JPH0344205A - Current mirror circuit - Google Patents

Abstract

PURPOSE:To set and correct the temperature characteristic of a current ratio of two currents of a current mirror circuit optionally by constituting a resistor connecting between a power supply and an emitter of a transistor(TR) pair forming the current mirror circuit with a non-correction part and a correction part and setting and correcting the resistance ratio of two resistors with the correction part. CONSTITUTION:An emitter of one TR Q1 of TRs Q1, Q2 whose bases are connected in common in a current mirror circuit 11 connects to a power supply Vcc via a 1st resistor R1 and the collector connects to a power supply Vee via a constant current circuit 3. Moreover, the emitter of the other TR Q2 connects to the power supply Vcc via a 2nd resistor R2 and the collector connects to a load circuit 4. Furthermore, the 1st resistor R1 consists of a non- correction part R1-1 and a correction part R1-2 and the 2nd resistor R2 consists of a non-correction part R2-1 and a correction part R2-2. Thus, the temperature characteristic attended with the deviation of the characteristic of the pair TR and the temperature dependency caused in the peripheral circuit are eliminated by adjusting the correction part.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a current mirror circuit.

This makes it possible to set the temperature characteristics particularly in highly accurate circuits with high precision.

2. Description of the Related Art Conventionally, this type of current mirror circuit has had a configuration as shown in FIG. In Figure 6, 1 is a current mirror circuit.
3 is a constant current circuit, and 4 is a load circuit. The current mirror circuit 1 includes a first . A transistor pair Q1 . with a second resistor R1e R2 and a pace connected in common. It consists of Q2. As is well known, in a current mirror circuit, transistor pair Q1. By making Q2 and the two resistors 1-R2 have the same characteristics and the same value, two currents 11.I
2 has the same absolute value and temperature characteristics.If the constant current 11 generated in the constant current circuit 3 had no temperature dependence, the current value given to the load circuit 4 would be 11, and its temperature characteristics would be 0. becomes. However, what are the conditions for achieving the above characteristics with this type of current mirror circuit?

Transistor vs. Q! , the characteristics of Q2 are completely aligned, but in reality, factors that occur in the IC production process and
The slight difference between the two resistors R1 and R2, as well as factors occurring in circuits other than the circuit concerned, inevitably exhibit temperature dependence. This is D/A.

In circuits that perform high-precision calculations, such as computer-to-digital converters and high-precision calculations.

It had major drawbacks such as non-negligible variations in characteristics due to temperature.

Problems that the invention aims to solve The present invention solves these problems.

This makes it possible to create a current mirror circuit with excellent temperature characteristics that is suitable for high-precision circuits, and it also makes it possible to modify the temperature characteristics of the entire circuit, including one periphery.

Means for Solving the Problem In order to solve this problem, the present invention has a structure in which the ratio of two resistances constituting a current mirror circuit is slightly shifted from 1/1.

In this manner, it is possible to eliminate temperature characteristics caused by deviations in characteristics between transistors and temperature dependence occurring in peripheral circuits.

Embodiment FIG. 1 is a diagram showing the configuration of an embodiment of the current mirror circuit of the present invention. Reference numeral 11 denotes a first current mirror circuit, and the bases of the current mirror circuit 11 are connected in common to a pair of transistors Q1. ．． One transistor Q of Q2
The emitter of one transistor q2 is connected to the power supply Vco through the first resistor R1, the collector is connected to the power supply Vco through the constant current circuit 3, and the emitter of the other transistor q2 is connected to the power supply Vco through the second resistor R2. Connected to power supply Vcc.

The collector is connected to a load circuit 4. The first resistor R1 is composed of an unmodified part "1-1" and a modified part R1-2, and the second resistor R2 is composed of an unmodified part R2-1 and a modified part R2-2. .The operation will be explained here.

Two resistors R1*R of the first current mirror circuit 11
Two currents 11 when the ratio R1/R2 of 2 deviates from 1
The temperature characteristics of m "ratio of 2" 2/It are as follows.

II R1+v! +11 =I1 ”2 + v11
12...■ From the above formulas ■, ■, and ■.

I2/I, temperature characteristic 1〒(1,/I, ) =83.5
X1076 above formula ■ is the ratio of two currents "2/It" is 1
When , the temperature characteristic is 0 or (I2 II) is
The polarity of the temperature characteristic is different between positive and negative, and the current ratio I2/1
1, the magnitude of the temperature characteristics also changes. This means that by changing the ratio of resistors R1 and R2 connected between the respective emitters of the transistor pairs of the current mirror circuit and the power supply Tea,
This means that the polarity and magnitude of the temperature characteristic of the current ratio "2/"1 of this circuit can be changed, and in the embodiment of FIG.
one resistor R+ + '2, the unmodified part R+-1+'2-
1 and modification parts R1-2+R2-2, and by cutting the resistance of the modification part with a laser modification machine or the like to change its resistance value, desired temperature characteristics can be obtained.

When setting the temperature characteristics of the current ratio I2/I of the current mirror circuit with high accuracy by shifting the ratio R1/R2 of the two resistors, one way to shift the resistance ratio R1/R2 is to set the first resistor R1 and the second resistor There are two methods of modifying both resistances R2 and a method of modifying only one of them.

One of the above methods is selected depending on the polarity and magnitude required for adjusting the temperature characteristics of the current ratio Iz/I+4.
In this way, the current ratio of the current mirror circuit is 12/I
By accurately setting the temperature characteristics of the transistors Q, , Q2, the current given to the load circuit 4 can be controlled by setting the temperature characteristics of the constant current circuit 3, . All temperature-dependent characteristics occurring in other peripheral circuits can be corrected to have extremely low temperature dependence.

In the case of the embodiment shown in FIG. 1, it has been explained that the temperature characteristic is approximately 0, but since the current ratio I2/11 is shifted from 1, the current factor 2 given to the load circuit 4 is the base current It is different from I. Depending on the load circuit, I,
:I2 is desired, and an embodiment that achieves this is shown in FIG.

The embodiment shown in FIG. 2 is an example in which the load circuit section is composed of a second current mirror circuit, and the transistor pair Q, , Q2
and a first current mirror circuit 1 consisting of resistors R1 and R2.
1. It is composed of a second current mirror circuit 12 consisting of a transistor pair Qs, Qa and resistors R5, R4, and a constant current circuit 3, and the output current of the first current mirror circuit 1 is connected to the base of the second current mirror circuit 12. One transistor Q3 of the transistor pair Q3, Q4 connected to
The emitter of the transistor Q, which is connected to the collector of
The lid is connected to the power supply Vee via a third resistor R5,
The emitter of the other transistor Q4 is connected to the power supply Tea through the fourth resistor R4, and the emitter of the first current mirror circuit 11 is connected to the power source Tea. Second resistance ratio R1/R2 (=)
Correspondingly, the value of the third resistor is set to be 1/k of the value when R1/R2=1.

The operation will be explained below.

I, XR, :I, XR2... ■Here, if the current ratio is I, /I, :R, /R2:.

I, == I2 from I, XR5=I2XR,'=kXI,XR,' ・
If the third resistor R,° is selected such that -=...■, then the collector current l0ut of the transistor Q4 is equal to the first current mirror current l0ut of the first current mirror circuit 11. Second resistance ratio R/R1
It becomes equal to the time of .

Here, from formula ■.

R' = rxR,...■, and the value of the third resistor is 1 of the value when R, /R2 = 1.
/k.

In a highly accurate current mirror circuit, the influence of the base currents of the diode-connected transistors Ch and Qs in the transistor pair cannot be ignored.

Fig. 3 shows an attempt to correct the base current of such a transistor, and transistors Q and l correct the base current of transistor Q.

Transistor Q5° corrects the pace current of transistor Q5.

Such pace current correction is done with semiconductor circuits.

Since this is commonly practiced, the explanation will be omitted.

FIG. 4 shows a third embodiment of the present invention.

This is an example of configuring a D/A and MU/D converter circuit that particularly requires high precision characteristics.

In the embodiment shown in FIG. 4, a transistor Qp is paired with the transistor Q in the first current mirror circuit 11, and a resistor Rp is additionally connected between the emitter of the transistor Qp and the power supply Voc. A plurality of transistors Q5, which are paired with the transistor Q3 of the mirror circuit 2. Q
6. ...and the plurality of transistors Qs-
Q6.・・・・・・Resistors R5, R6, ・・・・・・ are additionally connected between each emitter and the power supply Vee, and the output type fiIbpo from the collector of the transistor Qp and all that are paired with the transistor Q-s are connected. Add the output currents of the transistors! It is configured so that the optical output is I out.

That is, in the embodiment shown in FIG. 4, the first embodiment shown in FIG.
In the second current mirror circuit, another transistor Qp is paired with the transistor Q1, and a plurality of transistors Qs, Qb are paired with the transistor Qs.
,... are additionally connected. In the embodiment of FIG. 4, the transistor Q of the second current mirror circuit 2,
A plurality of transistors p Qa + Q5 + paired with
Q6. Each emitter and power supply Ve
Resistors Qa, Qs, Qb connected between e...
The value of ... is 1.2, 4.・・・・・・It is important to weight each collector'wL style I MSB.
, Ib1t 2 .

I bit a, ---・= is 2 mm, 111 mm,
These transistors Qa, Q5 . . . have a weighted value of 0.5 ml... The collector output currents of Qb... are added to form the current output Iout.

On the other hand, the transistor Q of the first current mirror circuit 11
The current Ibpo from p is connected to the current output point Iout and is used to operate the D/A and mu/D converters in the pie-hole mode. Also in the embodiment shown in FIG. 4, the setting of the ratio R1/R2 of the two resistors R1 and R2 of the first current mirror circuit 11, and the current ratio I
The temperature characteristics of 2/11 can be set arbitrarily, making it possible to configure D/A and MU/D converters with extremely excellent temperature characteristics.

The current mirror circuit shown in Fig. 4 is actually used as a D/A.
To operate as a system/D converter.

Each transistor Q4 of the second current mirror circuit 12. Q5. Q6. It is necessary to add a switch circuit to the current output section of ......, but generally D/A,
This is implemented in a system/D converter, so the explanation will be omitted.

The embodiment shown in FIG. 6 has a built-in D/A converter that operates the current mirror circuit of the present invention as a weighted current generating circuit, and a comparator 6 and a successive approximation register 7 are connected to this, and a successive approximation type resistor 7 is connected to the D/A converter. /D converter. Also in the case of this MU/D converter, it is possible to realize extremely excellent temperature characteristics.

Effects of the Invention As described above, according to the present invention, the resistor connected between each emitter of a transistor pair forming a current mirror circuit and a power supply is composed of an unmodified part and a modified part;
Just as it is possible to arbitrarily set and modify the resistance ratio of the two resistors using the correction section described above, it is also possible to arbitrarily set and modify the temperature characteristics of the current ratio of the two currents in the current mirror circuit. A circuit configuration with highly accurate temperature characteristics becomes possible.

[Brief explanation of drawings]

Figures 1 to 4 are circuit diagrams showing embodiments of the present invention, and Figure 6 is a circuit diagram using the current mirror circuit of the present invention.
The converter circuit diagram, FIG. 6, is a circuit diagram of a conventional current mirror circuit. 11.12...Current mirror circuit, 3...
...Constant current circuit, 4...Load circuit, 6...
...D/A converter, Q, -Q2, Qs, Q
4. Q, '-Qs°, Qp...transistor,
R1...First resistor, R2...Second resistor, R5...Third resistor, R4...
Fourth resistance. R 1-1 step 2-1 ...... Uncensored part. R1-2-R2J...Repair part.

Claims (5)

[Claims] (1) Out of a pair of transistors whose bases are commonly connected, the emitter of one transistor is connected to the power supply through the first resistor, the collector is connected to the power supply through the constant current circuit, and the emitter of the other transistor is connected to the power supply through the constant current circuit. is connected to a power source via a second resistor, and its collector is connected to a load circuit, and the first resistor and second resistor are comprised of an unmodified part and a modified part. . (2) The current according to claim 1, wherein the resistance ratio is changed by modifying both or one of the first resistor and the second resistor, and the temperature characteristics of the current applied to the load circuit are modified. mirror circuit. (3) Transistor pair Q_1, Q_2 and resistors R_1, R
It consists of a first current mirror circuit consisting of a transistor pair Q_3 and Q_4 and a resistor R_3 and R_4, and a constant current circuit. A pair of transistors Q_3, Q connected in common
input to the collector of one transistor Q_3 of _4,
The emitter of the transistor Q_3 is connected to the power supply Vee through the third resistor R_3, and the emitter of the other transistor Q_4 is connected to the power supply V through the fourth resistor R_4.
ee, and the value of the third resistor is set to 1/1 of the value when R_1/R_2=1, corresponding to the first and second resistance ratio R_1/R_2 (=k) of the first current mirror circuit. 2. The current mirror circuit according to claim 1, wherein the current mirror circuit is configured such that k. (4) Transistor Q_p paired with transistor Q_1 and this transistor Q in the first current mirror circuit
A resistor R_p is connected between the emitter of _p and the power supply Vcc, and a resistor is connected between the emitters of the plurality of transistors paired with the transistor Q_3 of the second current mirror circuit and the plurality of transistors and the power supply Vee. Claim 3, wherein the output current from the collector of the transistor Q_p and the output current of all the transistors paired with the transistor Q_3 are added to form a current output.
The current mirror circuit described. (5) A D/A conversion circuit that operates the current mirror circuit according to claim 4 as a weighting current generation circuit.