JPH05127766A - Band gap constant voltage circuit - Google Patents

Abstract

PURPOSE:To obtain the band gap constant voltage circuit which consists of a small number elements and is small in the number of elements whose ratio is to be calculated. CONSTITUTION:An operational amplifier 10 generates an input offset voltage which is proportional to temperature. This input offset voltage is amplified to become a voltage having positive temperature characteristics, and this voltage and a voltage with negative temperature characteristics which is generated by a diode 11 are added together to obtain a voltage which does not depend upon the temperature. Consequently, a voltage having opposite temperature characteristics from a voltage with negative temperature characteristics which is developed across a diode 11 need not be generated by providing elements other than the operational amplifier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bandgap constant voltage circuit for generating a voltage having no temperature dependence.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram showing a conventional bandgap constant voltage circuit. In the figure, 1 is an operational amplifier having an offset voltage of almost 0. A diode 2 is connected between the non-inverting terminal of the operational amplifier 1 and the ground. The inverting terminal of the operational amplifier 1 is grounded via the series circuit body of the resistor 3 and the diode 4. Output terminal 1 of operational amplifier 1
00 is connected to the non-inverting terminal via the resistor 5 and is also connected to the inverting terminal via the resistor 6.

Now, the resistance values of the resistors 3, 5 and 6 are respectively set to R3.
R5, R6, the inverting terminal voltage is V1b, the non-inverting terminal voltage is V2b, the voltage of the output terminal 100 is V3b, and the currents flowing through the diodes 2 and 4 are I2 and I4, respectively. Also,
Assuming that the PN junction area ratio of the diodes 2 and 4 is 1: X and the voltages generated in the diodes 2 and 4 are V2 and V4, respectively, V2 = (kT / q) · ln (I2 / Is) V4 = (kT / q) · ln {I4 / (X · Is)}. Where k is the Boltzmann constant, T is the absolute temperature,
q is the charge of the electron, and Is is the reverse saturation current of the diode.

FIG. 6 is a circuit diagram showing a specific configuration example of the operational amplifier 1 in the circuit shown in FIG. The diodes 2 and 4 in FIG. 5 are composed of diode-connected NPN transistors. The operational amplifier 1 includes PNP transistors 20, 21, 25, an NPN transistor 22B,
23, 24, 26, constant current sources 27, 28, capacitor 2
It consists of 9.

Transistors 20 and 21 form a differential pair. The common connection point of the emitters of the transistors 20 and 21 is connected to the power supply via the constant current source 27. The base of the transistor 20 is connected to a common connection point of the resistor 5 and the diode 2 (diode-connected transistor). The base of the transistor 21 is connected to the common connection point of the resistors 3 and 6.

The transistor 22B and the transistor 23 form a current mirror circuit using the transistor 22B as a reference transistor. The emitter area ratio of the transistor 22B and the transistor 23 is 1: 1. The emitter area ratio of the transistor 22B and the transistor 23 is 1: 1.
Is set so that the input offset voltage of the operational amplifier 1 becomes almost zero. Transistor 22B
Has a collector connected to the collector of the transistor 20, an emitter connected to ground, and a base connected to its own collector. The transistor 23 has a collector connected to the collector of the transistor 21, an emitter connected to ground, and a base connected to the base of the transistor 22B. The capacitor 29 is a capacitor for preventing oscillation and is connected between the base and collector of the transistor 23.

The transistor 24 is diode-connected,
The collector is connected to the power supply via the constant current source 28. The transistor 25 has a base connected to the collector of the transistor 23, an emitter connected to the emitter of the transistor 24, and a collector connected to the ground. The transistor 26 has a collector as a power source and an emitter as an output terminal 10.
0, the base is connected to the collector of transistor 24, respectively.

Next, the operation will be described. Diode 2
Voltage V2 ((kT / q) .ln (I2 / I
s)) is the non-inverting terminal voltage V2b of the operational amplifier 1 as it is.
Becomes On the other hand, the voltage V4 ((k
The sum of T / q) · ln {I4 / (X · Is)}) and the voltage V3 (= I4 · R3) generated in the resistor 3 becomes the inverting terminal voltage V1b. The inverting terminal voltage V1b operates so as to be equal to the non-inverting terminal voltage V2b by the principle of imaginary short circuit. That is, (kT / q) · ln (I2 / I
s) = (kT / q) · ln {I4 / (X · Is)} + I
Operates to become 4R3. When I2 = I4 = I is set, the voltage V3 (= I4 · R3) becomes (kT /
q) · lnX. That is, when I2 = I4 = I is set, the voltage V3 becomes a voltage proportional to the temperature regardless of the current I.

Inversion terminal voltage V1b, non-inversion terminal voltage V2
b changes at a rate of about −2 mA / ° C. according to the temperature change.
Therefore, when the voltage V3 is converted into a current by the resistor 3 and the current is passed through the resistor 6, the voltage V3 is further converted into a voltage V6 which is R6 / R3 times (voltage drop in the resistor R6).
If the temperature characteristic of 6 is set to have a temperature characteristic opposite to that of the inverting terminal voltage V1b, the voltage V3b of the output terminal 100 is set.
Is a voltage that does not depend on temperature changes. Also, resistors 3, 6
The voltage V3b is adjusted to about 2Vbe by adjusting the resistance value of
(Vbe is the voltage drop across the diode).

[0010]

Since the conventional bandgap constant voltage circuit is constructed as described above, it is complicated because it has a large number of elements, and it is necessary to obtain the resistance ratio and the PN junction area ratio of the diode. There was a problem.

The present invention has been made to solve the above problems, and an object thereof is to obtain a bandgap constant voltage circuit having a small number of elements and a small number of elements taking a ratio.

[0012]

A voltage generating circuit according to the present invention has an operational amplifier that generates an input offset voltage proportional to temperature and a diode, and is obtained by amplifying the input offset voltage of the operational amplifier. It is characterized in that a voltage independent of temperature is obtained by adding a first voltage having a positive temperature characteristic and a second voltage having a negative temperature characteristic generated in the diode.

[0013]

In the present invention, by adding the first voltage having the positive temperature characteristic obtained by amplifying the input offset voltage of the operational amplifier and the second voltage having the negative temperature characteristic generated in the diode, Since the voltage that does not depend on the temperature is obtained, it is not necessary to generate a voltage having a temperature characteristic opposite to the second voltage having a negative temperature characteristic generated in the diode by a device other than the operational amplifier.

[0014]

1 is a circuit diagram showing an embodiment of a bandgap constant voltage circuit according to the present invention. In the figure, 10
Is the input offset voltage (kT / q) · l proportional to temperature
It is an operational amplifier that generates nA. The non-inverting terminal of the operational amplifier 10 is grounded via the diode 11. The resistor 12 is connected between the inverting terminal and the non-inverting terminal. The output terminal 100 of the operational amplifier 10 is connected to the inverting terminal via the resistor 13.

FIG. 2 is a circuit diagram showing a specific circuit configuration of the operational amplifier 10 shown in FIG. The difference from the conventional operational amplifier shown in FIG. 6 is that the transistor 22B is replaced with a transistor 22A. Transistor 22
Unlike the conventional case, the emitter area ratio of A to the transistor 23 is set to A: 1. The other configuration of the operational amplifier 10 is the same as that of the conventional circuit shown in FIG.

First, the operation in which the input offset voltage of the operational amplifier 10 becomes (kT / q) · lnA will be described with reference to FIG. It is assumed that the same voltage is input to the bases of the transistors 20 and 21. At this time, the transistor 25
Ignoring the base current of, the current from the constant current source 27 is divided into A: 1 by the transistors 22A and 23. Therefore, a potential difference of (kT / q) · lnA occurs between the inverting terminal voltage V1a and the non-inverting terminal voltage V2a, and this potential difference becomes the input offset voltage.

Next, assuming that the current flowing through the diode 11 is I11, the resistance value of the resistor 12 is R12, the resistance value of the resistor 13 is R13, the potential of the output terminal 100 is V3a, and the saturation current of the diode 11 is Is11. , V1a−V2a = (kT / q) · lnA V2a = (kT / q) · ln (I11 / Is11) I11 = (V1a−V2a) / R12 V3a = V1a + I11 · R13. From these equations, V3a = (kT / q) · ln [{A · (kT / q) · l
nA} / (R12 · Is11)] + {R13 · (kT /
q) · lnA} / R12 holds.

The first term on the right side of the above equation is the diode 1
It shows a forward voltage of 1 and its temperature coefficient is about -2 m.
V / ° C. The second term on the right side is a voltage obtained by amplifying the input offset voltage, and is a term for canceling the temperature coefficient of the first term. If the ratio value A and the resistance values R12 and R13 in the second term are set so that the temperature coefficient of the second term is approximately +2 mV / ° C, the output voltage V3a becomes a voltage irrelevant to the temperature change and the output voltage V3a. Can be set to 2Vbe as in the conventional case.

As described above, the voltage having the positive temperature characteristic obtained by amplifying the input offset voltage proportional to the temperature generated by the operational amplifier 10 and the voltage having the negative temperature characteristic generated by the diode 11 are added. Since a voltage that does not depend on the temperature is obtained, it is not necessary to take the ratio of the PN junction area of the diode as in the conventional case, and the number of elements is reduced.

In the above embodiment, (kT / q) .ln
The emitter area ratio of the transistors 22A and 23 was set to A: 1 to generate the input offset voltage of A, but the emitter area ratio of the transistors 22A and 23 was set to 1: 1.
Even if the emitter area ratio of the transistors 20 and 21 is A: 1, the same effect as that of the above embodiment can be obtained.

FIG. 3 is a circuit diagram showing another embodiment of the present invention. In the figure, 30 is an operational amplifier that generates an input offset voltage proportional to temperature. Operational amplifier 30
The output terminal 100 is connected to the inverting terminal, and the resistor 32 and the diode 33 are connected in series between the non-inverting terminal and GND. A resistor 31 is connected between the inverting terminal and the non-inverting terminal.

FIG. 4 is a circuit diagram showing a specific configuration of the operational amplifier 30. The NPN transistors 40 and 41 form a differential pair. The base of the transistor 40 is connected to the common connection point of the resistors 31 and 32, and the emitter is connected to the emitter of the transistor 41. The common emitter connection point of the transistors 40 and 41 is a constant current source 42.
Is connected to GND via. The base of the transistor 41 is connected to the output terminal 100.

The PNP transistors 43 and 44 form a current mirror circuit based on the transistor 43.
The emitter area ratio of the transistors 43 and 44 is set to A: 1. The transistor 43 has an emitter connected to the power supply, a collector connected to the collector of the transistor 40, and a base connected to its own collector. The transistor 44 has an emitter for the power supply, a collector for the collector of the transistor 41, and a base for the transistor 43.
Connected to the base of each. NPN transistor 4
5, the collector is the power supply, the emitter is the output terminal 100
In addition, the bases are connected to the common collector connection points of the transistors 44 and 41, respectively. In the circuit of FIG. 4, the diode 33 shown in FIG. 3 is composed of a diode-connected NPN transistor.

By setting the emitter area ratio of the transistors 43 and 44 to A: 1, the input offset voltage of the operational amplifier 30 is (kT / q) ln as in the above embodiment.
The voltage becomes A and the voltage becomes proportional to the temperature. Even with such a configuration, a voltage that does not depend on temperature is output to the output terminal 100, as in the above embodiment.

In the above embodiment, the transistors 43,
The emitter area ratio of 44 is A: 1 (kT / q) · ln
Although the input offset voltage of A is generated, the same effect as that of the above embodiment can be obtained by setting the emitter area ratio of the transistors 43 and 44 to 1: 1 and the emitter area ratio of the transistors 40 and 41 to A: 1.

Further, the configuration of the operational amplifier 10 shown in FIG. 1 may be the configuration shown in FIG. 4 (the differential input section is an NPN transistor configuration and the active load section is a PNP transistor configuration), and is shown in FIG. The same effect can be obtained even if the configuration of the operational amplifier 30 is the configuration shown in FIG. 2 (the differential input section is the PNP transistor configuration and the active load section is the NPN transistor configuration).

[0027]

As described above, according to the present invention, the first voltage having the positive temperature characteristic obtained by amplifying the input offset voltage of the operational amplifier and the second voltage having the negative temperature characteristic generated in the diode are obtained. Since the voltage that does not depend on the temperature is obtained by adding the voltage of, the voltage having the temperature characteristic opposite to the second voltage having the negative temperature characteristic generated in the diode is generated by the element other than the operational amplifier. There is no need to generate it. As a result, the number of elements decreases and
This has the effect of reducing the number of elements that take a ratio.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a bandgap constant voltage circuit according to the present invention.

2 is a circuit diagram showing a specific circuit configuration of an operational amplifier in the circuit shown in FIG.

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a specific circuit configuration of an operational amplifier in the circuit shown in FIG.

FIG. 5 is a circuit diagram showing a conventional bandgap constant voltage circuit.

6 is a circuit diagram showing a specific circuit configuration of the circuit shown in FIG.

[Explanation of symbols]

 10 Operational amplifier 11 Diode

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[Procedure amendment]

[Submission date] April 2, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

FIG. 2 is a circuit diagram showing a specific circuit configuration of the operational amplifier 10 shown in FIG. The difference from the conventional operational amplifier shown in FIG. 6 is that the transistor 22B is replaced with a transistor 22A. Transistor 22
Unlike the conventional case, the emitter area ratio of A to the transistor 23 is set to A: 1 .

Claims (1)

[Claims] 1. A first voltage having an operational amplifier that generates an input offset voltage proportional to temperature and a diode, the first voltage having a positive temperature characteristic obtained by amplifying the input offset voltage of the operational amplifier, and the diode. A bandgap constant voltage circuit characterized in that a voltage that does not depend on temperature is obtained by adding a second voltage having a negative temperature characteristic that occurs in the circuit.