain and has strong load driving capability. Compensation capacitors are added between the intermediate stage and the input stage to improve the stability of the circuit. Overcurrent and output port protection circuits are added to the input stage to improve the safety of the entire circuit. A laser trimming scheme is designed in each output sampling resistor, which can be corrected according to the actual test results, improving the output accuracy of the overall circuit.

[0009] Preferably, the reference voltage source circuit includes resistors R1 to R17, NPN transistors N1 to N14, PNP transistors P1 to P7 and capacitor C1;

[0010] The first ends of the resistors R1 to R5 are all connected to the power supply VCC, the second end of the resistor R1 is connected to the collector and base of the NPN tube N3; the emitter of the NPN tube N3 is connected to the collector of the NPN tube N1 and the base of N2; the emitter of the NPN tube N1 is grounded GND;

[0011] The second end of the resistor R2 is connected to the emitter of the PNP tube P4, the base and collector of the PNP tube P4 are simultaneously connected to the collector of the NPN tube N4 and the bases of the PNP tubes P5 to P7; the emitter of the NPN tube N4 is connected to the base of the NPN tube N1 and the collector of N2, and the emitter of the NPN tube N2 is grounded to GND through the resistor R6;

[0012] The second end of the resistor R3 is connected to the emitter of the PNP tube P5, and the collector of the PNP tube P5 is connected to the emitter of the PNP tube P1; the collector and base of the PNP tube P1 are simultaneously connected to the base of the PNP tube P2 and the collector of the NPN tube N5; the base of the NPN tube N5 is simultaneously connected to the first end of the capacitor C1, the first end of the resistor R11 and the collector of the NPN tube N8, and the emitter of the NPN tube N5 and the emitter of the NPN tube N6 are connected to the ground GND through the resistor R7;

[0013] The second end of the resistor R4 is connected to the emitter of the PNP tube P6, and the collector of the PNP tube P6 is simultaneously connected to the emitter of the PNP tube P2, the base of P3 and the second end of the capacitor C1; the collector of the PNP tube P2 is connected to the collector of the NPN tube N6, and the base of the NPN tube N6 is simultaneously connected to the first end of the resistor R10 and the collector of the NPN tube N7;

[0014] The second end of the resistor R5 is connected to the emitter of the PNP tube P7, the collector of the PNP tube P7 is connected to the emitter of the PNP tube P3, the base and collector of the NPN tube N11, and the base of the NPN tube N12, and the collector of the PNP tube P3 is grounded GND;

[0015] The emitter of NPN tube N11 is connected to the collector of NPN tube N10, and the emitter of NPN tube N10 is simultaneously connected to the collector of NPN tube N9, the first end of resistor R16, the first end of resistor R17 and the output port Vout1; the emitter of NPN tube N9 is connected to the second end of resistor R10 and the second end of resistor R11; the base of NPN tube N7 is respectively connected to the base of NPN tube N8, the first end of resistor R14 and the first end of R13; the emitter of NPN tube N7 is connected to the first end of resistor R12, and the second end of resistor R12 is connected to the emitter of NPN tube N8 and the first end of resistor R9; the second end of resistor R9 is grounded to GND through resistor R8;

[0016] The collector of NPN tube N12 is connected to the power supply VCC, and the emitter of NPN tube N12 is connected to the base of NPN tube N10 and the second end of resistor R17; the second end of resistor R16 is connected to the collector of NPN tube N13, the first end of resistor R15 and the output port Vout2; the second end of resistor R15 is connected to the base of NPN tube N9, the collector of NPN tube N14, the second end of resistor R14 and the output port Vout3; the second end of resistor R13 is grounded GND; the base and emitter of NPN tube N13 are commonly grounded GND; the base and emitter of NPN tube N14 are commonly grounded GND.

[0017] Preferably, the magnitude of the start-up current in the startup circuit is determined by a resistor R1, and the resistance value of the resistor R1 is 250 kΩ; the magnitude of the bias current in the bias circuit is determined by a resistor R6.

[0018] Preferably, the bias current is transmitted to the proportional current source by the mirror current source composed of PNP tubes P1 and P2, and the proportional current source is composed of PNP tubes P4 to P7 and resistors R2 to R5, and the bias current required by each branch is determined by the corresponding proportional resistor.

[0019] Preferably, the emitter areas of NPN tubes N7 and N8 in the bandgap reference circuit are designed to be 12:1, so that the tube voltage drop of NPN tube N7 is relatively low. After adding resistor R7, a reference current is generated to achieve static balance of the overall circuit.

[0020] Preferably, the resistor R8 is a P-type base resistor with a high temperature coefficient, and when it is in a certain proportion to the metal film resistor R9, the second-order temperature compensation of the bandgap reference voltage is completed.

[0021] Preferably, the resistor R9 is designed as a "convex"-shaped resistor, and resistance correction is performed using a laser after tape-out to eliminate temperature drift failures caused by process errors.

[0022] Preferably, the differential input structure is composed of NPN tubes N5 and N6; the common collector amplification structure is composed of PNP tube P3; and the common collector structure is composed of NPN tube N12.

[0023] Preferably, the capacitor C1 is a compensation capacitor used to connect the intermediate stage and the input stage; the NPN tubes N10, N11 and resistor R17 constitute an overcurrent protection circuit in the circuit; the NPN tubes N13 and N14 are in the form of emitter and base short-circuited, and are protection devices for the output port.

[0024] Preferably, the calculation formulas for the three reference voltages of the output ports Vout1, Vout2 and Vout3 are as follows:

[0025] Vout1=(R13+R14+R15+R16)*V REF / R13;

[0026] Vout2=(R13+R14+R15)*V REF / R13;

[0027] Vout3=(R13+R14)*V REF / R13;

[0028] Where V REF For the bandgap reference voltage, resistors R14 to R16 are all designed as "convex" shaped resistors.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention provides a high-precision, multi-channel output reference voltage source circuit, which is optimized and designed based on the Brokaw bandgap reference source model. The circuit of the present invention includes a startup circuit, a bias circuit, a bandgap reference circuit and an operational amplifier circuit, and the selection device includes a longitudinal NPN tube, a lateral PNP tube, a MOS capacitor, a metal film resistor and a P-type base resistor. The P-type base resistor is a high temperature coefficient resistor, which can introduce a second-order temperature component to complete the second-order curvature correction of the bandgap reference voltage and realize the second-order temperature compensation of the overall circuit output. The metal film resistor is a low temperature coefficient resistor. In the later stage, the metal film resistor is laser trimmed to improve the output accuracy and temperature drift coefficient of the overall circuit, so as to realize the high-precision and low-temperature drift characteristics of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 It is a functional structure diagram of the overall circuit provided by the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are all in very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0034] like Figure 1 As shown, an embodiment of the present invention provides a high-precision multi-output reference voltage source circuit, comprising:

[0035] The startup circuit is composed of a resistor and a transistor with the collector and base short-circuited. It is equivalent to setting a forward-biased diode and resistor between the power supply and the ground. The startup current can be generated at the moment of power-on, thereby starting the entire circuit. After the circuit is powered on, the safe startup of the entire circuit is completed.

[0036] The bias circuit shares some components with the startup circuit, adopts the form of transistor cross-coupling, combines with resistors to generate bias current, and provides the required bias current for each branch through the current mirror; after the circuit is started, it provides the required static current for each internal branch to ensure the normal operation of the overall circuit;

[0037] The bandgap reference circuit, as the core module of the reference voltage source circuit, provides a bandgap reference voltage with excellent temperature drift performance, which directly determines the temperature drift performance of the entire reference voltage circuit; based on the Brokaw bandgap reference source model design, the bases of two transistors of unequal areas are connected, and a resistor is connected in series between the emitters. Since the emitter area of ​​the transistor determines the size of its tube voltage drop, the voltage difference between the tube voltage drops of the two transistors falls on the resistor, which will generate a reference current and flow through the resistor connected in series with it. Therefore, a bandgap reference voltage is generated, which is composed of the tube voltage drop of the transistor and the voltage dropped on the resistor. At the same time, a laser adjustment scheme is designed in the bandgap reference circuit, which can perform post-correction on the temperature coefficient of the output reference voltage;

[0038] The operational amplifier circuit, as the core module of the reference voltage source circuit, ensures the output capacity of the overall circuit, amplifies the bandgap reference voltage, and realizes multi-channel high-precision voltage output. Its input stage adopts a differential input structure composed of NPN tubes, the intermediate stage adopts a common collector amplifier structure composed of PNP tubes, and the output stage adopts a common collector structure composed of NPN tubes; the overall circuit structure is designed around current gain and has strong load driving capability. Compensation capacitors are added between the intermediate stage and the input stage to improve the stability of the circuit. Overcurrent and output port protection circuits are added to the input stage to improve the safety of the entire circuit. A laser trimming scheme is designed in each output sampling resistor, which can be corrected according to the actual test results, improving the output accuracy of the overall circuit.

[0039] like Figure 1 As shown, in one specific implementation of the present invention, the reference voltage source circuit includes resistors R1 to R17, NPN transistors N1 to N14, PNP transistors P1 to P7 and capacitor C1;

[0040] The first ends of the resistors R1 to R5 are all connected to the power supply VCC, the second end of the resistor R1 is connected to the collector and base of the NPN tube N3; the emitter of the NPN tube N3 is connected to the collector of the NPN tube N1 and the base of N2; the emitter of the NPN tube N1 is grounded GND;

[0041] The second end of the resistor R2 is connected to the emitter of the PNP tube P4, the base and collector of the PNP tube P4 are simultaneously connected to the collector of the NPN tube N4 and the bases of the PNP tubes P5 to P7; the emitter of the NPN tube N4 is connected to the base of the NPN tube N1 and the collector of N2, and the emitter of the NPN tube N2 is grounded to GND through the resistor R6;

[0042] The second end of the resistor R3 is connected to the emitter of the PNP tube P5, and the collector of the PNP tube P5 is connected to the emitter of the PNP tube P1; the collector and base of the PNP tube P1 are simultaneously connected to the base of the PNP tube P2 and the collector of the NPN tube N5; the base of the NPN tube N5 is simultaneously connected to the first end of the capacitor C1, the first end of the resistor R11 and the collector of the NPN tube N8, and the emitter of the NPN tube N5 and the emitter of the NPN tube N6 are connected to the ground GND through the resistor R7;

[0043] The second end of the resistor R4 is connected to the emitter of the PNP tube P6, and the collector of the PNP tube P6 is simultaneously connected to the emitter of the PNP tube P2, the base of P3 and the second end of the capacitor C1; the collector of the PNP tube P2 is connected to the collector of the NPN tube N6, and the base of the NPN tube N6 is simultaneously connected to the first end of the resistor R10 and the collector of the NPN tube N7;

[0044] The second end of the resistor R5 is connected to the emitter of the PNP tube P7, the collector of the PNP tube P7 is connected to the emitter of the PNP tube P3, the base and collector of the NPN tube N11, and the base of the NPN tube N12, and the collector of the PNP tube P3 is grounded GND;

[0045] The emitter of NPN tube N11 is connected to the collector of NPN tube N10, and the emitter of NPN tube N10 is simultaneously connected to the collector of NPN tube N9, the first end of resistor R16, the first end of resistor R17 and the output port Vout1; the emitter of NPN tube N9 is connected to the second end of resistor R10 and the second end of resistor R11; the base of NPN tube N7 is respectively connected to the base of NPN tube N8, the first end of resistor R14 and the first end of R13; the emitter of NPN tube N7 is connected to the first end of resistor R12, and the second end of resistor R12 is connected to the emitter of NPN tube N8 and the first end of resistor R9; the second end of resistor R9 is grounded to GND through resistor R8;

[0046] The collector of NPN tube N12 is connected to the power supply VCC, and the emitter of NPN tube N12 is connected to the base of NPN tube N10 and the second end of resistor R17; the second end of resistor R16 is connected to the collector of NPN tube N13, the first end of resistor R15 and the output port Vout2; the second end of resistor R15 is connected to the base of NPN tube N9, the collector of NPN tube N14, the second end of resistor R14 and the output port Vout3; the second end of resistor R13 is grounded GND; the base and emitter of NPN tube N13 are commonly grounded GND; the base and emitter of NPN tube N14 are commonly grounded GND.

[0047] like Figure 1As shown, the startup circuit is composed of resistors R1 and R6 combined with NPN transistors N2 and N3. Between the power supply VCC and the ground GND, the connection form of the N2 and N3 tubes is equivalent to a forward biased diode, and its conduction voltage is equal to a tube voltage drop. Therefore, after the circuit is powered on, the equivalent diode is forward turned on, and the remaining voltage drops on the resistor, generating a turn-on current, thereby realizing the turn-on of the entire circuit. The turn-on current is determined by the resistor R1. In this embodiment, the resistance of R1 is 250kΩ, which limits the turn-on current to the microampere level, and can ensure the safe start of the circuit.

[0048] like Figure 1 As shown, in one specific embodiment of the present invention, transistors N1 and N2 are connected in a cross-coupled manner, and combined with resistor R6 to generate a bias current, the magnitude of which is determined by resistor R6. The bias current is transmitted from the mirror current source to the proportional current source, which is composed of PNP transistors P4, P5, P6, P7 and resistors R2, R3, R4, and R5. The bias current required for each branch is determined by the corresponding proportional resistor.

[0049] like Figure 1 As shown in the figure, the bandgap reference circuit is designed based on the Brokaw bandgap reference source model and consists of NPN transistors N7 and N8 and resistors R10, R11, R12, R8 and R9. Since the emitter area of ​​N7 and N8 is designed to be 12:1, the tube voltage drop of N7 is relatively low. After adding resistor R7, a reference current is generated to achieve the static balance of the overall circuit. At the same time, the current flowing through N7 and N8 is the reference current. After the two reference currents are superimposed, they flow through resistors R8 and R9 to the ground. The voltage generated on resistors R8 and R9 is added to the tube voltage drop of N8 to output the bandgap reference voltage. Resistor R8 uses a P-type base resistor with a high temperature coefficient. When it is in a certain proportion with the metal film resistor R9, the second-order temperature compensation of the bandgap reference voltage can be completed. Resistor R9 is designed as a "convex"-shaped resistor. After the resistor is corrected by laser after tape-out, the temperature drift failure caused by process errors can be eliminated.

[0050] like Figure 1As shown in the figure, in the operational amplifier circuit, NPN transistors N5 and N6 form a differential input stage, and the mirror current source composed of PNP transistors P1 and P2 is used as a buffer for the input stage circuit, which has strong current and voltage amplification capabilities. PNP transistor P3 is used as an intermediate stage, adopts a common collector amplification structure, and has only current amplification capabilities. The output power tube is NPN transistor N12, which adopts a multi-tube parallel design structure to achieve a larger current output. Compensation capacitor C1 connects the intermediate stage and the input stage to improve the stability of the circuit. NPN transistors N10, N11 and resistor R17 form an overcurrent protection circuit in the circuit. When the output current of the circuit exceeds the protection range, when the voltage on R17 drops to the turn-on voltage of N10, N11 and N10 are turned on, and the input current of N12 in the output stage is discharged to the bandgap reference circuit, thereby closing the output stage circuit of the operational amplifier. When the output current is less than the protection current, the output stage circuit is turned on, thereby realizing overcurrent protection of the circuit. N13 and N14 tubes are in the form of short-circuiting the emitter and base, and are protection devices for the output port. The output current of the operational amplifier is determined by the resistor R13 and the bandgap reference voltage, and the three output reference voltages are determined by the ratio of the resistor R14, the resistor R15, the resistor R16 to the resistor R13 and the bandgap reference voltage, that is:

[0051] Vout1=(R13+R14+R15+R16)*V REF / R13;

[0052] Vout2=(R13+R14+R15)*V REF / R13;

[0053] Vout3=(R13+R14)*V REF / R13;

[0054] Where V REF For the bandgap reference voltage, resistors R14, R15 and R16 all adopt a "convex" type resistor design, which is convenient for later laser adjustment to improve the accuracy of the output reference voltage.

[0055] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A high-precision multi-output reference voltage source circuit, characterized in that: include: The startup circuit is composed of a resistor and a transistor with the collector and base short-circuited; after the circuit is powered on, the safe startup of the entire circuit is completed; The bias circuit uses a cross-coupled transistor to generate a bias current in combination with a resistor, and provides the required bias current to each branch through a current mirror. After the circuit is started, it provides the required static current to each internal branch to ensure the normal operation of the entire circuit. The bandgap reference circuit is designed based on the Brokaw bandgap reference source model. The bases of two transistors of unequal areas are connected and a resistor is connected in series between the emitters. As the core module of the reference voltage source circuit, it provides a bandgap reference voltage with good temperature drift performance, which directly determines the temperature drift performance of the entire reference voltage circuit. The operational amplifier circuit has a differential input structure composed of NPN tubes in the input stage, a common collector amplification structure composed of PNP tubes in the middle stage, and a common collector structure composed of NPN tubes in the output stage. As the core module of the reference voltage source circuit, it guarantees the output capacity of the overall circuit, amplifies the bandgap reference voltage, and realizes multi-channel high-precision voltage output. The reference voltage source circuit includes resistors R1 to R17, NPN transistors N1 to N14, PNP transistors P1 to P7 and capacitor C1; The first ends of the resistors R1 to R5 are all connected to the power supply VCC, the second end of the resistor R1 is connected to the collector and base of the NPN tube N3; the emitter of the NPN tube N3 is connected to the collector of the NPN tube N1 and the base of N2; the emitter of the NPN tube N1 is grounded GND; The second end of the resistor R2 is connected to the emitter of the PNP tube P4, the base and collector of the PNP tube P4 are simultaneously connected to the collector of the NPN tube N4 and the bases of the PNP tubes P5 to P7; the emitter of the NPN tube N4 is connected to the base of the NPN tube N1 and the collector of N2, and the emitter of the NPN tube N2 is grounded to GND through the resistor R6; The second end of the resistor R3 is connected to the emitter of the PNP tube P5, and the collector of the PNP tube P5 is connected to the emitter of the PNP tube P1; the collector and base of the PNP tube P1 are simultaneously connected to the base of the PNP tube P2 and the collector of the NPN tube N5; the base of the NPN tube N5 is simultaneously connected to the first end of the capacitor C1, the first end of the resistor R11 and the collector of the NPN tube N8, and the emitter of the NPN tube N5 and the emitter of the NPN tube N6 are connected to the ground GND through the resistor R7; The second end of the resistor R4 is connected to the emitter of the PNP tube P6, and the collector of the PNP tube P6 is simultaneously connected to the emitter of the PNP tube P2, the base of P3 and the second end of the capacitor C1; the collector of the PNP tube P2 is connected to the collector of the NPN tube N6, and the base of the NPN tube N6 is simultaneously connected to the first end of the resistor R10 and the collector of the NPN tube N7; The second end of the resistor R5 is connected to the emitter of the PNP tube P7, the collector of the PNP tube P7 is connected to the emitter of the PNP tube P3, the base and collector of the NPN tube N11, and the base of the NPN tube N12, and the collector of the PNP tube P3 is grounded GND; The emitter of NPN tube N11 is connected to the collector of NPN tube N10, and the emitter of NPN tube N10 is simultaneously connected to the collector of NPN tube N9, the first end of resistor R16, the first end of resistor R17 and the output port Vout1; the emitter of NPN tube N9 is connected to the second end of resistor R10 and the second end of resistor R11; the base of NPN tube N7 is respectively connected to the base of NPN tube N8, the first end of resistor R14 and the first end of R13; the emitter of NPN tube N7 is connected to the first end of resistor R12, and the second end of resistor R12 is connected to the emitter of NPN tube N8 and the first end of resistor R9; the second end of resistor R9 is grounded to GND through resistor R8; The collector of NPN tube N12 is connected to the power supply VCC, and the emitter of NPN tube N12 is connected to the base of NPN tube N10 and the second end of resistor R17; the second end of resistor R16 is connected to the collector of NPN tube N13, the first end of resistor R15 and the output port Vout2; the second end of resistor R15 is connected to the base of NPN tube N9, the collector of NPN tube N14, the second end of resistor R14 and the output port Vout3; the second end of resistor R13 is grounded GND; the base and emitter of NPN tube N13 are commonly grounded GND; the base and emitter of NPN tube N14 are commonly grounded GND.

2. A high-precision multi-output reference voltage source circuit as claimed in claim 1, characterized in that: The magnitude of the start-up current in the startup circuit is determined by the resistor R1, and the resistance value of the resistor R1 is 250 kΩ; the magnitude of the bias current in the bias circuit is determined by the resistor R6.

3. A high-precision multi-output reference voltage source circuit as claimed in claim 1, characterized in that: The bias current is transmitted to the proportional current source by the mirror current source composed of PNP tubes P1 and P2. The proportional current source is composed of PNP tubes P4-P7 and resistors R2-R5. The bias current required by each branch is determined by the corresponding proportional resistor.

4. A high-precision multi-output reference voltage source circuit as claimed in claim 1, characterized in that: The emitter areas of NPN tubes N7 and N8 in the bandgap reference circuit are designed to be 12:1, so that the tube voltage drop of NPN tube N7 is relatively low. After adding resistor R7, a reference current is generated to achieve static balance of the overall circuit.

5. A high-precision multi-output reference voltage source circuit as claimed in claim 1, characterized in that: The resistor R8 is a P-type base resistor with a high temperature coefficient, and when it is in a certain ratio with the metal film resistor R9, the second-order temperature compensation of the bandgap reference voltage is completed.

6. A high-precision multi-output reference voltage source circuit as claimed in claim 5, characterized in that: The resistor R9 is designed as a "convex" type resistor, and is corrected by laser after tape-out to eliminate temperature drift failures caused by process errors.

7. A high-precision multi-output reference voltage source circuit as claimed in claim 1, characterized in that: The differential input structure is composed of NPN tubes N5 and N6; the common collector amplification structure is composed of PNP tube P3; and the common collector structure is composed of NPN tube N12.

8. A high-precision multi-output reference voltage source circuit as claimed in claim 1, characterized in that: The capacitor C1 is a compensation capacitor used to connect the intermediate stage and the input stage; the NPN tubes N10, N11 and the resistor R17 form an overcurrent protection circuit in the circuit; the NPN tubes N13 and N14 are in the form of short-circuiting the emitter and the base, and are protection devices for the output port.

9. A high-precision multi-output reference voltage source circuit as claimed in any one of claims 1 to 8, characterized in that: The calculation formulas for the three reference voltages of the output ports Vout1, Vout2 and Vout3 are as follows: Vout1=(R13+R14+R15+R16)*V REF / R13; Vout2=(R13+R14+R15)*V REF / R13; Vout3=(R13+R14)*V REF / R13; Where V REF For the bandgap reference voltage, resistors R14~R16 are all designed as "convex" shaped resistors.

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