JPS5848922B2 - Fukugoutei Denriyu Cairo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to constant current circuits that are often used in transistor circuits, especially integrated circuits, and it is possible to control the amount of output current or relates to a composite constant current circuit that switches output current.

A constant current circuit generates a current equal to a predetermined current value or a current having a correlation such as being proportional to a predetermined current value,
The transistor circuit shown in FIG. 1 has been conventionally used to supply current as a current source.

Figures 1a and 1c are circuit connection diagrams showing three examples of typical conventional constant current circuits, where 1 is an input terminal, 2 is an output terminal, and 3 is a current supply terminal.

In Figure 1a, the input current supplied to input terminal 1 is
1 becomes the current flowing through the diode 4 and the base current of the transistor 50, and a collector current corresponding to the forward potential drop of the diode 4 flows through the transistor 5, giving an output current 2 to the output terminal 2.

In FIG. 1b, the diode 4 in FIG. 1a is replaced with a transistor 6 whose collector and base are coupled.
If the characteristics of transistors 5 and 6 are the same, a current approximately proportional to the emitter current density flows through each transistor.

Therefore, in the integrated circuit, the relationship between the input current I1 and the output current 2 can be set by appropriately selecting the shapes of the transistors 5 and 6, that is, the emitter area ratio.

FIG. 1C shows a constant current circuit using a lateral PNP transistor 7 having a multi-collector structure, and it is known that in this case, the current ratio is determined by the collector-emitter facing area ratio of each collector.

In FIG. 1b, transistor 5 and transistor 6
A type in which a resistor is inserted between each emitter and the current supply terminal 3 to stabilize the operation is also used, and a type configured with an NPN transistor with the polarity reversed is also used in exactly the same way. It is being said.

As explained above, in constant current circuits used in conventional integrated circuits, the output current has a substantially fixed value due to the design of the constant current circuit, and there is no means for freely controlling it from the outside.

An object of the present invention is to provide a composite constant current circuit whose output current can be controlled externally and which is suitable for integration into an integrated circuit.

Hereinafter, the present invention will be explained in detail by way of examples with reference to the drawings.

FIG. 2 is a block diagram of the composite constant current circuit of the present invention,
11 is a first constant current circuit, 12 is a second constant current circuit,
Each of them is composed of a constant current circuit as shown in FIG.

13 is a current I1 to the input terminal 16 of the second constant current circuit 12.
3 is the second current source that supplies 14, and 14 is the first constant current circuit 1
10 input terminal 18 and output terminal 1 of the second constant current circuit 12
a first current source connected to 7 and supplying a current I14, 1
5 is a load circuit or a next-stage circuit block connected to the output terminal 19 of the first constant current circuit 11 and through which the output current I15 flows.

The input terminal 18 of the first constant current circuit 110 is coupled to the output terminal 17 of the second constant current circuit 12, and then the first current source 1
4, the current I14 is the sum of the current II+ flowing to the input terminal 18 and the current I12 flowing to the output terminal 11.The following equation holds.As an example, if the first current source 14 is an input circuit, the current I14 is the sum of the current II+ flowing to the input terminal 18 and the current I12 flowing to the output terminal 11.
Assuming a circuit system in which the current 14 is transmitted to the current 15 through the first constant current circuit 11, the current I]5 becomes the current II+, that is, from the above equation (1), (II4 I12
), the current I15 flowing to the output circuit 15 can be controlled by changing the current I13 flowing through the second current source 13 that determines the current I12.

This means that the amount of current transmitted to the output circuit 15 can be freely controlled from the outside without affecting the operation of the first current source 14, which is the input circuit. By appropriately setting the relationship between the current I15 and the second constant current circuit 12 and the relationship between the first current source 14 and the second current source 13, the control gain and/or control range of the current I15 and the current I13 can be selected. It will be possible.

Further, the second current source 13 is used as an input circuit, and the first current source 1
The same thing can be said when controlling the output current I15 by changing the current I14 of No. 4.

A configuration in which a third constant current circuit and a third current source are further added to the block diagram of FIG. A current circuit can be constructed.

FIG. 3 is a circuit connection diagram showing one embodiment of the present invention, in which the output signal from the signal generation circuit 20 is transferred to the switching circuit 2.
A constant current circuit is applied to the signal switching circuit that outputs the signal to the output terminal 22 by the switching operation of step 1.

The signal generating circuit 20 is, for example, a PAL? The NPN transistor 2 may be a device that generates an alternating current signal such as a square wave or a square wave, or a device that generates a signal given as a direct current voltage.
It is directly connected to the collector of 3.

The emitter of the transistor 23 is grounded via a resistor 24 and simultaneously becomes an output terminal 22, and the base is a double collector PNP transistor 2 corresponding to the first constant current circuit.
5 to one collector.

The emitter of the transistor 25 is connected to the power supply terminal 26, and the base is coupled to the other collector to serve as an input terminal of the first constant current circuit, and is connected to the collector of the transistor 27.

The emitter of the transistor 27 is grounded via a resistor 28, and the transistor 27 is driven by the switching circuit 21 connected to the base to cause a current I27 to flow through the collector, thereby operating as a first current source.

Therefore, the switching circuit 21 causes the transistor 27 to
is biased and a current 2 flows, a corresponding current I25 flows into the base of the transistor 230, drives the transistor 23 into the saturation region, makes the collector-emitter conductive, and the output signal from the signal generation circuit 20 is It is taken out to the output terminal 22.

Furthermore, when the switching circuit 21 cuts off transistor 1 and transistor 2γ, transistor 25 and transistor 1 and transistor 23 are also cut off, and no signal appears at output terminal 22.

29 is a double collector PN corresponding to the second constant current circuit
It is a P transistor, and one collector is connected to the base of the l transistor 250 corresponding to the first constant current circuit, and the other collector is coupled to the base and connected to the collector of the l transistor 30.

The emitter of the transistor 30 is grounded via a resistor 31, and the base serves as an input terminal 32 to which a DC voltage for controlling the current is externally applied.

A current I30 determined by the DC voltage applied to the input terminal 32 flows through the collector of the transistor 30, which is 1.
An output current I29 corresponding to the input current to the transistor 290 flows out from one collector of the transistor 29.

Therefore, when the currents I25 and 2 are flowing and the transistor 23 is conducting, if a voltage is applied to the input terminal 32 and the current I29 is caused to flow, the current I25 becomes the current I3.
Since the change is almost proportional to the change in o, when forcing the transistor 23 into the cut-off state by the input voltage applied to the input terminal 32, the response speed can be reduced by giving a time constant to the change in input voltage. can be adjusted, and can also have the effect of suppressing shock noise when switching.

This has the effect of significantly reducing the adverse effects of shock noise that can be heard as shock noise, especially when this circuit is related to an audio signal system and the final stage is connected to a speaker.

FIG. 4 is a circuit connection diagram showing another embodiment of the present invention, and parts corresponding to those in FIG. 3 are designated by the same reference numerals.

In Fig. 4, 34 is the Schmitt 1-Riga circuit and the CR
A type of prosoking oscillation circuit using a combination of time constants.
The configuration is such that the transistor 25 and the transistor 33 are incorporated into the feedback loop of the oscillation circuit.

Current I flowing due to the switching operation of the oscillation circuit 34
35 is transmitted by the constant current transistor 25 to supply the base current I25 of the transistor 330, making the transistor 33 conductive and the collector current I33 flowing to the oscillation circuit 3.
4 will be returned.

That is, the oscillation operation of the oscillation circuit 340 is driven by the switching operation of the transistor 25 and the transistor 33, and when the transistor 25 and the transistor 33 are cut off, the oscillation is stopped.

Therefore, in FIG. 4, if the transistor 29 is connected to the transistor 25 in the same way as in FIG. It does not affect the normal working condition of the device.

In addition to the above embodiments, the present invention can be applied to various electronic circuits,
Especially when applied to integrated circuits, it is possible to apply integrated circuit technology that is advantageous due to the symmetry of elements, so it is possible to design highly accurate and rational circuits that have signal processing functions such as signal control and switching through current transmission. becomes possible.

[Brief explanation of drawings]

Fig. 1 a"c is a circuit connection diagram showing three examples of typical conventional constant current circuits, Fig. 2 is a block diagram of the composite constant current circuit of the present invention, and Figs. 3 and 4 are respectively in accordance with the present invention. It is a circuit connection diagram showing a specific example of L16, 18; input terminals of constant current circuit, 2, 17, 19
;Output terminal of constant current circuit, 3,26 ;Power supply terminal,
4; Diode, 5, 6, 23, 27, 30, 33
; NPN transistor, 7, 25, 29; double collector PNP } transistor, 11: first constant current circuit,
12: second constant current circuit, 13: second current source, 14:
First current source, 15: Load or next stage circuit block, 20
; Signal generation circuit, 21: Switching circuit, 22: Output terminal, 32: Input terminal, 24, 28, 31; Resistor, II
7 I22 Il3t Il4j II5+ I25
? I27) I29 t I30 + I33 t I3
5: Current, 34: Oscillation circuit.

Claims (1)

[Claims] 1 It has at least two constant current circuits that have a human power terminal and an output terminal, and a current proportional to the current supplied to the input terminal is obtained at the output terminal, and the output terminal of one of the constant current circuits is connected to a current source. and the input terminal of the other constant current circuit, a current corresponding to the difference between the current obtained at the output terminal of the one constant current circuit and the current of the current source is transferred to the other constant current. A composite constant current circuit characterized in that a current is obtained at the output terminal of the circuit.