JPS6080307A - Current inverting circuit - Google Patents

Abstract

PURPOSE:To improve the power supply voltage margin on the circuit constitution by constituting a titled circuit so that a transistor (TR) detecting a difference current between a reference constant current and an input current to be applied with current inversion is controlled. CONSTITUTION:A current Ic of a reference constant current source 26 flows to a TR32 by current mirror effect of TRs 28, 32. The current Ic flows similarly to TRs 38, 40 by the current mirror effect of the TRs 34, 38 and 40. When a current Ii drawn out externally flows from an input terminal 42, a difference current (Ic-Ii) flows to a base of a TR46 of a difference current detecting circuit 43, a current proportional to the current difference flows from the emitter of a TR46 to resistors 48, 36 and the emitter potential of the TR32 is increased. Thus, a current proportional to the Ii flows to the TR32 at the balancing state and a current proportional to the Ii is flowed out from an output terminal 44 by said current mirror effect.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current inverting circuit, and particularly to reducing the driving voltage thereof.

2. Description of the Related Art Conventionally, current inverting circuits have been used as constant current sources in semiconductor integrated circuits and the like, and those having the configuration shown in FIG. 1 or 2 have been used. The current inverting circuit shown in FIG. 1 has a diode 4 connected in the forward direction between the base and emitter of a transistor 2, a power supply voltage Vcc applied from a power supply terminal 6 to the anode of the diode 4 and the emitter of the transistor 2, and an input terminal The current drawn from the transistor 8 is inverted and taken out from the output terminal 10 formed at the collector of the transistor 2.

In the current inverting circuit shown in FIG. 2, the base and emitter of the pair of transistors 12 and 14 are made common, and the base and collector of the transistor 12 are short-circuited between the emitter and base of the transistor 16. A power supply voltage ■cC is applied from the power supply terminal 18 to the emitter of the transistor 14, an input terminal 20 is applied to the collector of the transistor 12, and an output terminal 2 is applied to the collector of the transistor 14.
2, and the collector of the transistor 16 is connected to a reference potential point.

In the former current inversion circuit, a forward voltage drop vF across the diode 4 occurs between the power supply terminal 6 and the reference potential point, and in the latter current inversion circuit, a forward voltage drop vF occurs between the base and emitter of the transistors 12 and 14. A voltage drop of 2 VF is generated from the forward voltage drop (IV) of the transistor 16. Therefore, it is not suitable when there is no voltage margin due to the circuit configuration.

An object of the present invention is to provide a current inversion circuit in which the voltage drop is reduced to a value lower than the forward voltage drop between the base and emitter of a transistor.

The present invention includes a difference current detection circuit that detects a difference current between a reference constant current and an input current to be inverted, and a first transistor whose current value is adjusted by feeding back the difference current from the difference current detection circuit. and a second transistor that inverts and extracts a current having the same value as the input current flowing through the first transistor.

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

FIG. 3 shows an embodiment of the current inversion circuit of the present invention. In the figure, a constant current source 26, a transistor 28 whose base and collector are short-circuited, and a resistor 30 are connected between the power supply line where the power supply terminal 24 is formed and the reference potential point. A constant current source 26 sets a reference current, and a first transistor 3 is connected to the base and collector of the transistor 28.
The two bases are connected in common. That is, power terminal 2
Power supply voltage Vcc is applied to transistor 4, and the reference current flowing through transistor 28 is reversed and flows through transistor 32. A transistor 34 whose base and collector are connected in common is connected between the collector of this transistor 32 and the power supply line, with its emitter facing the power supply line, and the emitter of the transistor 32 is connected to a reference potential point via a resistor 36. ing.

The bases of the input side transistor 38 and the second transistor 40 are commonly connected to the base and collector of the transistor 34, and the bases of the transistors 38 and 40 are biased with the forward drop voltage VF between the emitter and base of the transistor 34. is given. transistor 3B,
The emitter of the transistor 40 is connected to a power supply line, the collector of the transistor 38 is formed with an input terminal 42, and the collector of the transistor 40 is formed with an output terminal 44.

A difference current detection circuit 43 is installed to detect a difference current between the input current flowing to the collector of the transistor 38 and the reference current flowing to the transistor 32. That is, the base of a transistor 46 is connected to the collector of the transistor 38 via an equivalent power supply 45, and this transistor 46 is connected to the power supply line and the emitter side of the transistors 3 and 2 with a resistor 48 interposed therebetween.

The operation will be explained based on the above configuration. It is assumed that the current drawn from the input terminal 42 to the outside is Ii, and the current set by the constant current source 26 is [c (>Ii). A current (c flows through the transistor 32 due to the current mirror effect of the transistors 28 and 32. This current 1c also flows to the transistors 3B and 40 due to the current mirror effect of the transistors 34, 38, and 40. However, in this case , the current Ii is drawn from the input terminal 42, so a difference current (lc-1i) between the current Tc and +1 flows into the base of the transistor 46, and a corresponding current (hFE(rc-14)) flows into the emitter of the transistor 46. and flows into the resistor 48.36. However, hFE is the DC current amplification factor of the transistor 46. As a result, the current corresponding to the difference current (Ic-Ii) is converted to voltage and is applied to the emitter and ivy side of the transistor 32. As a result, the emitter potential of the transistor 32 increases according to the difference current (Ic-Ii). Therefore, the collector current of the transistor 32 decreases, and in an equilibrium state, the transistor 32 has an input current 1i. Since a proportional current flows, a current proportional to the current ii flows through the transistor 34 due to the current mirror effect of the transistors 34 and 40, and a current proportional to the current It flows out from the output terminal 44. That is, from the input terminal 42 Current drawn 1
1 can be taken out from the output terminal 44 with the current reversed.

With this configuration, as a result of current control, the voltage drop can be suppressed to a value lower than the forward voltage drop of the diode, enabling low voltage operation and proper current reversal operation even when there is no voltage margin. can be ensured.

FIG. 4 shows another embodiment of the present invention, in which the same parts as the current inverting circuit of FIG. 3 are given the same reference numerals. In the current inversion circuit of this embodiment, except for the transistor 34 of the current inversion circuit shown in FIG. 3, the collectors of the transistors 32 and 32 are commonly connected to the bases of transistors 38 and 40. In this circuit, the transistor 32 draws the base current of the transistors 38 and 40, and the same effect as in the previous embodiment can be expected.

FIG. 5 shows an application example of the current inversion circuit of the present invention, and the third
The same parts as those of the current inversion circuit shown in the figure are given the same reference numerals. That is, a pair of transistors 62 and 64 having a common emitter and a constant current source 66 constitute a differential amplifier, and an input terminal 70 is formed at the base of the transistor 62 via a capacitor 68, and a signal to be amplified is applied. At the same time, a constant bias is applied from the power supply line through the resistor 72, and the base of the transistor 64 is directly connected to the power supply line. Further, the collector of the transistor 62 is directly connected to the power supply line, and the collector of the transistor 64 is connected to the input terminal 42 of the current inverting circuit in order to take out the amplified output via the current inverting circuit. In this case, a constant current source 26 is connected between the base of the transistor 32 and the power supply line, and a bias circuit 76 consisting of a diode 73 and a resistor 74 is connected between the base of the transistor 32 and the reference potential point. given a certain bias. In this embodiment, a resistor 50 is connected between the base of the transistor 46 and the collector of the transistor 38 as an equivalent power supply for DC level shifting in the previous embodiment.
Insert.

With this configuration, the current output of the differential amplifier can be inverted and taken out from the output terminal 44, and the voltage drop in the output can be reduced, making it suitable for various electronic devices that do not have a voltage margin. It is suitable.

As explained above, according to the present invention, it is possible to reduce the voltage drop to a value lower than the forward voltage drop between the base and emitter of the transistor, and to ensure stable current reversal operation even when there is no voltage margin. can.

[Brief explanation of drawings]

FIGS. 1 and 2 are circuit diagrams showing conventional current inversion circuits,
FIG. 3 is a circuit diagram showing an embodiment of the current inverting circuit of the present invention, FIG. 4 is a circuit diagram showing another embodiment of the current inverting circuit of the present invention, and FIG. 5 is a circuit diagram showing an example of application of the present invention. It is a diagram. 32... First transistor, 40... Second transistor, 43... Differential current detection circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 4

Claims (1)

[Claims] A difference current detection circuit that detects a difference current between a reference constant current and an input current to be inverted; a first transistor whose current value is adjusted by feeding back the difference current from this difference current detection circuit; 1. A current inverting circuit comprising a second transistor that inverts and extracts a current having the same value as the input current flowing through the first transistor.