JPS62254218A - Constant current circuit - Google Patents

Abstract

PURPOSE:To ensure a stable supply of a constant current despite the drop of the power supply voltage by increasing the gain of a constant current circuit. CONSTITUTION:When the voltage is applied to a power supply VCC, a current flows to a diode element 2 of a transistor TR whose base and collector are connected via a resistance 1. The value of the current flows to the element 2 is small because the resistance 1 has high resistance value. At the same time, a current flows also to a TR4 as well as to a diode element 5 of a TR having a connected diode. Thus, the current flows to both TR9 and 10 and then to a diode element 11 and a TR8. Then a current flows to a TR6 for start of an operation. In this case, the current amplification factors of both TR9 and 10 are set at about '1'. However, it is possible to secure the stable supply of current despite a low level of voltage because the current gains are secured by both TR8 and 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a constant current circuit used when constructing an electronic circuit such as a semiconductor integrated circuit.

Conventional technology FIG. 4 shows a conventional constant current circuit.

In Fig. 4, 1.3, 7, 15, 16.17 are resistors, 4, 8, 10.12 are transistors, 2.6.11 are diode elements such as diode-connected transistors and diodes, 13 is a circuit, vo.

is the power supply.

The operation of the constant current circuit configured as described above will be explained below.

Power supply V. . When voltage is applied to the base,
A current flows through the diode element 2 of the transistor whose collector is connected. This resistor 1 has a high resistance (for example, 200Ω
), a small amount of current flows through the diode element 2, a current also flows through the transistor 4, and a current also flows through the diode element 6 of the diode-connected transistor. Then, transistor 10. Diode connected transistor 1
A current also flows through the 1° transistor 8 and it begins to operate.

At this time, the voltage across the diode-connected transistor 110 (potential vax between the base and emitter) is the value C shown in FIG. 6, which is the base of the transistor 8.

Emitter voltage V. is the value of D, and resistor 7 is 200
Let it be Ω. At this time, diode element 5 and transistor 1
When the voltages VBE between the base and emitter of the transistor o are approximately equal, approximately the same current flows through the transistor 10 and the diode-connected transistor 6.

Therefore, when a current of 1 mm flows through the diode-connected transistor 11, a current of 1 mm also tends to flow through the transistor 8. In this case, since resistor 7 is 200Ω, resistor 7
A voltage drop of α2v occurs.

When the potential between the base and emitter of the diode-connected transistor 11 is 0.7V, the sum of the voltage 0.2V of the resistor 7 and the voltage o, sV between the base and emitter of the transistor 8 is 0.7V, and this constant current The current in the circuit is approximately 111I
It operates stably in the system. 111I for transistor 12
A current can flow to supply current to the circuit 13.

Problems to be Solved by the Invention However, in the above configuration, the transistor/10,
8. Since the gain of the loop of the diode-connected transistor 11.6 is low, there is a problem in that the current drops quickly when the power supply v0.degree. drops to about 1V.

In view of the above problems, the present invention provides a constant current circuit that stably supplies a constant current even when the power supply voltage decreases.

Means for Solving the Problems In order to solve the above problems, the constant current circuit of the present invention has a first diode element such as a diode-connected transistor or a diode, and a voltage V between the base and the emitter of the first diode element. a first transistor configured to have a higher voltage than a diode element; and one of the diode elements is connected to the base of the first transistor and the collector of a second transistor having a polarity different from that of the first transistor. ,
A first resistor is connected between the other of the first diode elements and the emitter of the first transistor, the emitter of the first transistor is connected to one power supply, and the collector of the first transistor is connected to the first resistor. A third transistor having a polarity different from that of the transistor is connected, and one of the second diode elements such as a diode-connected transistor or diode is connected to the second transistor. The third transistor is connected to the base of the third transistor and the collector of the fourth transistor has the same polarity as the first transistor, and the other of the second diode elements is connected directly or to the second diode element.
Connect to the other power supply through the resistor.

The emitters of the second and third transistors can be connected directly or directly to the emitters of the second and third transistors.
It is connected to the other power supply through the fourth resistor, the collectors of the first and third transistors are connected to the base of the transistor of fJc4, and the emitter of the fourth transistor is connected directly or through the sixth resistor to one of the power supplies. According to the present invention, the gain of the constant current circuit is increased using the above-described configuration to stably flow a constant current down to a low voltage.

Example A constant current circuit according to an embodiment of the present invention will be explained below.

This will be explained with reference to the drawings. FIG. 1 shows a constant current circuit in one embodiment of the present invention.

In FIG. 1, '13.19 is a resistor, 2j6°11 is a diode element such as a diode-connected transistor or diode, 4,6,8,9,10°12 is a transistor, 13 is a circuit, and vo. is the power supply.

Regarding the constant current circuit configured as above, the following is the first section.
The operation will be explained using FIG. When a voltage is applied to the power supply v0°, a current flows through the diode element 2 of the transistor whose base and collector are connected through the resistor 1.Since this resistor 1 has a high resistance, a small current flows to the diode element 2, and the transistor A current also flows through the diode element 4, and a current also flows through the diode element 6 of the diode-connected transistor. Then, current flows through transistors 9 and 1o, and diode elements 11. A current flows into transistor 8, and a current flows into transistor 6, which starts operating. Resistance at this time 1. Diode element 2. Transistor 4. The resistor 3 is a starting circuit that allows a small amount of current to flow in order to start the operation of the constant current circuit.

At this time, the voltage between both ends (base-emitter voltage VBE) of the diode-connected transistor 11 is the value D shown in FIG. 6, and the transistor 80 pace.

The emitter voltage VBE is the value of C, and the resistor 19 is 2
00Ω. At this time, when the voltages VBE between the diode element 6 and the bases and emitters of the transistors 9 and 1o are substantially equal, substantially the same current flows through the transistors 9 and 10 and the diode-connected transistor 6. Therefore, when a current of 111 im flows through the diode-connected transistor 11, a current of 1 m also tends to flow through the transistor 8. In this case, since the resistance 19 is 200Ω, the resistance 19 is 0.
A voltage drop of 2V is generated between the base and emitter potential o0gV of the diode-connected transistor 11 and the resistor 19.
The sum of the voltage of 0.2v is 0. Since it becomes a TV and the voltage between the base and emitter of the transistor 8 is 0.7V, it becomes a balanced state and the current tends to stabilize at approximately 1 mm.

However, if the currents of transistors 9 and 8 are the same, no current will flow to transistor 6, so in order to make a current of about 1 mm flow through transistor 6 and diode element 6, the base current of transistor 6 (Ho of transistor 6 100
) is about 10 .mu.m, and the balance is such that 10 .mu.m more flows in transistor 9 than in transistor 8. Therefore, this constant current circuit operates stably with a current of approximately 1 mm, rather than exactly 1 mm. At this time, the transistor 12 is connected as shown in FIG. 1, and current can be supplied to the electronic circuit 13 to operate the circuit with a constant current.

In the conventional example shown in FIG. 4, in the configuration of diode element 6 and transistor 1o, the current amplification degree is about 1 T, and only transistor 8 has a current gain of 0. However, in the present invention, the current amplification degree of diode element 6 and transistors 9 and 10 is is about 1, but since it has a current gain due to transistor 8 and a current gain due to transistor 6, it is possible to stably flow a current even at a low voltage, for example, a low voltage of around 1 V. This state is shown in Fig. 5. In the conventional circuit shown in Fig. 4, the circuit becomes as shown in Fig. 5, but in the configuration shown in Fig. 1 of the present invention, the current change is small down to low voltages as shown in Fig. 6, B. Operates as a stable circuit 0 As described above, according to this embodiment, the structure is not very complicated, and the structure has a current gain, and can operate stably down to low voltages.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a constant current circuit showing a second embodiment of the present invention. In the figure, the difference from Figure 1 is that the electronic circuit 1
A transistor 14 is used to supply current to the diode element 3, and almost the same current as that of the diode element 11 can be passed through the transistor 14.

As described above, in the embodiment shown in FIG. 2, the circuit is operated based on a power source different from that in FIG. 1.

Further, a third embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows a constant current circuit showing a second embodiment of the present invention. In this figure, the difference from Figure 1 is that the resistor 14
, 16, 16.17 and 18 have been added.

As mentioned above, in the embodiment shown in FIG. 3, the resistor 14.1 in FIG.
5, 16, and 17 are added to reduce current changes due to variations in the voltage of the diode element 6 and the contact potential v8 between the base and emitter of the transistors 9, 10, and 12.

The resistor 18 is added to adjust the current gain when the gain of the transistor 6 is too high and abnormal oscillation occurs. Even if a resistor 2o is added, the same operation will occur.0 Effects of the Invention As described above, the present invention uses two transistors having a current gain to provide a 1V voltage without making the circuit configuration too complicated.
It can supply a constant current that operates stably down to nearby low voltages.

[Brief explanation of drawings]

FIG. 6 is an explanatory diagram showing the current characteristics of a constant current circuit, and FIG. 6 is an explanatory diagram showing the characteristics of the contact potential VBE between the base and emitter of a transistor and the voltage of a diode element. 1.3, 7, 15, 16, 17, 18, 19°2o...
...Resistance, 2,5,11...Diode element, 4.6. B, 9, 10, 12.14- - Transistor, 13... Electronic circuit. Name of agent: Patent attorney Toshio Nakao and one other person4.
6. δ,? , to, ft--L run,-suyFigure 2Figure 3Figure 4

Claims (1)

[Claims] The first of diode-connected transistors, diodes, etc.
Voltage V_B between the diode element, base and emitter
a first transistor configured such that _E has a higher voltage than the first diode element, and a second transistor in which one of the diode elements has a base of the first transistor and a polarity different from that of the first transistor. A first resistor is connected between the other of the first diode elements and the emitter of the first transistor, the emitter of the first transistor is connected to one power supply, and the first resistor is connected to the collector of the first diode element. The collector of a third transistor having a polarity different from that of the first transistor is connected to the collector of the transistor, and one of the second diode elements such as a diode-connected transistor or diode is connected to the base of the second and third transistors and the collector of a third transistor whose polarity is different from that of the first transistor. the collector of the fourth transistor having the same polarity as that of the first transistor; the other of the second diode elements is connected to the other power supply directly or through a second resistor; The emitters of the transistors are connected directly or through the third and fourth resistors to the other power supply, the collectors of the first and third transistors are connected to the base of the fourth transistor, and the emitters of the fourth transistor are connected directly to the other power supply. Or a constant current circuit characterized in that it is connected to one power source via a fifth resistor.