Bandgap reference voltage generator

Abstract

To provide a bandgap-type reference-voltage generating circuit capable of outputting a stable reference voltage with the effect of base resistance lowered.SOLUTION: A bandgap-type reference-voltage generating circuit comprises: a first node connected to an output end; a second node connected to a first current source; a third node connected to a second current source; a fourth node; a first bipolar junction transistor having a base connected to the first node; a second bipolar junction transistor having a base connected to the first node; a third bipolar junction transistor connected at an emitter-collector path between the second node and the fourth node so as to amplify the output current of the first bipolar junction transistor; and a fourth bipolar junction transistor connected at an emitter-collector path between the third node and the fourth node so as to amplify the output current of the second bipolar junction transistor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This embodiment relates to a bandgap reference voltage generating circuit. [Background technology]

[0002] Conventionally, a bandgap reference voltage generating circuit that utilizes the bandgap voltage (the inherent voltage of a semiconductor, approximately 1.2 V in the case of silicon) is known. A conventional bandgap reference voltage generating circuit will be explained with reference to FIG.

[0003] The bandgap reference voltage generating circuit shown in Fig. 6 has NPN bipolar junction transistors 50 and 60, which form a Brokaw cell, and resistors R3 and R4. Hereinafter, the bipolar junction transistor may be referred to as BJT. The emitter of the NPN BJT 50 is connected to the connection point N01 of the resistors R3 and R4.

[0004] A constant current source 30 is connected to the collector of the NPN BJT 50. The constant current source 30 supplies a current I1. A constant current source 40 is connected to the collector of the NPN BJT 60. The constant current source 40 supplies a current I2. The currents I1 and I2 are set to the same value. A resistor R4 is connected to a reference voltage V REF This resistor adjusts the temperature coefficient of the reference voltage V by setting the resistance ratio with resistor R3. REF Adjust the temperature coefficient.

[0005] The emitter area ratio of NPN BJT 50 and NPN BJT 60 is set to 1:N, where N is any positive number greater than 1. Resistor RB1 indicates the base resistance of NPN BJT 50. Resistor RB2 indicates the base resistance of NPN BJT 60. According to the emitter area ratio N of NPN BJTs 50 and 60, the ratio of the resistance values ​​of resistors RB1 and RB2 is 1:(1 / N). In other words, if the base resistance of NPN BJT 50 is RB, the base resistance of NPN BJT 60 is RB / N. The difference voltage ΔV between the base-emitter voltages of NPN BJTs 50 and 60 is applied across resistor R3. BE The difference voltage ΔVBE is expressed as (kT / q)·lnN, where k is the Boltzmann coefficient, T is the absolute temperature, q is the electron charge, and N is the ratio of the emitter areas of NPN-type BJTs 50 and 60.

[0006] Set the currents I1 and I2 to the same value, that is, set the collector currents of NPN BJTs 50 and 60 to the same value I C When set to , the base-emitter voltage V of the NPN BJT50 BE1real and the base-emitter voltage V of the NPN BJT60 BE2real is shown in equation (1) and equation (2).

[0007]

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[0008] Voltage drop V across resistor R4 R4real is generated by the sum of the collector currents and emitter currents flowing through NPN BJTs 50 and 60, and is expressed by equation (3).

[0009]

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[0010] The reference voltage V of node N00, where the bases of NPN BJT50 and NPN BJT60 are commonly connected REF is expressed by the formula (4). Note that the configuration for supplying a base current to the node N00 is omitted.

[0011]

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[0012] As shown in equation (4), the reference voltage V REF It can be seen that there is a voltage component due to the base resistance RB in

[0013] The temperature coefficient of the base resistance RB is positive in the case of a Si semiconductor. Therefore, the reference voltage V REF contains a voltage component with a positive temperature coefficient. Also, due to the variation in the base resistance RB, the reference voltage V REF The inventors have determined that the value of the reference voltage V REF We propose a bandgap reference voltage generator that can reduce the effect of the base resistance RB by focusing on the characteristics of the base resistance RB. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Patent No. 6136480 Summary of the Invention [Problem to be solved by the invention]

[0015] An object of one embodiment is to provide a bandgap reference voltage generating circuit capable of outputting a stable reference voltage by reducing the influence of base resistance. [Means for solving the problem]

[0016] According to one embodiment, a bandgap type reference voltage generating circuit includes a first node connected to an output terminal, a second node connected to a first current source, a third node connected to a second current source, a fourth node, a first bipolar junction transistor having a base connected to the first node, a second bipolar junction transistor having a base connected to the first node, a third bipolar junction transistor having an emitter-collector path connected between the second node and the fourth node and amplifying an output current of the first bipolar junction transistor, and a fourth bipolar junction transistor having an emitter-collector path connected between the third node and the fourth node and amplifying an output current of the second bipolar junction transistor. a first resistor constituting the first current source, a second resistor constituting the second current source, a third resistor having one end connected to the emitter of the second bipolar junction transistor and the other end connected to the base of a fourth bipolar junction transistor, and a fourth resistor having one end connected to the fourth node and the other end grounded; Equipped with: [Brief description of the drawings]

[0017] [Figure 1] 1 is a diagram showing a configuration of a bandgap reference voltage generating circuit according to a first embodiment. [Diagram 2] 4A to 4C are diagrams for explaining the effects of the bandgap reference voltage generating circuit according to the first embodiment; [Diagram 3] FIG. 13 is a diagram showing a configuration of a bandgap reference voltage generating circuit according to a second embodiment. [Figure 4] FIG. 13 is a diagram showing a configuration of a bandgap reference voltage generating circuit according to a third embodiment. [Diagram 5] FIG. 13 is a diagram showing a configuration of a bandgap reference voltage generating circuit according to a fourth embodiment. [Figure 6] FIG. 1 is a diagram showing a configuration of a conventional bandgap reference voltage generating circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, a bandgap reference voltage generating circuit according to an embodiment will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments.

[0019] (First embodiment) 1 is a diagram showing the configuration of a bandgap reference voltage generating circuit according to a first embodiment. This embodiment has nodes N1 to N4. Node N1 is connected to an output terminal 3. Node N2 is connected to a power supply voltage V DD A voltage is applied to the node N3, which is connected to the power supply line 1. The node N3 is connected to the power supply line 1 via a resistor R2. The resistors R1 and R2 form a current source.

[0020] This embodiment has a Darlington pair 10A. The Darlington pair 10A has an NPN BJT 11 whose base is connected to a node N1, and an NPN BJT 12. The collectors of the NPN BJTs 11 and 12 are connected to a node N2. The emitter-collector path of the NPN BJT 12 is connected between the nodes N2 and N4. The base of the NPN BJT 12 is connected to the emitter of the NPN BJT 11, and the NPN BJT 12 amplifies the output current of the NPN BJT 11. The base resistor of the NPN BJT 12 is omitted for convenience.

[0021] This embodiment has a Darlington pair 10B. The Darlington pair 10B has an NPN BJT 21 whose base is connected to a node N1, and an NPN BJT 22. The collectors of the NPN BJTs 21 and 22 are connected to a node N3. The emitter of the NPN BJT 21 is connected to a node N4 via a resistor R3. The emitter-collector path of the NPN BJT 22 is connected between the nodes N3 and N4. The base of the NPN BJT 22 is connected to the emitter of the NPN BJT 21, and the NPN BJT 22 amplifies the output current of the NPN BJT 21. The base resistor of the NPN BJT 22 is omitted for convenience.

[0022] This embodiment has a resistor R1 connected between node N2 and the power supply line 1. The resistor R1 is connected between the Darlington pair 10A and the power supply line 1 and constitutes a current source. Similarly, the resistor R2 is connected between the Darlington pair 10B and the power supply line 1 and constitutes a current source. The resistance values ​​of the resistors R1 and R2 are set to the same value.

[0023] This embodiment has a differential amplifier circuit 2 that supplies an output signal to a node N1 according to the difference in voltage drops occurring across resistors R1 and R2 that constitute a current source. The voltage of node N2 is supplied to the inverting input terminal (-) of the differential amplifier circuit 2, and the voltage of node N3 is supplied to the non-inverting input terminal (+).

[0024] The differential amplifier circuit 2 compares the voltages of the nodes N2 and N3, and controls the voltage of the node N1 so that the voltage drops across the resistors R1 and R2 become equal. Therefore, when the resistance values ​​of the resistors R1 and R2 are set to the same value, the currents I1 and I2 supplied to the Darlington pairs 10A and 10B are controlled to be the same.

[0025] The node N1 is connected to the output terminal 3. The output terminal 3 is connected to a reference voltage V REF Output.

[0026] In the bandgap reference voltage generating circuit of this embodiment, the cells constituting the Brokowa cell include Darlington pairs 10A and 10B. That is, NPN BJTs 12 and 22 are provided which respectively amplify the output currents of NPN BJTs 11 and 21 whose bases are connected to node N1. Therefore, if the current gains of the NPN BJTs 11 and 21 are β1 and the current gains of the NPN BJTs 12 and 22 are β2, then the current gain β of the Darlington pairs 10A and 10B is β1·β2+β1+β2.

[0027] Therefore, the reference voltage V REF can be expressed by substituting the current gain β1·β2+β1+β2 instead of β in the above-mentioned equation (4). In other words, by using a configuration including the Darlington pair 10A and 10B, the denominator value in the second term in equation (4) can be increased, thereby reducing the effect of the base resistance RB. As a result, the reference voltage V REF This suppresses the change in the temperature coefficient of the reference voltage V due to the variation in the resistance value of the base resistor RB. REF It is possible to suppress the variation in the

[0028] 2 is a diagram for explaining the effect of the first embodiment, showing a comparison result with a conventional bandgap reference voltage generating circuit.

[0029] The upper part of FIG. 2 shows the reference voltage V REF The vertical axis indicates the temperature, and the horizontal axis indicates the temperature. The graph shows the simulation results when the temperature was changed from -50°C to 190°C. The solid line 100 indicates the simulation results when the base resistance RB was set to 130Ω, and the solid line 101 indicates the simulation results when the base resistance RB was set to 330Ω.

[0030] The lower row shows the reference voltage V of the bandgap reference voltage generator of the conventional configuration shown in Fig. 6. REF 2 shows the results of a simulation in the case where the temperature is changed from −50° C. to 190° C. A solid line 200 shows the results of a simulation in the case where the base resistance RB is set to 130 Ω, and a solid line 201 shows the results of a simulation in the case where the base resistance RB is set to 330 Ω.

[0031] In the simulation, the chip area of ​​NPN BJTs 21 and 22 of Darlington pair 10B was set to four times the chip area of ​​NPN BJTs 11 and 12 of Darlington pair 10A, and in the conventional configuration, the chip area of ​​NPN BJT 60 was set to eight times the chip area of ​​NPN BJT 50. That is, the area ratio of the entire elements was set to 10 (=2×4+2×1) in this embodiment and 9 (=8+1) in the conventional configuration, and the bandgap reference voltage generating circuits were configured with approximately the same chip area to perform the simulation.

[0032] It can be seen that the temperature characteristics of this embodiment are improved compared to the bandgap reference voltage generating circuit of the conventional configuration shown in the lower part. The effect of the improvement is particularly noticeable when the base resistance RB is high. REF The first-order approximation of the temperature coefficient of the reference voltage V at 27°C REFIn the conventional configuration, the value obtained by dividing the resistance by the base resistance RB is −0.05 ppm / ° C. in a simulation in which the base resistance RB is set to 130 Ω, and is 1.33 ppm / ° C. in a simulation in which the base resistance RB is set to 330 Ω, whereas in this embodiment, the value is −0.14 ppm / ° C. in a simulation in which the base resistance RB is set to 130 Ω, and is 0.17 ppm / ° C. in a simulation in which the base resistance RB is set to 330 Ω. According to this embodiment, the influence of the base resistance RB is reduced, so that the reference voltage V REF The temperature characteristics of the base resistor RB are improved to reduce the effect of variations in the base resistor RB, resulting in a stable reference voltage V REF It is possible to provide.

[0033] According to this embodiment, the reference voltage V REF The effect of the base resistance RB in the reference voltage V REF For example, when a bipolar junction transistor is produced by a CMOS process, the current gain tends to be small. According to this embodiment, a bandgap reference voltage generating circuit capable of increasing the current gain can be provided, and therefore, even when there are constraints in the manufacturing process, etc., a bandgap reference voltage generating circuit in which the influence of the base resistance RB is reduced can be provided.

[0034] According to this embodiment, the reference voltage V REF is the sum of the base-emitter voltage of the NPN BJTs 11 and 12 that make up the Darlington pair 10A and the voltage drop across resistor R4. Therefore, for example, when the reference voltage V REF This is suitable for obtaining

[0035] Second Embodiment 3 is a diagram showing the configuration of a bandgap reference voltage generating circuit according to the second embodiment. The same reference numerals are used for configurations corresponding to those in the previously described embodiments, and duplicated descriptions are given only when necessary. The same applies hereinafter.

[0036] This embodiment has an inverted Darlington pair 20A, 20B. The inverted Darlington pair 20A has an NPN BJT 11 whose base is connected to a node N1, and a PNP BJT 13. The emitter of the PNP BJT 13 is connected to a node N2. The collector of the PNP BJT 13 and the emitter of the NPN BJT 11 are connected to a node N4. The emitter-collector path of the PNP BJT 13 is connected between the node N2 and the node N4. The base of the PNP BJT 13 is connected to the emitter of the NPN BJT 11, and the PNP BJT 13 amplifies the output current of the NPN BJT 11. The base resistor of the PNP BJT 13 is omitted for convenience. The inverted Darlington pair may be called a Sziklai pair.

[0037] The inverted Darlington pair 20B has an NPN BJT 21 whose base is connected to a node N1, and a PNP BJT 23. The emitter of the PNP BJT 23 is connected to a node N3. The emitter of the NPN BJT 21 and the collector of the PNP BJT 23 are connected to a node N4 via a resistor R3. The emitter-collector path of the PNP BJT 23 is connected between the nodes N3 and N4. The base of the PNP BJT 23 is connected to the collector of the NPN BJT 21, and the PNP BJT 23 amplifies the output current of the NPN BJT 21. The base resistor of the PNP BJT 23 is omitted for convenience.

[0038] The current gain of the inverted Darlington pair 20A is expressed as β1·β2+β1, where β1 is the current gain of the NPN BJT 11 and β2 is the current gain of the PNP BJT 13. Similarly, the current gain of the inverted Darlington pair 20B is expressed as β1·β2+β1, where β1 is the current gain of the NPN BJT 21 and β2 is the current gain of the PNP BJT 23. Therefore, the reference voltage V REF is expressed by substituting β1·β2+β1 for β in the above-mentioned equation (4). Therefore, the effect of the base resistance RB can be reduced, and the reference voltage V REF Improved temperature characteristics of the reference voltage V REFIt is possible to supply

[0039] According to this embodiment, by using the inverted Darlington pair 20A and 20B, the influence of the base resistance RB is reduced, and a stable reference voltage V REF According to this embodiment, it is possible to provide a bandgap reference voltage generating circuit that outputs the reference voltage V REF is the sum of the base-emitter voltage of the NPN BJT 11 that constitutes the inverted Darlington pair 20A and the voltage drop across the resistor R4. Therefore, for example, the reference voltage V REF Since the current gain β is somewhat lower than in the first embodiment having a Darlington pair, the effect of reducing the influence of the base resistance RB is somewhat lower, but the reference voltage V REF This is suitable for obtaining

[0040] (Third embodiment) 4 is a diagram showing the configuration of a bandgap reference voltage generating circuit according to the third embodiment. This embodiment has a Darlington pair 10A.

[0041] This embodiment has a resistor R3 connected between the emitter of the NPN BJT 21 and the base of the NPN BJT 24 that constitutes the Darlington pair 10C. The emitter-collector path of the NPN BJT 24 is connected between the node N3 and the node N4. The base of the NPN BJT 24 is connected to the emitter of the NPN BJT 21 via the resistor R3, and the NPN BJT 24 amplifies the output current of the NPN BJT 21. The base resistor of the NPN BJT 24 is omitted for convenience.

[0042] The NPN BJTs 21 and 24 have emitter areas N times larger than those of the NPN BJTs 11 and 12.

[0043] In this embodiment, NPN BJTs 11 and 12 form a Darlington pair 10A, and NPN BJT 12 amplifies the output current of NPN BJT 11. NPN BJTs 21 and 24 form a Darlington pair 10C, and NPN BJT 24 amplifies the output current of NPN BJT 21. Therefore, similar to the first embodiment described above, the current gain β of the Darlington pair 10A, 10C is β1·β2+β1+β2, and the influence of the base resistance RB can be reduced. Also, by adjusting the ratio of resistors R3 and R4, the reference voltage V REF The temperature coefficient can be adjusted.

[0044] (Fourth embodiment) 5 is a diagram showing the configuration of a bandgap reference voltage generating circuit according to a fourth embodiment. This embodiment has an inverted Darlington pair 20A.

[0045] This embodiment has a resistor R3 connected between the emitter of the NPN BJT 21 constituting the inverted Darlington pair 20C and a node N4. The emitter-collector path of the PNP BJT 25 is connected between the nodes N3 and N4. The base of the PNP BJT 25 is connected to the collector of the NPN BJT 21, and the PNP BJT 25 amplifies the output current of the NPN BJT 21. The base resistor of the PNP BJT 25 is omitted for convenience.

[0046] The PNP BJT 25 and the NPN BJT 21 have emitter areas N times larger than those of the PNP BJT 13 and the NPN BJT 11, respectively.

[0047] In this embodiment, the NPN BJT 11 and the PNP BJT 13 constitute an inverted Darlington pair 20A, and the PNP BJT 13 amplifies the output current of the NPN BJT 11. The NPN BJT 21 and the PNP BJT 25 constitute an inverted Darlington pair 20C, and the PNP BJT 25 amplifies the output current of the NPN BJT 21. Therefore, similar to the second embodiment described above, the current gain β of the inverted Darlington pair 20A, 20C is β1·β2+β1, and the influence of the base resistance RB can be reduced. Also, by adjusting the ratio of the resistance values ​​of the resistors R3 and R4, the reference voltage V REF The temperature coefficient can be adjusted.

[0048] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0049] 1 power supply line, 2 differential amplifier circuit, 3 output terminal, 10A, 10B, 10C Darlington pair, 20A, 20B, 20C inverted Darlington pair, R1 to R4 resistors, N1 to N4 nodes.

Claims

1. a first node connected to the output; a second node connected to the first current source; a third node connected to the second current source; a fourth node; and a first bipolar junction transistor having a base connected to the first node; a second bipolar junction transistor having a base connected to the first node; a third bipolar junction transistor having an emitter-collector path connected between the second node and the fourth node, the third bipolar junction transistor amplifying an output current of the first bipolar junction transistor; a fourth bipolar junction transistor having an emitter-collector path connected between the third node and the fourth node, the fourth bipolar junction transistor amplifying an output current of the second bipolar junction transistor; a first resistor constituting the first current source; a second resistor constituting the second current source; a third resistor having one end connected to the emitter of the second bipolar junction transistor and the other end connected to the base of a fourth bipolar junction transistor; a fourth resistor having one end connected to the fourth node and the other end grounded; A bandgap reference voltage generating circuit comprising:

2. 2. The bandgap reference voltage generating circuit according to claim 1, wherein the first and third bipolar junction transistors form a first Darlington pair, and the second and fourth bipolar junction transistors form a second Darlington pair.

3. a differential amplifier circuit that supplies an output signal corresponding to a difference between voltage drops occurring across the first resistor and the second resistor to the first node; 3. The bandgap reference voltage generating circuit according to claim 1, further comprising:

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