JPS6033717A - Current mirror circuit - Google Patents

Abstract

PURPOSE:To attain low voltage operation by connecting resistor between a base and a collector of a transistor (TR) being a component of a current mirror circuit and supplying an input current to the collector of the said TR. CONSTITUTION:When a current of an input current source IIN is 0, since a current IO flows to the 1st and 2nd TRs Q21, Q22, a voltage drop of R11.IO is produced across a resistor R11. Since a collector-emitter voltage VCE of the Q21 is VBE-R11.IO by the voltage drop, a VCE[Q21] is nearly 0.35V in setting the R11.IO to nearly 0.35V. In adding a current from the input current source IIN next, the operating current of the Q21 is IO+IIN. Further, a current flowing to the Q22 having the common base to the Q21 is also IO+IIN. Since the current flowing to the resistor R11 is IO and no change is caused by the input current IIN, the colector-emitter voltage VCE of the Q21 is constant and the VCE, i.e., the potential of a point A is lowered as low as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to mirror circuits, and particularly to mirror circuits designed to operate at low voltages.

[Technical background of the invention and its problems]

2. Description of the Related Art Conventionally, a current mirror circuit configured as shown in FIG. 1 is known as a current mirror circuit widely used in general electronic equipment including audio equipment.

That is, a constant current output I is output from the collector of a transistor Q2 whose base is commonly connected to a diode-connected transistor Q1 whose collector receives an input current from an input current source IXN. This is to obtain UT.

However, the current mirror circuit shown in FIG.
As shown in FIG. 2, if an attempt is made to drive the differentially connected transistor Qs connected to the input voltage vIN so that Qs=Q<, then the base-emitter voltage VB of the transistor Q1
F, (approximately 0.7V) becomes a hindrance, and the transistor Q4
The problem has been that the current mirror operation cannot be performed because the current is saturated.

Therefore, as shown in Figure 3, the emitter is connected to the input current source I.
Install a constant current source at the connection point between □ and resistor R1 and at the base. Constant current output ■ from the collector of transistor Q12 connected to the connection point between diode Qtt and resistor 1t2. U
A current mirror circuit that obtains T is considered.

The current mirror circuit of FIG. 3 can perform normal current mirror operation when driven in the same relationship as that of FIG. 2 as shown in FIG. 4.

However, in this case, the voltage drop due to resistors R1, R, VC is
Since it is connected in series with □, there is a problem in that it is necessary to operate at a low voltage such that the cc voltage of the power supply □ is 1 V or less.

[Purpose of the invention]

Therefore, this invention has been made in view of the above points, and has been improved so that it is easily possible to operate at a low voltage, such as when the power supply voltage is LV or less, with the simplest possible configuration. The purpose is to provide an extremely good current mirror circuit.

[Summary of the invention]

That is, the current mirror circuit according to the present invention includes first and second transistors whose respective emitters are connected to a reference potential point or a power source and whose respective paces are commonly connected to each other, and of these first and second transistors. A constant current source connected between a common base and a power supply or a reference potential point, and a resistor connected between the base and collector of the transistor i1, and the constant current source and the resistor The transistor is characterized in that the collector potential of the transistor is set lower than the base potential, an input terminal is supplied to the collector of the first transistor, and an output current is derived from the collector of the second transistor. .

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the drawings.

That is, as shown in FIG.
1 has its collector connected to the power supply v via the input current source IIN.
cc, and is connected to its own base via a resistor R11, and its emitter is connected to the reference potential point GND.

Further, the second transistor Q22 has its pace commonly connected to the pace of the first transistor Q21, and is connected to the constant current source I. It is connected to the power supply vCC through the terminal, and its emitter is connected to the reference potential point GND, and its collector is a constant current output terminal. It is designed so that UT can be derived.

In the above configuration, when the current from the input current source 'IN is O, the operation is similar to that of the current mirror circuit shown in FIG. 1, and the first and second transistors Q2
1. A current In will now flow through Q2□. Also, a current ■B (=■o) will flow through the resistor R11, so R11 is connected to both ends of it. A voltage drop occurs.

This makes it the same as the first transistor Q21, so if L11·Io is set to about 0.35 V, vCE (Q21) also becomes about 0.35 V.

Next, when the current from the input terminal source IIN is applied in an increasing direction, the operating current of the first transistor Q21 becomes 1°+'IN.

In addition, the current flowing through the second transistor Q22, which has a common pace with the first transistor Q21, also flows (
).

At this time, the resistor R11 [the flowing current is Therefore, no change occurs due to the input current source ■IN.

In other words, the voltage drop across the resistor gx□ is -, and the voltage drop between the collector and emitter of the first transistor Q21 is vcF.
! is also constant, and the vcIe, that is, as shown in (A)
Since the potential at a point can be lowered, applications as shown in FIG. 6 are possible.

In other words, Figure 6 shows the human-powered No. 3 Hx machine in Figure 5.
and a fourth transistor (4□3#'J24), vIN in the figure is an input voltage source, and I is a constant current source.

By setting the emitter voltage vCE to about 0.35 V, the fourth transistor Q24 has its VC)i, 0.
．． 3SViTff becomes 1 degree, and normal current mirror operation can be performed without saturation.

In this case, the power supply V. , : and the reference potential point GND, the voltage loss is small so that there is no series connection other than the base-emitter voltage vBo of the transistor used and the collector-emitter voltage VcE, voc<0.8
This makes it possible for uJ to operate at as low a voltage as possible.

And constant voltage j4 source■. The current value is V. By setting the current value proportional to VC to an appropriate value, the VC of the first transistor Q2□ can always be 7VBF regardless of temperature changes. Figure 7 shows another embodiment. 5 shows the case where the polarities of the transistors in FIG. 5 are reversed. A compensating mother resistor It, □ is inserted to reduce the influence of the base current, and an output transistor QC5 is inserted to increase the emitter surface area and obtain a current gain.

In this case, each transistor Q21 1Q22 1Q23
Emitter resistor B-13・R14・It 1 inserted in
．． If the ratio of the transistors Q21, Q1121, and Q10 is 1:1:0.5, and the ratio of the emitter surface of each transistor Q21, Q1121, and Q10 is 'tll:2, then the constant current output from each collector of Q, 2, and Q2S is 1 = I, respectively. 10l 01lT1 0 IN ■. , T2= 2 (Io×I, N).

FIG. 8 also shows another embodiment, in which the output type Mt current mirror of the differential pair transistors Q311Q32 is returned by a pair of transistors Q331Q35 and Q341Q36, and the difference current is generated by the transistors Q36 and Q38 to load the load. This is a case where the voltage output is changed by supplying the voltage to the resistor RL.

It goes without saying that the present invention is not limited to the embodiments described above and illustrated, and that various modifications and applications can be made without departing from the scope of the present invention.

〔Effect of the invention〕

Therefore, as described in detail above, according to the present invention, an extremely good current current is improved so as to easily achieve low voltage operation with a power supply voltage of 1 V or less with the simplest possible configuration. A mirror circuit can be provided.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 to 4 are configuration explanatory diagrams showing conventional current mirror circuits, and FIGS. 5 to 8 show one embodiment and other embodiments of the current mirror circuit according to the present invention. FIG. (Jzt+Qzz...transistor, IIN...
・Input terminal source, vcc...power supply, RLl...resistance,
GND: Reference potential point, Io: Constant current source. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 3 Figure 2 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] first and second transistors, each emitter of which is connected to a reference potential point or a power source, and each base of which is commonly connected to each other, and between the common bases of the first and second transistors and the power source or reference potential point; A constant current source connected to the base and a resistor connected between the base and collector of the first transistor are provided, and the collector potential of the first transistor is changed from the base potential by the constant current source and the resistor. 1. A current mirror circuit, characterized in that the current mirror circuit is configured to supply an input current to the collector of the first transistor, and to derive an output current from the collector of the second transistor.