A high-precision reference voltage circuit

Abstract

The present invention discloses a high-precision reference voltage circuit, which belongs to the field of analog integrated circuits and includes a startup circuit, a bias circuit, and an amplifier circuit. The startup circuit is responsible for the startup work of the circuit after power-on, and at the same time limits the startup branch current of the circuit to within a range, playing a protective role; the bias circuit adopts a cross-coupling structure and combines with a current mirror to complete the output of the reference current; the amplifier circuit is composed of an input stage circuit, an intermediate stage circuit, an output stage circuit, and a common-mode feedback circuit. The input stage circuit adopts a differential input structure, the intermediate stage circuit adopts a common-collector amplification structure, and the output stage circuit adopts a Darlington output structure. The input stage circuit and the output stage circuit are combined with a common-mode feedback circuit to achieve stable signal output. The present invention selects metal film resistors with good temperature characteristics to complete the sampling of the reference voltage, thereby ensuring the temperature characteristics of the reference voltage; the metal film thin resistors in the later stage are subjected to high-precision laser trimming to ensure the high-precision output of the reference voltage.

Description

Technical Field

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

[0002] With the continuous advancement of semiconductor technology, integrated circuits have evolved from analog to digital circuits. To achieve both analog and digital performance, hybrid analog circuits have emerged. As the core module of these circuits, the reference voltage circuit plays a crucial role. The reference voltage's parameters directly determine the overall performance of the circuit. However, integrated reference voltage circuits often exhibit unsatisfactory performance due to their power consumption and area requirements, requiring designers to expend considerable effort to adjust and match the overall circuit. Summary of the Invention

[0003] The object of the present invention is to provide a high-precision reference voltage circuit to solve the problems in the background technology.

[0004] To solve the above technical problems, the present invention provides a high-precision reference voltage circuit, comprising:

[0005] The starting circuit is responsible for starting the circuit after power is turned on, and at the same time limits the starting branch current of the circuit within a certain range to play a protective role;

[0006] The bias circuit adopts a cross-coupling structure and combines with a current mirror to complete the output of the reference current;

[0007] The amplifier circuit is composed of an input stage circuit, an intermediate stage circuit, an output stage circuit and a common-mode feedback circuit. The input stage circuit adopts a differential input structure, the intermediate stage circuit adopts a common-collector amplification structure, and the output stage circuit adopts a Darlington output structure. The input stage circuit and the output stage circuit are combined with the common-mode feedback circuit to achieve stable signal output.

[0008] In one embodiment, the high-precision reference voltage circuit includes resistors R1 to R 17 、NPN tube N1~N 18 , PNP tubes P1~P7 and capacitor C1;

[0009] The first ends of resistors R1 to R6 are connected to the power supply V CC The second end of the resistor R1 is connected to the collector and base of the NPN tube N1; the emitter of the NPN tube N1 is connected to the collector of the NPN tube N3 and the base of the NPN tube N4; the emitter of the NPN tube N3 is grounded;

[0010] The second end of resistor R2 is connected to the emitter of PNP tube P1, the base and collector of PNP tube P1 are connected to the first end of resistor R7, the second end of resistor R7 is connected to the collector of NPN tube N2; the base of NPN tube N2 is connected to the base of NPN tube N1, and the emitter is connected to NPN tube N 18 The base of the NPN tube and the collector of the NPN tube N4; the collector of the NPN tube N4 is connected to the base of the NPN tube N3, and the emitter is grounded through the resistor R8;

[0011] The second end of the resistor R3 is connected to the emitter of the PNP tube P2, and the collector of the PNP tube P2 is connected to the base of the PNP tube P4 and the NPN tube N 18 The collector of the NPN tube N8 is connected to the collector of the NPN tube N8; the emitter of the NPN tube N 10 The collector;

[0012] The second end of resistor R4 is connected to the emitter of PNP tube P3, the base of PNP tube P3 is connected to its own collector and the base of PNP tube P2, the collector of PNP tube P3 is connected to the emitter of PNP tube P4; the collector of PNP tube P4 is connected to the collector of NPN tube N9, and the emitter of NPN tube N 11 The collector of NPN tube N 11 The emitter and NPN tube N 10 The emitters are connected to NPN tube N 12 The collector of NPN tube N 12 The emitter of the 15 grounding;

[0013] The second end of the resistor R5 is connected to the emitter of the PNP tube P5 and the NPN tube N 13 The collector of the PNP tube P5 is connected to the base of the PNP tube P1, and the collector is also connected to the NPN tube N 14 The collector and NPN tube N 16 The base of NPN tube N 14 The base is connected to its own collector, and the emitter is connected to the NPN tube N 15 Collector of NPN tube N 15 The base of is connected to its own collector, and the emitter is connected to the emitter of PNP tube P6; the base of PNP tube P6 is connected to the collector of NPN tube N9, and the collector is grounded;

[0014] The second end of resistor R6 is connected to the NPN transistor N 13 The emitter of NPN tube N 16 The collector and NPN tube N 17 Collector of NPN tube N 13 The base is connected to the power supply V CC;NPN tube N 16 The base is connected to the collector of the PNP tube P5, and the emitter is connected to the NPN tube N 17 The base of NPN tube N 17 The emitter of is connected to the collector of NPN tube N5 and resistor R 16 The first end of the resistor R 16 The second end is connected through the resistor R 17 grounding;

[0015] The base of NPN tube N5 is connected to its own collector, and the emitter is connected to the first end of resistor R9 and the resistor R 10 The first end of the resistor R9 is connected to the base of the NPN tube N8 and the base of the NPN tube N9; the second end of the resistor R9 is connected to the collector of the NPN tube N6, the second end of the capacitor C1 and the NPN tube N 11 The first end of capacitor C1 is connected to the base of PNP tube P6; resistor R 10 The second end is connected to the NPN tube N 10 The base of NPN tube N6 is connected to the collector of NPN tube N7 through resistor R 12 At the same time, connect the base of NPN tube N7 and NPN tube N 12 The base of NPN tube N6 is connected to the emitter of resistor R 11 The first end of the resistor R 11 The second end is connected to the NPN tube N 18 The emitter, resistor R 13 The first end and the emitter of NPN tube N7, resistor R 13 The second end of the resistor R 14 The first end and the emitter of PNP tube P7, resistor R 14 The second end of the PNP tube P7 is grounded; the base and collector of the PNP tube P7 are both grounded.

[0016] In one embodiment, the resistor R 17 Select metal film resistors with ultra-low temperature drift to ensure the temperature stability of the output reference voltage; the resistor R 17 It has a convex shape and is later trimmed by laser to perform high-precision resistance correction based on the deviation of the wafer process to ensure high-precision output reference voltage.

[0017] In one embodiment, the resistor R1 is a starting resistor with a resistance of 200k ohms.

[0018] In one embodiment, the resistor R8 is a resistor for generating bias current and is set according to actual needs.

[0019] In one embodiment, the NPN transistor N1 is designed as a multi-tube parallel connection, so that the tube voltage drop of the NPN transistor N1 is smaller than the tube voltage drop of the NPN transistor N2, and the emitter potential of the NPN transistor N1 is higher than the emitter potential of the NPN transistor N2, and the voltage difference is ΔV be .

[0020] In one embodiment, the NPN transistor N3 and the NPN transistor N4 are a cross-current mirror, and the emitter potential of the NPN transistor N4 is higher than the emitter potential of the NPN transistor N3 by ΔV. be .

[0021] In one embodiment, the NPN transistor N 14 、The NPN tube N 15 The voltage clamping is achieved by shorting the base and collector.

[0022] In one embodiment, the base and collector of the PNP transistor P7 are short-circuited to serve as a clamping diode to limit the bias current of the common-mode feedback circuit.

[0023] The present invention provides a high-precision reference voltage circuit, comprising a startup circuit, a bias circuit, and an amplifier circuit. This circuit selects metal film resistors with good temperature characteristics to sample the reference voltage, ensuring the reference voltage's temperature characteristics. Furthermore, high-precision laser trimming is performed on the metal film resistors to ensure high-precision output of the reference voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a high-precision reference voltage circuit proposed by the present invention;

[0025] Figure 2 This is a diagram of laser trimming of thin film resistors. DETAILED DESCRIPTION

[0026] The following is a detailed description of a high-precision voltage reference circuit according to the present invention, with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are greatly simplified and not to exact scale, and are intended solely to facilitate and clearly illustrate the embodiments of the present invention.

[0027] The present invention provides a high-precision reference voltage circuit, which can provide a high-precision and high-stability reference voltage by laser trimming of metal film resistors in the later stage. The overall high-precision reference voltage circuit mainly includes a startup circuit, a bias circuit and an amplifier circuit.

[0028] The startup circuit consists of a startup resistor, a transistor with its collector and base shorted, and the base-emitter and resistor of the transistor in the bias circuit. When the circuit is powered on, the transistor and resistor form a conductive path, and the startup resistor limits the current in this path, protecting the circuit.

[0029] The core of the bias circuit consists of a cross-coupled current mirror and resistors. The difference in the number of transistors connected in parallel between the current mirrors results in different voltage drops across the two transistors. When the circuit is powered on, a voltage difference between the emitters of the two transistors relative to ground is generated. This voltage difference is applied to the resistors, generating a bias current that is then transferred to each module through the current mirror.

[0030] The amplifier circuit adopts a conventional three-stage amplification structure, providing a stable current output, which is then sampled by a resistor to output a stable reference voltage. The amplifier circuit includes an input stage circuit, an intermediate stage circuit, an output stage circuit, and a common-mode feedback circuit. The input stage circuit adopts a differential input structure, which improves input stage gain while reducing input stage offset. The intermediate stage adopts a voltage follower structure, amplifying current while increasing its buffering capacity. The output stage circuit adopts a Darlington output structure, which greatly improves the output stage's current amplification capability and makes the amplifier's closed-loop output gain more precise. The input and output stage circuits, combined with the common-mode feedback circuit, achieve stable signal output.

[0031] like Figure 1 As shown in FIG, the present invention provides a structural diagram of a high-precision reference voltage circuit, including resistors R1 to R 17 、NPN tube N1~N 18 , PNP tubes P1~P7 and capacitor C1;

[0032] The first ends of resistors R1 to R6 are connected to the power supply V CC The second end of the resistor R1 is connected to the collector and base of the NPN tube N1; the emitter of the NPN tube N1 is connected to the collector of the NPN tube N3 and the base of the NPN tube N4; the emitter of the NPN tube N3 is grounded;

[0033] The second end of resistor R2 is connected to the emitter of PNP tube P1, the base and collector of PNP tube P1 are connected to the first end of resistor R7, the second end of resistor R7 is connected to the collector of NPN tube N2; the base of NPN tube N2 is connected to the base of NPN tube N1, and the emitter is connected to NPN tube N 18 The base of the NPN tube and the collector of the NPN tube N4; the collector of the NPN tube N4 is connected to the base of the NPN tube N3, and the emitter is grounded through the resistor R8;

[0034] The second end of the resistor R3 is connected to the emitter of the PNP tube P2, and the collector of the PNP tube P2 is connected to the base of the PNP tube P4 and the NPN tube N 18 The collector of the NPN tube N8 is connected to the collector of the NPN tube N8; the emitter of the NPN tube N 10 The collector;

[0035] The second end of resistor R4 is connected to the emitter of PNP tube P3, the base of PNP tube P3 is connected to its own collector and the base of PNP tube P2, the collector of PNP tube P3 is connected to the emitter of PNP tube P4; the collector of PNP tube P4 is connected to the collector of NPN tube N9, and the emitter of NPN tube N 11 The collector of NPN tube N 11 The emitter and NPN tube N 10 The emitters are connected to NPN tube N 12 The collector of NPN tube N 12 The emitter of the 15 grounding;

[0036] The second end of the resistor R5 is connected to the emitter of the PNP tube P5 and the NPN tube N 13 The collector of the PNP tube P5 is connected to the base of the PNP tube P1, and the collector is also connected to the NPN tube N 14 The collector and NPN tube N 16 The base of NPN tube N 14 The base is connected to its own collector, and the emitter is connected to the NPN tube N 15 Collector of NPN tube N 15 The base of is connected to its own collector, and the emitter is connected to the emitter of PNP tube P6; the base of PNP tube P6 is connected to the collector of NPN tube N9, and the collector is grounded;

[0037] The second end of resistor R6 is connected to the NPN transistor N 13 The emitter of NPN tube N 16 The collector and NPN tube N 17 Collector of NPN tube N 13 The base is connected to the power supply V CC ;NPN tube N 16 The base is connected to the collector of the PNP tube P5, and the emitter is connected to the NPN tube N 17 The base of NPN tube N 17 The emitter of is connected to the collector of NPN tube N5 and resistor R 16 The first end of the resistor R 16 The second end is connected through the resistor R 17 grounding;

[0038] The base of NPN tube N5 is connected to its own collector, and the emitter is connected to the first end of resistor R9 and the resistor R 10 The first end of the resistor R9 is connected to the base of the NPN tube N8 and the base of the NPN tube N9; the second end of the resistor R9 is connected to the collector of the NPN tube N6, the second end of the capacitor C1 and the NPN tube N 11 The first end of capacitor C1 is connected to the base of PNP tube P6; resistor R 10 The second end is connected to the NPN tube N 10 The base of NPN tube N6 is connected to the collector of NPN tube N7 through resistor R 12 At the same time, connect the base of NPN tube N7 and NPN tube N 12 The base of NPN tube N6 is connected to the emitter of resistor R 11 The first end of the resistor R 11 The second end is connected to the NPN tube N 18 The emitter, resistor R 13 The first end and the emitter of NPN tube N7, resistor R 13 The second end of the resistor R 14 The first end and the emitter of PNP tube P7, resistor R 14 The second end of the PNP tube P7 is grounded; the base and collector of the PNP tube P7 are both grounded.

[0039] Resistors R1, R8, NPN transistors N1, and NPN transistors N4 form the startup circuit, forming a conductive path when the circuit is powered on. Resistor R1 is the startup resistor, and its high resistance significantly reduces the startup current, protecting the entire circuit from damage. During power-up, NPN transistors N1 and NPN transistors N4 each consume a voltage drop, with the remaining voltage dropped across resistors R1 and R8. Since resistor R8 acts as a bias current generator and needs to be set according to actual needs, the size of resistor R1 directly determines the startup current.

[0040] Resistors R2, R7, R8, NPN transistors N2, NPN transistors N3, NPN transistors N4, and PNP transistor P1 form a bias circuit. After the circuit is powered on, the current mirror formed by NPN transistors N1 and NPN transistors N2 begins to operate normally. Since NPN transistor N1 is a multi-tube parallel design, the tube voltage drop of NPN transistor N1 is smaller than the tube voltage drop of NPN transistor N2. The emitter potential of NPN transistor N1 is higher than the emitter potential of NPN transistor N2, and the voltage difference between them is △V be Since NPN tubes N3 and NPN tubes N4 form a cross-current mirror, the emitter potential of NPN tube N4 is higher than that of NPN tube N3 by △V. be , that is, the voltage dropped on resistor R8, so the bias current of the entire circuit is determined by the size of resistor R8.

[0041] The amplifier circuit includes an input stage circuit, an intermediate stage circuit, an output stage circuit and a common mode feedback circuit. 10 、NPN tube N 11 It is the input differential pair of the amplifier circuit, and its common-mode input voltage is provided by the common-mode feedback circuit; NPN tube N8 and NPN tube N9 form the buffer structure of the input stage to enhance the stability of the input stage circuit; NPN tube N 12 With resistor R 15 Provides bias current for the input stage, the size of which is determined by the output stage circuit. The Wilson current source composed of PNP tube P2, PNP tube P3, PNP tube P4, resistor R3, and resistor R4 serves as the load of the input stage circuit, greatly improving the amplification capability of the input stage circuit; the compensation capacitor C1 connecting the intermediate stage circuit and the input stage circuit ensures the stability of the circuit. PNP tube P6 serves as the amplifier tube of the intermediate stage circuit. In order to improve the stability of the circuit, it adopts a voltage follower structure to achieve the ability of current amplification and voltage following. Its bias current is provided by PNP tube P1, PNP tube P5, resistor R5, and NPN tube N 14 、NPN tube N 15 The voltage clamping is achieved by shorting the base and collector. 16 、NPN tube N 17 The Darlington structure is the guarantee of the output stage current amplification capability. The resistor R6 is the sampling resistor of the output stage circuit. When the output current exceeds the protection range, the voltage dropped on the resistor R6 will 13 When turned on, it can limit the output current of the intermediate stage, thereby reducing the input current of the output stage and achieving circuit protection. 16 , resistor R 17 It is the sampling resistor of the output stage circuit. When the output current stabilizes, it falls on the resistor R 16 , resistor R 17 The voltage on the resistor R is stable, that is, the entire circuit outputs a stable reference voltage. 17 Designed as a convex shape, it can be laser trimmed with high precision in the later stage to ensure the microvolt output accuracy of the reference voltage. 18 , PNP tube P7 combined with resistor R9, resistor R 10 , resistor R 11 , resistor R 12 , resistor R 13 , resistor R 14This forms a common-mode feedback circuit, providing a stable, symmetrical common-mode input level and input bias current for the input differential pair transistors. The base-collector terminals of PNP transistor P7 are shorted together to act as a clamping diode, limiting the bias current in the common-mode feedback circuit and improving circuit stability.

[0042] like Figure 2 The figure below shows a laser trimming diagram of a metal film resistor. R1 is a convex resistor with the thinner parts at both ends being the resistor tips and the protruding part in the middle being the resistor body. Due to deviations in the production process, the resistance value of the resistor differs from the theoretical value, which will affect the accuracy of the output reference voltage. High-precision laser trimming is required after the tape-out is completed. This resistor is designed using a metal film resistor and is mainly composed of chromium and silicon. During laser cutting, the chromium component in the resistor will evaporate through the passivation layer, thereby irreversibly changing the resistance value of the resistor. R2 is the resistor graphic after laser trimming. The horizontal blank space in the protruding part indicates the laser trimming part. Not only that, the entire resistor body can be laser trimmed. The change in resistance varies depending on the trimming position, and ohm-level trimming can be achieved. Therefore, when performing high-precision laser trimming on the circuit, it needs to be performed under test conditions.

[0043] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians 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 reference voltage circuit, characterized in that: include: The starting circuit is responsible for starting the circuit after power is turned on, and at the same time limits the starting branch current of the circuit within a certain range to play a protective role; The bias circuit adopts a cross-coupling structure and combines with a current mirror to complete the output of the reference current; An amplifier circuit, comprising an input stage circuit, an intermediate stage circuit, an output stage circuit, and a common-mode feedback circuit. The input stage circuit adopts a differential input structure, the intermediate stage circuit adopts a common-collector amplifier structure, and the output stage circuit adopts a Darlington output structure. The input stage circuit and the output stage circuit, combined with the common-mode feedback circuit, achieve stable signal output. The high-precision reference voltage circuit includes resistors R1 to R 17 、NPN tube N1~N 18 , PNP tubes P1~P7 and capacitor C1; The first ends of resistors R1 to R6 are connected to the power supply V CC The second end of the resistor R1 is connected to the collector and base of the NPN tube N1; the emitter of the NPN tube N1 is connected to the collector of the NPN tube N3 and the base of the NPN tube N4; the emitter of the NPN tube N3 is grounded; The second end of resistor R2 is connected to the emitter of PNP tube P1, the base and collector of PNP tube P1 are connected to the first end of resistor R7, the second end of resistor R7 is connected to the collector of NPN tube N2; the base of NPN tube N2 is connected to the base of NPN tube N1, and the emitter is connected to NPN tube N 18 The base of the NPN tube and the collector of the NPN tube N4; the collector of the NPN tube N4 is connected to the base of the NPN tube N3, and the emitter is grounded through the resistor R8; The second end of the resistor R3 is connected to the emitter of the PNP tube P2, and the collector of the PNP tube P2 is connected to the base of the PNP tube P4 and the NPN tube N 18 The collector of the NPN tube N8 is connected to the collector of the NPN tube N8; the emitter of the NPN tube N 10 The collector; The second end of resistor R4 is connected to the emitter of PNP tube P3, the base of PNP tube P3 is connected to its own collector and the base of PNP tube P2, the collector of PNP tube P3 is connected to the emitter of PNP tube P4; the collector of PNP tube P4 is connected to the collector of NPN tube N9, and the emitter of NPN tube N 11 The collector of NPN tube N 11 The emitter and NPN tube N 10 The emitters are connected to NPN tube N 12 The collector of NPN tube N 12 The emitter of the 15 grounding; The second end of the resistor R5 is connected to the emitter of the PNP tube P5 and the NPN tube N 13 The collector of the PNP tube P5 is connected to the base of the PNP tube P1, and the collector is also connected to the NPN tube N 14 The collector and NPN tube N 16 The base of NPN tube N 14 The base is connected to its own collector, and the emitter is connected to the NPN tube N 15 Collector of NPN tube N 15 The base of is connected to its own collector, and the emitter is connected to the emitter of PNP tube P6; the base of PNP tube P6 is connected to the collector of NPN tube N9, and the collector is grounded; The second end of resistor R6 is connected to the NPN transistor N 13 The emitter of NPN tube N 16 The collector and NPN tube N 17 Collector of NPN tube N 13 The base is connected to the power supply V CC ;NPN tube N 16 The base is connected to the collector of the PNP tube P5, and the emitter is connected to the NPN tube N 17 The base of NPN tube N 17 The emitter of is connected to the collector of NPN tube N5 and resistor R 16 The first end of the resistor R 16 The second end is connected through the resistor R 17 grounding; The base of NPN tube N5 is connected to its own collector, and the emitter is connected to the first end of resistor R9 and the resistor R 10 The first end of the resistor R9 is connected to the base of the NPN tube N8 and the base of the NPN tube N9; the second end of the resistor R9 is connected to the collector of the NPN tube N6, the second end of the capacitor C1 and the NPN tube N 11 The first end of capacitor C1 is connected to the base of PNP tube P6; resistor R 10 The second end is connected to the NPN tube N 10 The base of NPN tube N6 is connected to the collector of NPN tube N7 through resistor R 12 At the same time, connect the base of NPN tube N7 and NPN tube N 12 The base of NPN tube N6 is connected to the emitter of resistor R 11 The first end of the resistor R 11 The second end is connected to the NPN tube N 18 The emitter, resistor R 13 The first end and the emitter of NPN tube N7, resistor R 13 The second end of the resistor R 14 The first end and the emitter of PNP tube P7, resistor R 14 The second end of the PNP tube P7 is grounded; the base and collector are both grounded; The resistor R 17 Select metal film resistors with ultra-low temperature drift to ensure the temperature stability of the output reference voltage; the resistor R 17 It has a convex shape and is later trimmed by laser to perform high-precision resistance correction based on the deviation of the wafer process to ensure high-precision output reference voltage.

2. The high-precision reference voltage circuit according to claim 1, wherein: The resistor R1 is a starting resistor with a resistance of 200k ohms.

3. The high-precision reference voltage circuit according to claim 1, wherein: The resistor R8 is a resistor for generating bias current and is set according to actual needs.

4. The high-precision reference voltage circuit according to claim 1, wherein: The NPN tube N1 is designed as a multi-tube parallel connection, so that the tube voltage drop of the NPN tube N1 is smaller than the tube voltage drop of the NPN tube N2. The emitter potential of the NPN tube N1 is higher than the emitter potential of the NPN tube N2, and the voltage difference is △V be .

5. The high-precision reference voltage circuit according to claim 1, wherein: The NPN tube N3 and the NPN tube N4 form a current mirror formed by crossing each other. The emitter potential of the NPN tube N4 is higher than the emitter potential of the NPN tube N3 by ΔV. be .

6. The high-precision reference voltage circuit according to claim 1, wherein: The NPN tube N 14 、The NPN tube N 15 The voltage clamping is achieved by shorting the base and collector.

7. The high-precision reference voltage circuit according to claim 1, wherein: The base and collector of the PNP transistor P7 are short-circuited to serve as a clamping diode to limit the bias current of the common-mode feedback circuit.

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