JPS59189420A - Current inverting circuit - Google Patents

Abstract

PURPOSE:To reduce the minimum operating voltage, and to secure a stable opeation even if terminal voltage drops by providing a constant-current source for setting a reference current, a transistor to which a base current is given by this constant-current source, etc. CONSTITUTION:A constant-current source for setting a reference current, a transistor to which a base current is given by this constant-current source, etc. are provided. For instance, the emitter of a transistor 20 is connected to a power source line to which driving voltage VCC is applied from a power source terminal 22, and a constant-current source 26 is connected between the base and a reference potential terminal 24. Also, basing on a reference constant-current I1 given by a constant-current source 26, a constant base current is supplied to the transistor 20, and a current I3 flowing to the transistor 20 is supplied as a base current to a transistor 28. Subsequently, a current I2 is supplied to the collector of the transistor 28 from the base of a transistor 32, and the current I1 flows to a transistor 34 in a balanced state so that it can be fetched from an output terminal 36.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current inverting circuit, and more particularly to an improvement in a current inverting circuit used as a constant current source on an integrated circuit.

FIG. 1 shows a conventional current inversion circuit constructed on an integrated circuit. That is, the transistor 2 has its base and collector connected in common and is configured as a diode.
It is connected to the base/collector side via a constant voltage source 8 between the power supply line to which c is applied and the ground terminal 6 which sets a reference potential point. Also, the base of transistor 2
The bases of the transistors 100 are commonly connected to the collectors, the emitters of the transistors 10 and the emitters of the transistors 2 are connected to the power supply line, and the collectors are formed with output terminals 12 for taking out the inverted current.

According to such a configuration, when the reference constant current I is applied by the constant current source 8, a constant current ■ flows through the transistor 2 as a diode, and the emitter (anode of the diode) and base collector (anode of the diode) of the transistor 2 are connected. A forward voltage drop vF occurs between the cathode and the cathode. The base-emitter voltage V[]E of the transistor 10 is given by the forward drop voltage vF and is regulated by that value, so a constant voltage source is inserted between the base and emitter of the transistor 10. . Moreover, transistor 10
Since the base current of the transistors 10 is regulated by the constant current source 8, if the electrical characteristics such as the current amplification factor of the transistors 2.10 can be made uniform as in an integrated circuit, each transistor 10.
A constant current I flows through, and this current I can be taken out from the output terminal 12. That is, the currents of transistor 2 and transistor 10 are given the same value, and a current reversal characteristic (current mirror effect) is obtained.

However, since the transistor 2 as a diode and the transistor constituting the constant current source 8 are inserted between the power supply line and the reference potential point, the voltage drop is the forward drop voltage VF and the constant current source 8. It consists of the saturation voltage Vsat of the transistor. Generally, in a monolithic integrated circuit made of silicon, the forward voltage drop vF is 6
60 mV, and Vsat is about 0.2 V, so the combined value is as much as 860 mV, and the operating voltage needs to be at least about 0.9 V. Therefore, various electronic circuits equipped with this current inverting circuit cannot operate when the voltage is reduced (0.9 to 0.8 V), such as when a panteri is used as a driving power source.

SUMMARY OF THE INVENTION An object of the present invention is to provide a current inverting circuit that can lower the minimum operating voltage and ensure stable operation even if the terminal voltage decreases due to battery exhaustion.

The present invention includes a constant current source that sets a reference current, a first transistor or transistor to which a base current is supplied by the constant current source, a second transistor to which the base current is supplied by this transistor, and a first The third transistor is inserted between the base and emitter of the transistor, and the base current is regulated by the second transistor, and the collector current is regulated by the constant current source.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

FIG. 2 shows an embodiment of the current inversion circuit of the present invention. In the figure, the first transistor 20 is connected to the power supply terminal 2
The emitter is connected to a power supply line from 2 to 2 to which a drive voltage Vcc is applied, and a constant current source 26 is connected between the base and the reference potential point terminal 24. The collector and the collector of the transistor 20 are connected to the base of a second transistor 28, and the emitter of this transistor 28 is connected to a reference potential point. Further, a capacitor 30 is inserted between the base and collector of the transistor 28, and the base of a third transistor 32 is connected to the collector.

Transistor 32 is connected between the base and emitter of transistor 20.

Then, an output transistor 34 is provided whose base and emitter are commonly connected to the transistor 32, and an output terminal 36 is formed at the collector of this transistor 34.

The operation will be explained based on the above configuration. Assuming that the reference constant current given by constant current #26 is I1, based on this current I+, a constant base current is given to transistor 20 & 20, and current 3 flows through transistor 20. This current I3 becomes the base current of the transistor 28, and a current 2 is applied to the collector of the transistor 28 from the base of the transistor 32. This current inversion circuit forms a feedback loop, and in a balanced state, current flows through the transistor 34! + flows and can be taken out from the output terminal 36.

In this case, the capacitor 30 constitutes a phase correction canomer and functions to prevent oscillation.

Here, the current amplification factor β of the transistor 20.28.32
Considering, the relationship between each current 11 and I2.13 is I
3 = I 2 / 102 = I t / L O'
is given by Therefore, the emitter-to-collector voltage of the transistor 20 is 1/β2=1 of the current I+.
/104, which is a small value. That is, VF'
decreases by 24.0 mV from 660mV, and becomes 420
m, V (=660-24.0). Therefore, according to such a current inverting circuit, the operating voltage decreases to 0.
If the voltage is reduced by 86, the operating voltage is reduced to 0.62, and a similar current reversal operation can be obtained at a lower voltage.

In the embodiment shown in FIG. 3, each transistor of the previous embodiment is constructed in the same manner as transistors of opposite conductivity types.

That is, the PNP type first transistor 20 of the above embodiment
is an NPN type transistor 40, the NPN type second transistor 28 is a PNP type transistor 48, and the PNP type third transistor 32 is an NPN type transistor 4.
2. The PNP type output transistor 34 is configured with an NPN type transistor 44, and the constant current source 26
corresponds to the constant current source 46. Other parts that are the same are given the same reference numerals.

According to such a configuration, the transistors 40.42.4
The direction of the base current of 4.48 is opposite to that of the current inversion circuit of the previous embodiment, and the current is sucked into the output terminal 36, and the same effect can be expected.

Further, FIG. 4 shows another embodiment of the current inversion circuit of the present invention, and the same parts as in the embodiment shown in FIG. 2 are given the same reference numerals. In the figure, transistors 20a and 28a and transistors 20b and 28b correspond to the circuit consisting of the first and second transistors 20 and 28 of the previous embodiment, and in this embodiment, they have a two-stage configuration. That is, the transistor 20a has its base connected to the constant current source 26, its collector connected to the base of the transistor 28a, and its emitter connected to the power supply line to which the drive voltage Vcc is applied from the power supply terminal 22. Further, the emitter of the transistor 28a is connected to the reference potential point, the collector thereof is connected to the base of the transistor 20b, and the transistor 28a is connected to the base of the transistor 20b.
b has its emitter connected to the power supply line, and its collector connected to the base of transistor 28b. and,
The collector of the transistor 28b is connected between the base of a transistor 50, which corresponds to the third transistor 32 of the embodiment, and a reference potential point, and the bases of the transistor 50 are commonly connected to the bases of the transistors 320.

The transistor 50 is connected between the power supply line and the reference potential point via a resistor 52 on the collector side, and has an output terminal 54 formed at the collector.

As in this embodiment, the first and second transistors 20
If a, 20b, 28a, and 28b are configured in two stages, the operating voltage can be further lowered, and the number of stages can also be increased.

As explained above, according to the present invention, since the voltage drop inside the circuit is reduced, the minimum operating voltage can be lowered, and, for example, stable operation can be obtained even if the terminal voltage decreases due to battery consumption. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a conventional current inverting circuit, FIG. 2 is a circuit diagram showing an embodiment of the current inverting circuit of the present invention, and FIGS. 3 and 4 are circuit diagrams showing other embodiments of the present invention. It is a diagram. 20.40.20a120b...first transistor, 28.48.28a, 20b...second transistor, 26.46...constant current source, 32.42.50...
-Third transistor. 103 Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A constant current source that sets a reference current, a first transistor to which a base current is supplied by this constant current source, a second transistor to which a base current is supplied by this transistor, and a transistor between the base and emitter of the first transistor. and a third transistor inserted into the constant current source, the base current of which is regulated by the second transistor, and the collector current of which is regulated by the constant current source.