JPS5897911A - Current mirror circuit - Google Patents

Abstract

PURPOSE:To obtain a circuit which operates at a low voltage by providing the 1st transistor (TR) supplied with a reference current from the collector side and the 2nd TR whose base is connected to said TR, and further providing the 3rd and the 4th TRs which are complementary to said TRs. CONSTITUTION:The base and collector of a TR1 are connected in common to a reference current input terminal X, and its emitter is connected a plus-side feeding line Ba through a resistance (R) 6. The base of a TR2 is connected to the base of the TR1; the emitter is connected to the line Ba through an R7, and the collector is connected to the base of an NPNTR8. The emitter of a TR9 is connected to the emitter of the TR2, the base of the TR9 is connected to the collector of the TR8, and the collector is connected to a current output terminal Y1. The bases of TRs 10 and 11 are connected to the base of the TR9, the emitters of the TRs 10 and 11 are connected to the line Ba through Rs 12 and 13, and the collectors are connected to current outout terminals Y2 and Y3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a current mirror circuit that operates stably even with extremely low power supply voltage.

FIG. 1 is a wiring diagram of a conventionally well-known current mirror circuit. In the figure, base 4 current is supplied from the collector side of transistor 1 through input terminal X, and from the collectors of transistors 2, 3.4, output terminals Y1. Y2. It is configured to take out an output current proportional to the reference current via Y3.

By the way, in FIG. 1, the transistor 6 is used for the purpose of improving the matching of input current and output current as much as possible. For example, if the transistor 6 is not used, the most common current mirror circuit can be constructed by connecting the base and collector of the transistor 1, but in that case, most of the reference input current is from the transistors 1 and 2. , 3.4. For example, if the DC current amplification factor of each transistor is 10, a reference current of 100 μA is applied and the base current is 100 μA from each output terminal.
Even if you try to take out the output current to the
Moreover, the ratio of input current to output current depends on the direct current amplification factor of each transistor, so the transistor 5 is indispensable in current mirror circuits that require precision.

However, by using the transistor 6,
There is a problem in that the lower limit value of the power supply voltage applied to the positive power supply terminal B increases.

For example, if the base and collector of transistor 1 are connected, it will operate satisfactorily even if the power supply voltage is 1V or less, but if transistor 6 is used, the power supply voltage will be 1.4V.
If the voltage becomes too low, the base currents of transistor 6 and transistor 1 will stop flowing, causing the problem that they will no longer operate.

In addition to the circuit shown in Figure 1, there is a famous Wilson type current mirror circuit as a current mirror circuit that improves the matching of input current and output current. It required more than double and had the same problem.

The current mirror circuit of the present invention solves the above problems.

FIG. 2 is a circuit connection diagram of a current mirror circuit according to an embodiment of the present invention. In Figure 2, transistor 1
The base and collector of are connected to each other, the collector is connected to the reference current input terminal X, and the emitter is connected to the plus side feed line Ba via a resistor 6. The base of the transistor 2 is connected to the base of the transistor 1,
The emitter of the transistor 2 is connected to a positive power supply line Ba through a resistor 7, and the collector thereof is connected to the base of an NPN transistor 8 complementary to the transistors 1 and 2.

Further, the emitter of the transistor 2 is connected to the emitter of a transistor 9, the base of the transistor 9 is connected to the collector of the transistor 8, and the collector is connected to the first current output terminal Y1. The base of the transistor 9 is connected to the bases of the transistor 1o and the transistor 11, the emitters of the transistor 10.11 are connected to the positive feed line Ba through the resistor 12.13, and the base of the transistor 0.11 is connected to the base of the transistor 10.11. Each collector has a second. Third current output terminal Y2. Connected to Y3.

Note that the emitter of the transistor 8 is connected to the negative power supply line C&.

Now, in the circuit shown in Figure 2, the resistance is 6.7°12.13
The resistance values of transistors 2, 8, 9, and 10.11 are respectively R61R71R121R13, and the DC current amplification factors are β1. β2. β8. β9゜β10'
β1. And the base-emitter voltage is vBEl, respectively.
l BE2+vBE81vBE91vBE101vB
E11■, the collector current is I4. I,, I8. I9
, 11°.

I11, the reference current l drawn from the reference current input terminal X, and the 1st. Second. Third current output terminal Y1. Y2. Output current IA1 flowing out from Y3
．． Ia2. ! a. (It is assumed that a load is connected to each output terminal.) The relationship is as follows! 2β8 = 18
・・・°・°・・・・・・°・River・
・°・Pa・′kawa... (3) (3) From equation (4), (1) # (2) t (7), From equation (10),... ·············song(
11) (1) , (2) , (5) , (8)
, Equation (10)...
・・・・・・・・・－・・・(12)(1),(2)
, (5) j (9) l From equation (10), 16.1
0161901.・1.・・・・・・・・(13) Here, β2. β8. β9. β1°, β1. are both 10
, and the emitter areas of transistors 9, 10, and 11 are set so that their emitter current densities are approximately equal. In Fig. 2, the emitter current density of transistor 2 is the same as that of transistor 1. By doing so, the equations (14) to (1,8) can be made equivalent to vBE and vBE2. By connecting a resistor between the pace and emitter of transistor 80 as shown in Figure 3, or by drawing part of the collector current of transistor 2 through another constant current circuit as shown in Figure 4, the difference between vBEl and vBE2 can be changed. The difference can be made zero, and it is also possible by making the emitter areas of transistor 1 and transistor 2 different.

Now, to simplify the explanation, let us assume that vBE, =vBE2 holds, then R6=R7=R42=R13
Set to β9. Assuming that both β1° and β11 are 1o, in the case of light, I! is 1ooμA, the output current Ia1. Ia2. air. are 90 μA in each case, compared to the case where the base and collector of transistor 1 in Fig. 1 are shorted (as mentioned earlier, in that case, it is 100 μA).
The output current is 70 μA for an input current of μA. )
, the matching has improved.

Furthermore, as is clear from equation (14) +, (16) l (16), in the current mirror circuit of the present invention, the resistor 7
, 12°13 is set to a fraction of the resistance value of resistor 6, and the output current is made to be several times the input current or more, the input reference current l! There is no problem in matching the output current to the current.

This is because the base current required for transistors 9, 10, 11 is not supplied directly from the input reference current, but via transistor 8.

Now, in the circuit of FIG. 2, for example, there is a
Even if a voltage drop of 0.00 mV is caused, the voltage between the base and emitter of the transistor 90 is about 0.66 V,
Since the saturation voltage of transistor 8 is 0.2V or less,
It operates satisfactorily even when the power supply voltage is lower than 1V.

In addition, although three current output terminals are provided in FIG. 2, these can be added as needed, or the transistors 10 and 11 degrees and the resistors 12 and 13 can be omitted. It is also possible to provide multiple current output terminals.

FIG. 3 shows another embodiment of the present invention, in which the structures of transistors 1 and 1o are set so that the emitter current densities of transistors 2 and 9 are approximately the same.

That is, in equation (12), vBEl-vBE2=vBE10-vBE9 """
Since “”””’(”) holds true, vBEl and vBE2
This eliminates mismatching caused by the voltage difference.

Furthermore, although the circuit shown in FIG. 3 has long used the collector current of the transistor 9 as the output current, it can also be taken out as the output current if necessary.

FIG. 4 is also a circuit wiring diagram showing another embodiment of the present invention.
The emitter areas of the current output transistors 10, 11, and 14 are set to a ratio of 3:2:2, and the output terminals Y2. Y3. Y
The current value that can be taken out from the transistor 4 is determined, and furthermore, the transistor 15 is configured to draw a current half the collector current of the transistor 9 from the collector of the transistor 2. Further, it is configured so that a current approximately one-third of the reference current is taken out from the collector of the transistor 16 whose pace is connected to the pace of the transistor 1 via the output terminal Y0.

By the way, the embodiments of the present invention shown in FIGS. 2, 3, and 4 all operate even when the current voltage is lower than 1V, but the scope of application of the present invention is not necessarily limited to this. The present invention is not limited to current mirror circuits that operate under a power supply voltage of 1 V or less, but the matching accuracy can be further improved by applying the present invention to the conventional current mirror circuit shown in Fig. 1. I can do it. -For example, the current mirror circuit of the present invention can be applied when supplying accurate constant current output to many output terminals based on a minute reference current, as is often seen in D-A converters. This makes it possible to achieve extremely high matching accuracy.

FIG. 6 shows a 10-bit D as yet another embodiment of the present invention.
- This shows an example of the configuration of a current mirror circuit for an A converter, as already explained.

Emitter current density of transistor 1 and transistor 10
, 11.17, 18, 19, 20, 21.

Set the emitter current densities of 22, 23, and 24 to be the same, and further set the emitter current density of transistor 2 and
By setting the emitter current densities of transistor 9 to be the same, the difference in voltage between the pace and emitter of each transistor can be made zero, and the pace current of transistor 1 and transistor 2 is set to be the same as that of transistor 6. and transistors 9-1
Since the base current of 1°17 to 24 is supplied by transistor 8, most of the reference input current is supplied to the collector of transistor 1, and output current with very good matching accuracy is taken out from output terminals Y2 to Y11. I can do it.

In the embodiments of the present invention shown in FIGS. 2 to 5, PNP transistors are used as output transistors, but these are all replaced with NPN transistors, and transistors 8, 16, etc. are replaced with PNP transistors. , )
It goes without saying that the same effect can be expected even if replaced with a transistor.

To summarize the above, the present invention can be applied from the collector side to the input terminal (
A reference current is supplied through the reference current (corresponding to a second transistor (corresponding to No. 2) whose emitter is connected to the feed line through a resistor (corresponding to No. 7), and a second transistor (corresponding to No. 2), which is complementary to the first and second transistors, a third transistor (corresponding to No. 8) whose current is supplied from the collector of the second transistor, whose emitter is connected to the emitter of the second transistor and whose base current is supplied from the collector of the third transistor; The fourth transistor to be
(equivalent to), and in the embodiment, further.

a fifth transistor (corresponding to 1o) whose base is connected to the base of the fourth transistor and whose emitter is connected to the feed line; and a fifth transistor whose base is connected to the base of the fourth transistor, The device includes a sixth transistor (corresponding to No. 11) whose emitter is connected to the power supply line, and seventh to fourteenth transistors having a similar configuration.

Further, in the embodiment of FIG. 2, the fourth. 6th. Although the configuration is such that the output current is taken out from the collector of the sixth transistor, in the embodiment shown in FIG. 3, the configuration is such that power is supplied to the collector of the fourth transistor from the negative power supply line Ca.

In this manner, the current mirror circuit of the present invention supplies the collector current of the second transistor to the base of the complementary third transistor, and supplies the collector current of the third transistor as the base current of at least the fourth transistor. This structure not only improves matching accuracy even with extremely low power supply voltages, but also enables high-precision matching even when used with relatively high power supply voltages. It has great effects, such as being able to obtain a large amount of output current based on a small reference current while maintaining the standard current.

[Brief explanation of the drawing]

FIG. 1 is a circuit connection diagram showing a conventional example, and FIGS. 2, 3, 4, and 6 are circuit connection diagrams of current mirror circuits according to each embodiment of the present invention. 1.2, 8, 9, 10, 11. 14-24...
Transistor, 7... Resistor, Ba - Old... Plus side power supply line, Ca... Minus side power supply line. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure xy', Yz Y3

Claims (2)

[Claims] (1) A first transistor to which a reference current is supplied from the collector side and whose emitter is connected to one of the feed lines, whose base is connected to the pace of the first transistor, and whose emitter is connected to the feed line through a resistor. a third transistor complementary to the first and second transistors, the pace current being supplied from the collector of the second transistor;
a fourth transistor having an emitter connected to the emitter of the second transistor and having a base current supplied from the collector of the third transistor, and configured to take out an output current from the collector of the fourth transistor. A current mirror circuit characterized by: (2) A first transistor to which a reference current is supplied from the collector side and whose emitter is connected to one of the feed lines, and whose pace is connected to the base of the first transistor and whose emitter is connected to the feed line through a resistor. a third transistor which is complementary to the first and 'second transistors and whose base current is supplied from the collector of the second transistor; and whose emitter is connected to the collector of the second transistor; a fourth transistor connected to the emitter of the second transistor and having a base current supplied from the collector of the third transistor; a fourth transistor connected to the base of the fourth transistor and having an emitter connected to the feed line; A current mirror circuit comprising a sixth transistor configured to supply power to the collector of the fourth transistor from the other power supply line and to extract an output current from the collector of the sixth transistor. .