JPH03156513A - Current inverting circuit - Google Patents

Abstract

PURPOSE:To perform the current inverting operation even at the time of reduc ing the voltage of a battery by leading a current from bases of first and second transistors Trs to the pair of Trs in accordance with the current on the collector side of the first Tr to reduce the minimum operating voltage. CONSTITUTION:A feedback loop is formed by a pair of Trs 30a and 30b in a current inverting circuit, and currents flowing to Trs 32 and 28b are balanced, and a constant current I1 is led to a Tr 50 from the side of a line 23 and is taken out from an output terminal 54. When the current amplification factor of Trs 32, 20a, 28a, 20b, and 28b is denmoted as beta, relations between the con stant current I1 and currents I2, I3, I4, and I5 are expressed with I4=I5/beta, I3=I4/beta, I2=I3/beta, and I5=I1/beta<4>. Consequently, the base current flowing to the Tr 20a is 1/beta<4> times as large as the constant current I1, and the voltage between the emitter and the collector of the Tr 20a is considerably reduced. Therefore, the minimum operating voltage of the current inverting circuit is reduced, and the current inverting operation of high reliability is realized with a low operat ing voltage.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a current inverting circuit used as a constant current source in various circuits constituted by integrated circuits.

[Conventional technology]

Conventionally, current reversal circuits used on integrated circuits include:
For example, as shown in Figure 2, a transistor 2 whose base and collector are commonly connected (i.e., diode connected)
The transistor 2 is connected between the power supply terminal 4 and the ground terminal 6 to form a series circuit with a constant current source 8 installed on the base/collector side. The drive voltage Vα applied to the power supply terminal 4 is applied to the emitter side of the transistor 2 through the power supply line 5, and the ground terminal 6 is connected to a ground point as a reference potential point. The bases of transistors 10 are commonly connected to the base and collector of this transistor 2, the emitter of this transistor 10 is connected to the power supply line 5 together with the emitter of transistor 2, and the collector has an output that takes out a constant current as an inverted current. A terminal 12 is formed. Therefore, according to this current inversion circuit, when constant current I is applied as a reference current by constant current source 8, that constant current I flows through transistor 2 as a diode, and the emitter of transistor 2 (anode of the diode) A forward voltage drop vF occurs between the base and collector (cathode of the diode). transistor 100 base
Since the emitter voltage ■□ is regulated by the forward drop voltage V generated in the transistor 2, it is equivalent to inserting a constant current source between the base and emitter of the transistor IO. Moreover, the base current of the transistor 10 is regulated by the constant current source 8, and in an integrated circuit, each transistor 2
．． Since the electrical characteristics such as the current amplification factor of 10 can be set equally with high precision, when a constant current 1 is applied to the transistor 2, the constant current I flows to the transistor 10 and outputs the output terminal 1.
It will be taken out from 2. In such a current inversion circuit, a constant current corresponding to the constant current I flowing through the transistor 2 can be taken out on the transistor 10 side due to the tfL inversion characteristic (current mirror effect) of the transistor 2 and the transistor IO.

[Problem to be solved by the invention]

By the way, in this current inverting circuit, a series circuit of a transistor 2 as a diode and a constant current source 8 is inserted between the power supply line 5 and the reference potential point, and the constant current source 8 is composed of a transistor. In addition to the transistor 2, a transistor forming the constant current source 8 is inserted in series. Therefore, this voltage drop is the forward drop voltage
, and saturation voltages of the transistor of the constant current source 8, ■ and □. Generally, in a monolithic integrated circuit made of silicon, the forward voltage drop ■, is 660 mV, and the forward voltage drop ■, □ is 0.2
2, the combined value is as high as 860 mV, and the minimum operating voltage is required to be about 0.9 V. Therefore, in various electronic circuits equipped with this current reversal circuit, if the power supply voltage drops, such as when a battery is used as the drive power source, the circuit cannot operate at a voltage of 0.9 to 0.8 V. be. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a current inverting circuit that lowers the minimum operating voltage and enables current inverting operation even when the power supply voltage decreases due to battery exhaustion or the like.

[Means to solve the problem]

That is, the current inversion circuit of the present invention includes first and second transistors (32, 50) having a common base, and the first transistor (32) connected in series to the first transistor (32).
a constant current source (26) that provides a reference current to the transistor; and a third transistor (20) that receives a base current from the constant current source and draws current from the power supply line side.
a, 20b), a fourth transistor (28a, 28b) that draws a current corresponding to the base current applied through the third transistor, and the first and second transistors Transistor pair (30
a, 30b).

[For production]

When a base current is applied to the third transistor by the constant current of the constant current source, a current corresponding to the base current is drawn into the third transistor from the power supply line side. The current flowing through the third transistor becomes the base current of the fourth transistor, and the fourth transistor is given a current sinking ability corresponding to the base current. By using a transistor pair consisting of a third and fourth transistor having such a function, current is drawn from the bases of the first and second transistors to the pair of transistors according to the current on the collector side of the first transistor. , 1st
A current mirror effect is obtained in which the constant current flowing through the second transistor can be caused to flow to the second transistor side. In addition, in this current inversion circuit, compared to a conventional current inversion circuit in which the base and collector are coupled, the minimum operating voltage can be lowered by the transistor pair, and when the voltage decreases due to battery depletion, etc. Also, current reversal operation can be obtained.

【Example】

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. FIG. 1 shows an embodiment of the current inversion circuit of the present invention. This current inversion circuit is equipped with first and second transistors 32.50 having a common base, and the emitters of each transistor 3 and 2.50 are connected to a power supply line to which the power supply voltage VCC is applied through the power supply terminal 22. It is connected to the 23 side. A constant current source 26 that causes a reference current 1 to flow through the transistor 32 is connected in series to the collector side of the transistor 32 . A plurality of transistor pairs 30a and 30b are installed that draw base current of the transistor 32.50 according to the current on the collector side of the transistor 32, and the transistor pair 30a includes the third transistor 20a, the fourth transistor 28a, and the transistor The pair 30b consists of a third transistor 20b and a fourth transistor 28b. That is, the base of the transistor 20a is connected to the transistor 32.
The transistor 20a is connected to the collector side of the transistor 20a and is supplied with a constant current 2 by a constant current source 26, and the transistor 20a is connected to the power supply line 2
A current corresponding to the base current is drawn from the emitter side connected to 3. A transistor 2 is connected to the collector of this transistor 20a.
The base of transistor 8a is connected, and the current flowing through transistor 20a becomes the base current of transistor 28a. The emitter of the transistor 28a is grounded, and the base of the next stage transistor 20b is connected to its collector side. The emitter of the transistor 20b is connected to the power supply line 23, and a current corresponding to the base current drawn into the transistor 20a flows from the power supply line 23 side to the transistor 20b. This transistor 20
The base of the transistor 28b is connected to the collector side of the transistor 20b, and the current flowing through the transistor 20b becomes the base current of the transistor 28b. The collector of transistor 28b is connected to the base of transistor 32.50, and its emitter is grounded. A resistor 52 is connected to the collector side of the transistor 50, and an output terminal 54 is formed. The operation will be explained based on the above configuration. Constant current 1+ as a reference current given by constant current source 26
Based on this, a constant base current is applied to the transistor 20a, and a current I2 flows through the transistor 20a from the power supply line 23 side. This current ■2 is the transistor 28
a, and the transistor 28a has a current corresponding to the base current! , is drawn in, and this current I
, becomes the base current of the transistor 20b. Therefore, a current I4 flows through the transistor 20b, and this current I4 flows through the transistor 20b.
4 becomes the base current of the transistor 28b, and a current I is drawn into the transistor 28b from the base of the transistor 32.50 using the current 4 as the base current. This current I, flows from the transistor 20a to the constant current source 26
The current flowing through the transistor 32 and the current Is are balanced. That is, a feedback loop is formed in this current inversion circuit by the transistor pair 30a and 30b, and when the current flowing through the transistor 32 and the transistor 28b are balanced, a constant current 11 is drawn into the transistor 50 from the power supply line 23 side. This will be taken out from the output terminal 54. Here, the transistor 32, the transistors 20a, 28
If the current amplification factors of a, 20b, and 28b are β, then the constant current 11 and the current L,! ! The relationship between , Im, ■ is as follows: 1. =1
．． /β, 1. =1. /β, It=■s/β, Is""I
It becomes I/β4. Therefore, the base current flowing through the transistor 20a is 1/β4 of the constant current 1, and the emitter-collector voltages V and l of the transistor 20a are significantly reduced. Therefore, the minimum operating voltage of the current inverting circuit is lowered, and reliable current inverting operation can be obtained even at a low operating voltage. In the embodiment, a two-stage transistor pair 30a,
30b is installed, however, three or more stages of transistor pairs may be connected in cascade, and if a configuration of three or more stages is used, the minimum operating voltage can be further reduced.

【Effect of the invention】

As explained above, according to the present invention, it is possible to reduce the voltage drop due to the constituent transistors and lower the minimum operating voltage. For example, when a battery or the like is used as a drive power source, the terminal voltage decreases due to its consumption. Stable current reversal operation can be obtained even when the current is reversed.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the current inverting circuit of the present invention, and FIG. 2 is a circuit diagram showing a conventional current inverting circuit. 20a, 20b...Third transistor 26...Constant current source 28a, 28b...Fourth transistor 30a, 30
b...Transistor pair 32...First transistor 50...Second transistor

Claims (1)

[Claims] 1. First and second transistors having a common base; a constant current source connected in series to the first transistor to supply a reference current to the first transistor; With a third transistor that is given a base current by a current source and draws current from the power line side,
a transistor pair comprising a fourth transistor that draws current in accordance with the base current applied through the third transistor, and draws current from the bases of the first and second transistors in accordance with the current flowing through the first transistor; A current reversing circuit characterized by comprising: