JPS592412A - Current mirror circuit - Google Patents

Abstract

PURPOSE:To decrease the error of mirror ratio, by the constitution provided with a multi-emitter transistor(TR). CONSTITUTION:The multi-emitter transistor TRM is turned on by flowing a base current from a current source 1, and then a base current flows to TRs TR1- TR6, which are turned on. In selecting a currnt amplification factor hfe of the TRM to a large value in this case, an input current I1 does not flow to the base of the TRs TR1-TR6, and the ratio of the input current I1 and output currents I2, I3, that is, the mirror ratio is kept surely. Since the emitter-collector voltage of the output TR3 is kept smaller with the TR6, the error of the mirror ratio due to the early voltage of the output TR3 is kept smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current mirror circuit used in a current coupling circuit in an electronic circuit.

A conventional general current mirror circuit is constructed as shown in FIG. In the circuit shown in FIG. 1, the ratio between the current 11 flowing through the input measuring current source 1 and the current flowing through the output load 2, that is, the current mirror ratio, is expressed as Iz/I+. At this time, the current engineer 2 connects the transistor Tr1. When transistors with the same characteristics are used for Trz, the following equation is obtained.

h=I+ (Pace current of output side transistor Tr2)×2 Therefore, the difference between the currents I+ and It is the pace current (IB
), the current mirror ratio is not equal to 1. A current mirror circuit having the configuration shown in FIG. 2 has improved this problem. In the circuit shown in Fig. 2, when transistors with the same characteristics are used, the difference between the current 11 flowing through the input measurement current source 1 and the current 2 flowing through the output side load 2 is 2/hfe (where h(6; current The error in the mirror ratio is improved compared to the current mirror circuit shown in Figure 1 because of the amplification factor), but the error in the collector current due to the early voltage of the output transistor (V (J/V)
Ib (however, vA; early voltage of output transistor +
There was a drawback that VCIL (voltage between the emitter and collector of the output transistor) was large. Furthermore, the conventional current mirror circuit shown in Figure 3 is compensated for pace current and early voltage in order to improve mirror ratio errors, but it only has one current mirror output. There were drawbacks.

The present invention provides a current mirror circuit having an input transistor and N output transistors whose bases are connected to each other, in which the emitter of a first transistor is connected to the collector of the input transistor, and each of the N output transistors is connected to the collector of the input transistor. The emitters of the N transistors are connected to the collectors of the transistors, and the emitters of the N transistors are connected at the connection point of the first and N transistors at the connection point of g1, and the input transistor's pace and the N output transistor's bases are connected to each other. are connected at the second connection point, and the first . between the second connection point and the collector of the first transistor;
Pace current of transistors.

In addition, by configuring a configuration in which a multi-emitter transistor that flows a pace current between the input side and the N output side transistors is connected with a diode sandwiched between the second connection point, a multi-output mirror can be formed. The present invention provides a current mirror circuit that can reduce ratio errors.

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 4 is a circuit diagram showing one embodiment of the present invention. Input side transistor Tr1 + output side transistor Tr2
, Tra, and a transistor Tr connected to the collector of each of the input side transistor and the output side transistor.
4 + Trs + Trs and Tr4 + Tr5
.

a multi-emitter transistor Try that supplies pace current to Trs and Trx + Tr2+ Tra;
One emitter of Tru and transistor Tri + T
Diode D connected between r2 + Tr3
i, and resistors R+, R2, connected to the respective emitters of the transistors Trx, Trz, and Tra.
It constitutes a two-output current mirror circuit including Rs.

The transistor Try is a transistor for compensating for errors in mirror ratio due to pace current. Input current factor 1 and output current factor 2 when the characteristics of each transistor are the same
The difference is as shown in the following formula.

Therefore, the error in mirror ratio due to pace current is improved. Transistors Trx, Trz, and Tra supply input current and output current, respectively. Transistor Trs + Trs is transistor Trz, Tra
The emitter-collector voltage is reduced to reduce the influence of the Early voltage on mirror ratio errors. The transistor Tr4b and the diode Di prevent the transistors Tr1+Trz and Trs from becoming saturated. Resistors R+, R2, Rs are transistors T
r1. The influence of the error in the mirror ratio of the current mirror caused by the VB (D variation) of Trz + Tra is reduced.

In FIG. 4, the transistor TrM is turned on by the current flowing through the current source 1, and by turning on the transistor TrM, the transistor Trt + Trz.

Pace current also flows through Tr3+ Tra, Trs, and Trs, and they are turned on. At this time, the transistor Try
If hfe of is selected to be large, the input current ■1 becomes
It does not flow into the pace of Trs + Tre, input current 1 and output current I2.

The ratio of Is, that is, the mirror ratio, can be maintained reliably.

Further, since the emitter-collector voltage of the output transistor Tr3 is kept small by the transistor Tr6, the error in the mirror ratio due to the early voltage of the output transistor is kept small.

FIG. 5 is a circuit diagram of a second embodiment of the current mirror of the present invention. In this figure, the same components as in FIG. 4 are given the same reference numerals. In this second embodiment, 2N transistors Tr21 + "'
”' HTr2N HTr51 * ”'”' +
A current mirror having N outputs is configured by connecting Tr5N. The operation and configuration are the same as in the first embodiment.

In the above embodiment, the transistor used is [-NPN
Although a type transistor is used in this embodiment, it is of course possible to obtain the same effect by using a PNP type transistor.

As explained above, in a current mirror circuit having N transistors on the input side and N output transistors whose bases are connected to each other, the emitter of the first transistor is connected to the collector of the transistor on the input side, and the emitter of the first transistor is connected to the collector of the transistor on the input side. The emitters of the N transistors are connected to the respective collectors of the output transistors of the transistors, and the bases of the first and N transistors are connected at a first connection point, and the base of the input transistor and the The bases of the N output side transistors are connected at a second connection point, and the first... Base current of the first and N transistors between a second connection point and the collector of the first transistor.

and a multi-emitter transistor through which base currents of the input side and N output side transistors flow,
By inserting a diode at the second connection point, a current mirror circuit with multiple outputs and a small mirror ratio error can be realized, depending on the connections.

[Brief explanation of drawings]

1, 2, and 3 are diagrams showing conventional current mirror circuits, FIG. 4 is a circuit diagram showing an embodiment of the power 1/current mirror circuit of the present invention, and FIG. 5 is a circuit diagram showing an embodiment of the power 1/current mirror circuit of the present invention. FIG. 7 is a circuit diagram showing another example of the current mirror circuit. Trl...input side transistor, Tr2'rr31'l'r21~Tr2N-output side transistor, TrM...multi-emitter transistor,
Tr4. Trs+Tr6+Trst ~TrsN-=
fin register, R+, R2, R3, Rt+ -
R2H-resistance, Di...diode, 1...
Constant current source, 2~N+1...Load. Agent Patent Attorney Toshiyoshi Somekawa Figure 1 Ve Figure 2 Figure 3 Figure 4-Vs Figure 5 VB

Claims (1)

[Claims] In a current mirror circuit having input and N output transistors connected to each other, the emitter of the first transistor is connected to the collector of the input transistor, and the N transistor is connected to the collector of each of the N output transistors. The emitters of N transistors are connected to each other, and the first and N transistors are connected to each other.
, and the base of the input transistor and the base of the N output transistors are connected at a second connection point, and the first . a multi-emitter transistor that causes base currents of the first and N transistors and pace currents of the input side and N output side transistors to flow between a second connection point and the collector of the first transistor; A current mirror circuit comprising: a diode connected to the second connection point.