JPS6074705A - Reference voltage generating circuit - Google Patents

Abstract

PURPOSE:To improve the temperature characteristic of a reference voltage by adoping the constitution that the reference voltage is stabilized with a voltage difference between base-emitter voltage of transistors (TR) having a different emitter area so as to have only to add a few circuit elements. CONSTITUTION:A base and a collector a TR3 are connected to abase of a TR1, and an emitter of the TR3 is connected via a resistor R3. The TR3 has an emitter area being n-time that of the TR1, where (n) is a number >1. When the ambient temperature of the circuit is higher than the set temperature, although the base-emitter voltage VBE of the TR1 is decreased, the voltage difference DELTAVBE between the base-emitter voltages of the TR1, TR2 is larger, an emitter current I2 of the TR3 is increased so as to increase the voltage drop across a resistor R1 thereby preventing the decrease in the reference voltage VR. Thus, fluctuation of the reference voltage VR is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a reference voltage generation circuit, and more particularly to a circuit in which a temperature change in a reference voltage is extremely reduced by a simple circuit configuration of tRj.

Prior Art and Problems FIG. 1 shows an example of a conventional reference voltage generation circuit. The circuit in the figure includes transistors Tr1. It is composed of Tr2, constant current circuit O81, resistors R1 and R2, capacitor 04, and the like.

In the circuit of FIG. 1, the emitter of transistor Tr2,
In other words, the output terminal voltage ■8 is the resistance R4 and R2.
The voltage is divided by and applied to the base of the transistor Tr1. The collector of the transistor Tr1 is connected to the base of the transistor Tr2, and is connected to the power supply Vaa via a constant current circuit O8. Also, the transistor Tr1
The base of is grounded. Therefore, the following equation holds.

2 ■R=vBE R1+ R2 Transforming this formula, we get vi=　11+R,VB,++・＋++　(l.

2 holds true. Here, vBB is the base-emitter pressure of the transistor Trl, and is expressed as follows. Here, KT/(l is the thermal voltage, . is the reverse saturation current, and . is the emitter current. The capacitor 0. is used to remove ripples and noise components of the reference output voltage vR. It is for.

In the conventional circuit shown in FIG. 1, as is clear from equation (1), the temperature characteristics of the reference voltage vR are determined by the temperature coefficient of the base-emitter voltage vBF of the transistor Tr1. Since the temperature coefficient of the base-emitter voltage of a transistor generally takes a fairly large negative value, the conventional circuit shown in FIG. 1 has the disadvantage that the temperature characteristics of the reference voltage vR are not very good.

Purpose of the Invention The purpose of the present invention is to:
In a reference voltage generation circuit, the temperature characteristics of the reference voltage are improved by a simple circuit based on a configuration in which the reference voltage is stabilized using the difference voltage between the base-emitter voltages of transistors having different emitter areas. It is in.

According to the invention, a first transistor whose base is connected to a power supply via a constant current circuit;
The emitter voltage of the transistor is divided and applied to the base, and the collector is connected to the base of the first transistor. It is characterized by comprising a grounded third transistor, outputting a reference voltage from the emitter of the first transistor, and making the emitter area of the third transistor larger than the emitter area of the second transistor. This is accomplished by providing a reference voltage generation circuit.

Examples of the invention Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 2 shows a reference voltage generation circuit according to one embodiment of the present invention. The circuit in the same figure is the same as the circuit in Figure 1 with the transistor T.
r, and a resistor R3 is added. That is, the base and collector of the transistor Tr5 are connected to the base of the transistor Tr, and the emitter of the transistor "r3 is grounded via the resistor R.The other parts are the same as the circuit in FIG. 1, and the same references are used. Note that the transistor Tr5 has an emitter area twice that of the transistor Tr, where Tr is a number greater than one.

FIG. 6 shows the temperature characteristics of the transistor emitter voltage. As is clear from the figure, the base-emitter voltage vBl generally has a negative temperature characteristic, but the larger the emitter area, the larger the absolute value of the temperature coefficient. Therefore, it can be seen that the differential voltage Δv0 between the base-emitter voltages of transistors having different emitter and emitter areas has a positive temperature coefficient. The circuit shown in Figure 2 improves the temperature characteristics by correcting the negative temperature coefficient of the base-emitter voltage by the positive temperature coefficient of the base-emitter voltage difference, and its operation is explained below. do.

That is, in the circuit shown in Fig. 2, when the ambient temperature becomes higher than the set temperature, the pace-emitter voltage VB)i of the transistor Tr decreases, but the transistor T
The difference voltage ΔvB between the base and emitter voltages between r and T□
g increases, and the emitter current x of transistor Tr5
2 increases, increasing the voltage drop across the resistor R1 and preventing the reference voltage vR from dropping.

Therefore, fluctuations in the reference voltage vR are prevented.

Conversely, when the ambient temperature becomes lower than the set temperature, the base-emitter voltage V□ of the transistor Tr increases, but the difference voltage △vB between the base-emitter voltages of the transistors Tr1 and Tr5! , becomes smaller and the emitter current of the transistor Tr3 decreases, thereby preventing the reference voltage vR from rising.

FIG. 4 shows a reference voltage generation circuit according to another embodiment of the present invention. In the circuit shown in the figure, the emitter resistor R1 of the transistor "r2 in FIG. 2 is divided into two resistors R4 and R5, and the collector of the transistor Tr3 is connected to the connection point of these resistors R4 and R5. The other parts are the same as the circuit of FIG. 2 and are designated by the same reference numerals.

In the circuit shown in FIG. 4, the temperature characteristics of the reference voltage vR can be precisely corrected by adjusting the magnitudes of the resistors R4 and R5 to M. That is, it is possible to set the voltage drop that occurs across the resistor R4 to an arbitrary value, and it is possible to precisely adjust the temperature coefficient in conjunction with the a adjustment depending on the area of the emitter of the transistor Tris. It is also clear that the temperature coefficient can be set to any value other than zero.

Effects of the Invention As described above, according to the present invention, it is possible to significantly improve the temperature characteristics of a reference voltage generating circuit by simply adding a very small number of circuit elements to a conventional circuit.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an example of a conventional reference voltage generation circuit, FIG. 2 is an electric circuit diagram showing the configuration of a reference voltage generation circuit according to an embodiment of the present invention, and FIG. FIG. 4 is a graph showing the temperature characteristics of the base-to-emitter voltage and the temperature characteristic of the voltage between the edges, and an electric circuit diagram showing a reference voltage generation circuit according to another embodiment of the present invention. Trj, Tr2. "r5...transistor, O
8... Constant current circuit, R1, R2, RIs, R4, R5°゛°resistance 10,・
...Capacitor. Patent applicant Fujitsu Ltd. Patent application agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Yukio Uchida Patent attorney Akiyuki Yamaguchi Figure 1 Figure 2 Figure 3 Figure 4 [4]

Claims (1)

[Claims] A first transistor whose base is connected to a power supply via a constant current circuit, a second transistor whose emitter voltage is divided and applied to the base, and whose collector is connected to the base of the first transistor. and a sixth transistor whose base is connected to the base of the second transistor and whose emitter is grounded via a resistor,
1. A reference voltage generation circuit, characterized in that a reference voltage is output from the emitter of the first transistor, and the emitter area of the third transistor is made larger than the emitter area of the second transistor.