CN108345336B - Energy gap reference circuit - Google Patents
Energy gap reference circuit Download PDFInfo
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- CN108345336B CN108345336B CN201710058122.XA CN201710058122A CN108345336B CN 108345336 B CN108345336 B CN 108345336B CN 201710058122 A CN201710058122 A CN 201710058122A CN 108345336 B CN108345336 B CN 108345336B
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- 238000010586 diagram Methods 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/10—Regulating voltage or current
- G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
- G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
- G05F1/561—Voltage to current converters
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- Control Of Electrical Variables (AREA)
Abstract
The bandgap reference circuit includes a first operational amplifier, a second operational amplifier, a first current source, a second current source, a third current source, a first bipolar transistor, a second bipolar transistor, a feedback element and a voltage divider circuit. The voltage dividing circuit is used for dividing a voltage difference value between an input of the second operational amplifier and a base of the second bipolar transistor so as to provide a reference voltage.
Description
Technical Field
The invention relates to an energy gap reference circuit.
Background
The bandgap reference circuit is used for generating an accurate output voltage. The output voltage generated by the bandgap reference circuit is not affected by process, power supply and temperature variations. Therefore, the bandgap reference circuit can be widely used in various analog circuits and digital circuits, which require accurate reference voltage during operation.
Fig. 1 illustrates a conventional bandgap reference circuit 100. Referring to fig. 1, the bandgap reference circuit 100 includes PMOS transistors M1, M2, and M3, an operational amplifier OP, resistors R1 and R2, and bipolar transistors Q1, Q2, and Q3. When the base current is ignored, the output voltage VOUT of the bandgap reference circuit 100 can be expressed as:
wherein VEB3 is the voltage difference between the emitter and the base of the bipolar transistor Q3, VT is the thermal voltage (thermal voltage) at room temperature, and N is the ratio of the current density of the bipolar transistor Q2 to the current density of the bipolar transistor Q1.
After adjusting the resistance ratio of the resistors R2 and R1, the bandgap reference circuit 100 can provide a stable output voltage VOUT with zero temperature coefficient, as shown in equation (1). The voltage VOUT has a voltage level of about 1.25V, which is close to an electron volt (electron volt) of the silicon bandgap (energy gap), i.e., the silicon bandgap reference voltage.
However, in order to be widely used in different applications, the bandgap reference circuit may need to output different voltage levels.
Disclosure of Invention
An objective of the present invention is to provide a bandgap reference circuit for providing a reference current and a reference voltage.
According to an embodiment of the present invention, the bandgap reference circuit includes a first operational amplifier, a second operational amplifier, a first current source, a second current source, a third current source, a first bipolar transistor, a second bipolar transistor, a feedback element and a voltage divider circuit. The first operational amplifier has a first input, a second input and a first output. The second operational amplifier has a third input, a fourth input and a second output. The first current source is coupled between a supply power node and the first input of the first operational amplifier. The second current source is coupled between the supply power node and the second input of the first operational amplifier. The third current source is coupled between the supply power node and the third input of the second operational amplifier. The first bipolar transistor has a base with an emitter coupled to the first current source and a collector coupled to a ground node. The second bipolar transistor has a base coupled to the base of the first bipolar transistor, has an emitter, and has a collector coupled to the ground node. The feedback element is coupled between the third current source and the base of the second bipolar transistor, the feedback element being controlled by the second output of the second operational amplifier. The voltage divider circuit is configured to divide a voltage difference between the third input of the second operational amplifier and the base of the second bipolar transistor to provide a reference voltage. The fourth input of the second operational amplifier is coupled to one of the first input of the first operational amplifier and the second input of the first operational amplifier.
Drawings
Fig. 1 illustrates a conventional bandgap reference circuit.
FIG. 2 shows a circuit diagram of a bandgap reference circuit incorporating an embodiment of the invention.
FIG. 3 shows a circuit diagram of a bandgap reference circuit incorporating another embodiment of the present invention.
FIG. 4 shows a circuit diagram of a bandgap reference circuit incorporating yet another embodiment of the present invention.
FIG. 5 shows a circuit diagram of a bandgap reference circuit incorporating yet another embodiment of the present invention.
[ notation ] to show
100 bandgap reference circuit
200 energy gap reference circuit
22 current source unit
24 voltage division circuit
300 energy gap reference circuit
400 energy gap reference circuit
500 energy gap reference circuit
M1, M2, M3 and M4 PMOS transistors
M5 NMOS transistor
OP operational amplifier
OP1, OP2 operational amplifier
Q1, Q2, Q3 bipolar transistor
R1, R2, R3 and R4 resistors
Detailed Description
Fig. 2 shows a circuit diagram of a bandgap reference circuit 200 incorporating an embodiment of the invention. As shown in fig. 2, the bandgap reference circuit 200 includes a current source unit 22, an operational amplifier OP1, an operational amplifier OP2, a resistor R1, a bipolar transistor Q1, a bipolar transistor Q2, a feedback transistor M4, a voltage divider 24 and a resistor R4.
The current source unit 22 provides a plurality of stable bias currents I1, I2, and I3. In the present embodiment, the current source unit 22 is configured as a current mirror, and is composed of three PMOS transistors M1, M2, and M3. Referring to fig. 2, the PMOS transistor M1 has a source coupled to a supply voltage source VDD, a gate coupled to an output terminal of the operational amplifier OP1, and a drain coupled to an inverting input terminal of the operational amplifier OP 1. The PMOS transistor M2 has a source coupled to the supply voltage source VDD, a gate coupled to the output terminal of the operational amplifier OP1, and a drain having a non-inverting input terminal coupled to the operational amplifier OP1 and a non-inverting input terminal coupled to the operational amplifier OP 2. The PMOS transistor M3 has a source coupled to the supply voltage source VDD, a gate coupled to the output terminal of the operational amplifier OP1, and a drain coupled to an inverting input terminal of the operational amplifier OP 2.
The bipolar transistor Q1 has a base for receiving a bias voltage VB, an emitter coupled to an inverting input of the operational amplifier OP1, and a collector coupled to a ground terminal. The bipolar transistor Q2 has a base for receiving the bias voltage VB and a collector coupled to the ground terminal. The resistor R1 is coupled between a non-inverting input terminal of the operational amplifier OP1 and the emitter of the bipolar transistor Q2.
Referring to fig. 2, the feedback transistor M4 is a PMOS transistor having a source coupled to the inverting input of the operational amplifier OP2, a gate coupled to an output of the operational amplifier OP2, and a drain coupled to the base of the bipolar transistor Q1 and the base of the bipolar transistor Q2. The voltage dividing circuit 24 is connected in parallel with the feedback transistor M4. The resistor R4 is coupled between the voltage divider circuit 24 and the ground terminal.
Referring to fig. 2, the operational amplifier OP1 and the current source unit 22 form a negative feedback loop, so that the input voltages VD1 and VD2 are substantially the same. Thus, the voltages VD1 and VD2 can be expressed as:
VD1＝VD2＝VB+VEB1＝VB+VEB2+I2×R1 (2)
wherein, VEB1 is the emitter-base voltage difference of the bipolar transistor Q1, and VEB2 is the emitter-base voltage difference of the bipolar transistor Q2.
Accordingly, equation (2) can be rearranged as:
referring to fig. 2, the operational amplifier OP2, the current source unit 22 and the feedback transistor M4 form a negative feedback loop, so that the input voltages VD2 and VD3 are substantially the same. Since the gates of the transistors M1, M2 and M3 are connected to each other, the sources of the transistors M1, M2 and M3 are coupled to the supply voltage source VDD, and the drain voltages of the transistors M1, M2 and M3 are substantially the same, the current values of the currents I1, I2 and I3 flowing through the PMOS transistors M1, M2 and M3 are proportional to the width-to-length ratio of the transistors.
In the present embodiment, the width-to-length ratio of the PMOS transistors M1, M2, and M3 is set to 1:1: M, where M is a positive integer. Therefore, the current values of the current I1 and the current I2 are substantially the same, and the current value of the current I3 is m times the current I1.
For simplicity, the voltage divider circuit 24 in fig. 2 is composed of two resistors R2 and R3 connected in series, however, the present invention should not be limited thereto. In the present embodiment, the voltage dividing circuit 24 divides the voltage difference between the voltage VD3 and the voltage VB to provide a reference voltage VREF at the crossing point of the resistor R2 and the resistor R3. Thus, equation (3) can be rearranged to equation (4):
since the emitter-base voltage difference of the bipolar transistor Q1 has a negative temperature coefficient and the voltage difference △ VBE has a positive temperature coefficient, the temperature coefficient of the voltage value of the reference voltage VREF can be adjusted to be a positive value, a negative value or substantially equal to zero.
Referring to fig. 2, the operational amplifiers OP1 and OP2 make the voltages VD1, VD2 and VD3 substantially the same by a negative feedback loop. In other embodiments of the present invention, in order to make the voltages VD1, VD2 and VD3 substantially the same, the non-inverting input of the operational amplifier OP2 can receive the voltage VD1, as shown in fig. 3. In addition, referring to fig. 4, the feedback transistor M5 is an NMOS transistor having a drain coupled to the non-inverting input terminal of the operational amplifier OP2, a gate coupled to the output terminal of the operational amplifier OP2, and a source coupled to the base of the bipolar transistor Q1. In order to make the voltages VD1, VD2 and VD3 substantially the same, the inverting input of the operational amplifier OP2 can be coupled to the PMOS transistor M2 or to the PMOS transistor M1.
Referring back to fig. 1, the voltage level of the stable output voltage VOUT with zero temperature coefficient provided by the conventional bandgap reference circuit is about 1.25V. However, the bandgap reference circuit disclosed in the present invention can provide an output voltage with a lower voltage level. Taking fig. 2 as an example, when the resistance of the resistor R2 in the voltage divider circuit 24 is the same as the resistance of the resistor R3, the voltage level of the stable output voltage VREF with zero temperature coefficient provided by the bandgap reference circuit 200 can be as low as 0.63V by properly selecting the value of m or the ratio of the resistor R4 to the resistor R1, since the voltage level of VREF is reduced by multiplying VEB1 in formula (4) by R3/(R2+ R3).
The bandgap reference circuit 200 shown in fig. 2 provides a stable output voltage VREF to internal circuitry. However, the present invention should not be limited thereto. Referring to fig. 5, the bandgap reference circuit 500 provides a stable output current IREF to the internal circuit. The temperature coefficient of the output current IREF can be adjusted according to equation (3) by selecting the temperature coefficient of the resistor R1 or changing the width-to-length ratio of the PMOS transistor M3 to the PMOS transistor M2.
While the technical content and the technical features of the invention have been disclosed, those skilled in the art can make various substitutions and modifications based on the teaching and the disclosure of the invention without departing from the spirit of the invention. Therefore, the scope of the present invention should not be limited to the embodiments disclosed, but includes various alternatives and modifications without departing from the present invention, which is encompassed by the appended claims.
Claims (10)
1. An energy gap reference circuit comprising:
a first operational amplifier having a first input, a second input and a first output;
a second operational amplifier having a third input, a fourth input, and a second output;
a first current source coupled between a supply power node and the first input of the first operational amplifier;
a second current source coupled between the supply power node and the second input of the first operational amplifier;
a third current source coupled between the supply power node and the third input of the second operational amplifier;
a first bipolar transistor having a base, having an emitter coupled to the first current source, and having a collector coupled to a ground node;
a second bipolar transistor having a base coupled to the base of the first bipolar transistor, having an emitter, and having a collector coupled to the ground node;
a feedback element coupled between the third current source and the base of the second bipolar transistor, the feedback element being controlled by the second output of the second operational amplifier; and
a voltage divider circuit for dividing a voltage difference between the third input of the second operational amplifier and the base of the second bipolar transistor to provide a reference voltage;
wherein the fourth input of the second operational amplifier is coupled to one of the first input of the first operational amplifier and the second input of the first operational amplifier.
2. The bandgap reference circuit of claim 1, further comprising a second resistor coupled between the base of the second bipolar transistor and the ground node.
3. The bandgap reference circuit of claim 2, wherein the voltage divider circuit comprises:
a plurality of resistors connected in series between the third input of the second operational amplifier and the base of the second bipolar transistor to provide the reference voltage.
4. The bandgap reference circuit of claim 2, wherein said feedback element is a PMOS transistor having a drain coupled to said base of said first bipolar transistor, a source coupled to said third input of said second operational amplifier, and a gate coupled to said second output of said second operational amplifier.
5. The bandgap reference circuit of claim 2, wherein said feedback element is an NMOS transistor having a source coupled to said base of said first bipolar transistor, a drain coupled to said third input of said second operational amplifier, and a gate coupled to said second output of said second operational amplifier.
6. The bandgap reference circuit of claim 2, wherein the positive temperature coefficient of the reference voltage is obtained by increasing the ratio of the current value of the third current source to the current value of the second current source.
7. The bandgap reference circuit of claim 2, wherein the positive temperature coefficient of the reference voltage is obtained by increasing the ratio of the resistance of the second resistor to the resistance of the first resistor.
8. The bandgap reference circuit of claim 3, wherein a negative temperature coefficient of said reference voltage is obtained by adjusting a resistance of said resistor in said voltage divider circuit.
9. The bandgap reference circuit of claim 2, wherein said reference voltage is less than 1.25V.
10. The bandgap reference circuit of claim 2, wherein said reference voltage is equal to 0.63V.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710058122.XA CN108345336B (en) | 2017-01-23 | 2017-01-23 | Energy gap reference circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201710058122.XA CN108345336B (en) | 2017-01-23 | 2017-01-23 | Energy gap reference circuit |
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| Publication Number | Publication Date |
|---|---|
| CN108345336A CN108345336A (en) | 2018-07-31 |
| CN108345336B true CN108345336B (en) | 2020-04-28 |
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Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20210121688A (en) | 2020-03-31 | 2021-10-08 | 에스케이하이닉스 주식회사 | Reference voltage circuit |
| CN113934252B (en) * | 2020-07-13 | 2022-10-11 | 瑞昱半导体股份有限公司 | Voltage reduction circuit for energy gap reference voltage circuit |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI331265B (en) * | 2007-01-22 | 2010-10-01 | Faraday Tech Corp | Bandgap reference circuit |
| TWI382292B (en) * | 2009-05-07 | 2013-01-11 | Aicestar Technology Suzhou Corp | Bandgap circuit |
| TWI521326B (en) * | 2013-12-27 | 2016-02-11 | 慧榮科技股份有限公司 | Bandgap reference generating circuit |
| CN105300464B (en) * | 2014-07-02 | 2019-02-15 | 晶豪科技股份有限公司 | Energy band gap reference circuit |
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