JPH0573163A - Voltage generation circuit - Google Patents

Abstract

PURPOSE:To generate the voltage source capable of obtaining an arbitrary intermediate potential, canceling the temperature characteristic and performing the absorption and distortion with low power consumption and with few fluctuation due to the condition of load. CONSTITUTION:The circuit is composed of a means for generating the intermediate potential consisting of a constant voltage generating the intermediate potential from a pair of power supply terminals 1 and 2 and resistance 4 and a buffer circuit consisting of transistors 9 and 10 connecting a pair of complementary emitters to be supplied from this intermediate potential as the intermediate power supply of the other circuit by resistance 17 and 18. Between the bases of a pair of transistors 9 and 10, as many as diodes 11 and 12 are connected in the forward direction of the base emitter of a pair of transistors 9 and 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage generating circuit, and more particularly to an intermediate potential voltage generating circuit capable of sucking and sweeping.

[0002]

2. Description of the Related Art An example of a conventional voltage generating circuit of this type is
As shown in FIG. For example, in a subscriber circuit of an electronic exchange, the power supply voltage is 48 V as a standard, which is very large. Therefore, the operational amplifiers 5 and 6 constituting the subscriber circuit are connected to the power supply lines of the operational amplifiers 5 and 6 in FIG. 3 in order to maintain the circuit withstand voltage and to reduce the power consumption due to the large power supply voltage. Similarly, it is often connected vertically.

That is, in a conventional example, a power source connected between terminals 1 and 2 generates an intermediate potential by a constant voltage generating circuit 3 and a resistor 4 which are a combination of Zener diodes, diodes, etc. The high power supply side is connected to the power supply terminal 1, the low power supply side is connected to the intermediate potential, the high power supply side of the operational amplifier 6 is connected to the intermediate potential, and the low power supply side is connected to the power supply terminal 2.

Next, another example of the conventional voltage generating circuit of this type is shown in FIG. The power supply connected between the terminals 1 and 2 generates an intermediate potential by the constant voltage generating circuit 3 and the resistor 4,
Further, after dividing the voltage to an arbitrary potential by the resistors 7 and 8, the voltage was buffered by the transistors 9 and 10 and served as a power source for the vertical connection of the operational amplifiers 5 and 6.

[0005]

In one example of the above-mentioned conventional voltage generating circuit, the potential of the vertically-stacked connection portion is determined by the constant voltage generating circuit 3. Therefore, in order to obtain an arbitrary intermediate potential, a Zener diode is required. However, the combination of the diode and the diode becomes complicated, and it is difficult to cancel the temperature characteristic, which is not practical.

For example, in order to generate an intermediate potential of 10V when viewed from the power supply terminal 2, assuming that the breakdown voltage of the Zener diode is 7V and the forward voltage of the diode is 0.65V,
A combination of one Zener diode and five diodes has a voltage of 10.25 V, and the temperature characteristic is poor at about -8 mV / ° C for four diodes.

Further, depending on the states of the operational amplifiers 5 and 6,
Since the power source for the vertically stacked connection portion may be for both suction and sweeping out, a sufficient idling current is required for the constant voltage generation circuit 3 and the resistor 4, which also has the drawback of increasing power consumption.

For example, assuming that the operational amplifier 5 is in the power-down mode and only the operational amplifier 6 is in the active mode and 1 mA is sucked from the high power source side, in order to be able to supply 1 mA from the resistor 4, it is always 1. An idling current of about 5 mA is required, and 48 between terminals 1 and 2
If V is applied, a power consumption of 72 mW is always generated, which is not preferable especially in a subscriber circuit having a large number of circuits.

Next, in another example of the conventional voltage generating circuit, in view of the drawbacks of the conventional example described above, the resistors 7 and 8 and the idling current for obtaining an arbitrary potential are about 1/10 of the example. Although the number of buffer transistors 9 and 10 required is small, there is a drawback in that the voltage changes due to the suction / sweeping of the vertically stacked connection portion which changes depending on the states of the operational amplifiers 5 and 6.

That is, during suction, the transistor 9 is cut off (OFF) and the transistor 10 is turned on (ON). Therefore, the potential determined by the resistors 7 and 8 is 0.65V.
The voltage rises, and the transistor 9 is turned on and the transistor 10 is turned off at the time of sweeping, so that the potential drops by 0.65 V from the potential determined by the resistors 7 and 8.

Accordingly, switching causes a total voltage change of 1.3V, which is not preferable. further,
If this is steadily repeated, it also has a drawback that noise is generated in the output, depending on the performance of the power supply noise rejection ratio of the operational amplifier.

An object of the present invention is to provide a voltage generating circuit which solves the above-mentioned drawbacks, improves temperature characteristics, reduces power consumption and noise characteristics.

[0013]

According to the structure of a voltage generating circuit of the present invention, first and second amplifiers are vertically connected between first and second power supply terminals, and the first and second amplifiers are connected. A buffer is interposed between the common power source connection point of the above and the output of the constant voltage generating circuit, and a diode is connected to the base of the transistor included in the buffer so as to reduce the characteristic variation. To do.

[0014]

1 is a circuit diagram showing a voltage generating circuit according to an embodiment of the present invention.

In FIG. 1, a diode 1 is used in this embodiment.
1, 12, resistors 7, 8, 17, 18, npn transistor 9, pnp transistor 10, and others are the same as in FIG.

In FIG. 1, in the voltage generating circuit according to one embodiment of the present invention, the voltage applied to the power supply terminals 1 and 2 causes an intermediate potential to be generated by the constant voltage generating circuit 3 and the resistor 4, and further the resistor 7 is used. , 8 and diodes 11, 12 divide the voltage to an arbitrary voltage and supply it to the bases of the transistors 9, 10.

Since the diodes 11 and 12 are connected between the bases of the transistors 9 and 10, the transistors 9 and 10 are not completely cut off (OFF).

That is, almost no voltage fluctuation occurs due to suction / sweeping. For example, the resistors 17 and 18 for setting the idling current are set to 50Ω, respectively,
Assuming that each sweep current is 1 mA, 0.1
Only a fluctuation of about V, which is a great improvement.

FIG. 2 is a circuit diagram showing a voltage generating circuit according to another embodiment of the present invention.

In FIG. 2, a diode 1 is used in this embodiment.
1, 12, 13, 14, resistances 17, 18, npn transistors 9, 15, and pnp transistors 10, 16 are provided, and the others are the same as in FIG.

In FIG. 2, if the operational amplifiers 5 and 6 require a high band, for example, the operational amplifiers 5 and 6 are inevitably used.
The power supply current of 6 also increases.

That is, since the sinking / sweeping current also increases, the base current cannot be ignored with one transistor, and an error will occur in an arbitrary voltage generated by the resistors 7 and 8.

As a countermeasure against this, as shown in FIG. 2, by adding transistors 15 and 16 and connecting the transistors 9 and 10 to Darlington, the influence of the base current can be ignored.

[0024]

As described above, according to the present invention, in particular, the same number of diodes are connected between the bases of a pair of complementary transistors in the same direction as the forward direction of the base-emitters of the transistors. Is generated, the power consumption is low, the voltage fluctuation due to the load condition is small, and the power supply generation circuit of the intermediate potential capable of canceling the temperature characteristic can be easily realized.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a voltage generating circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a voltage generating circuit according to another embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional voltage generation circuit.

FIG. 4 is a circuit diagram showing another conventional example.

[Explanation of symbols]

 1, 2 Power supply terminal 3 Constant voltage generation circuit 4 Bias resistor 5,6 Operational amplifier (load) 7,8 Voltage dividing resistor 9,10 Buffer transistor 11, 12, 13, 14, Diode 15,16 Darlington transistor

Claims (2)

[Claims] 1. A first power supply terminal and a second power supply terminal are vertically stacked and connected between a first power supply terminal and a second power supply terminal, and a common power supply connection point of the first and second amplifiers and an output of a constant voltage generation circuit. A voltage generating circuit characterized in that a buffer is interposed therebetween and a diode is connected to a base of a transistor included in the buffer so as to reduce characteristic fluctuation. 2. The voltage generating circuit according to claim 1, wherein the transistors are Darlington-connected.