JP4623936B2 - Constant current supply circuit for multiple remote loads - Google Patents

Description

【００４１】
シリコンダイオードＤ１の順方向電圧ＶＦ１の温度係数は一般的に −２mＶ／℃ であるので、（８）式の左辺がゼロになるように抵抗Ｒ３、Ｒ４、Ｒ５、ダイオードの個数ｎの値を決めれば、温度係数が殆どゼロとなる基準電圧生成回路２３を構成することができる。数値例として、例えば、次のように回路定数を決めると（８）式による基準電圧Ｖrefの温度係数を殆どゼロとすることができる。
Ｒ３＝１０ｋΩ 、Ｒ４＝１００ｋΩ 、Ｒ５＝１０ｋΩ 、ｎ＝１
【００４２】
【図面の簡単な説明】
【図１】 本発明の第１の実施形態である定電流供給回路の電気的構成図である。
【図２】 基準電圧生成回路２０の動作点の求め方を説明する図である。
【図３】 本発明の第２の実施形態である定電流供給回路の電気的構成図である。
【図４】 従来技術を示す図１相当図である。
【符号の説明】
図面中、１０、２２は定電流供給回路、１１は手元回路、１２は遠隔回路、１３は電源線、１４は接地線、１５はベース信号線、１６は帰還電流生成回路、１７は負荷電流帰還線、１８a、１８ｂ、１８cは負荷駆動回路、１９は直流電源、２１は誤差増幅回路、２３はバンドギャップ基準電圧生成回路、Ｄ１、Ｄ２１、Ｄ２ｎはダイオード、Ｉc４〜６はコレクタ電流（負荷駆動回路の出力電流）、Ｉc７は帰還電流、Ｉbtはベース電流の総量、ＯＰ２は演算増幅器、Ｒ１は第１の抵抗、Ｒ２は第２の抵抗、Ｒ３は第３の抵抗、Ｒ４は第４の抵抗、Ｒ５は第５の抵抗、ＲＬ４〜６は負荷抵抗、Ｒr４〜７は抵抗、Ｒrefは基準抵抗、Ｔ３は第１のＮＰＮトランジスタ、Ｔ４は第２のＮＰＮトランジスタ、Ｔ５は第３のＰＮＰトランジスタ、Ｔ６は第４のＰＮＰトランジスタ、Ｔr４〜７はＰＮＰトランジスタ、Ｖfは帰還電圧、Ｖrefは基準電圧を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a constant current supply circuit for supplying a predetermined DC constant current from a DC power supply in a local circuit to one or a plurality of loads at remote locations.
[0002]
[Prior art]
Supplying the same constant DC current to multiple remote sensing elements such as thermistors and strain gauges for vehicle operation control, motion analysis of machine equipment and building structures, and grasping operation status You may need it. FIG. 4 is an example of a constant current supply circuit used in such a case.
[0003]
The conventional constant current supply circuit 1 includes a hand circuit 2 and a remote circuit 3 placed near a load. The remote circuit 3 is supplied with the power supply voltage Vdd from the DC power supply 7 in the hand circuit 2 through the long power supply line 4 and the ground line 5. Collector currents Ic1, Ic2, and Ic3 of PNP transistors Tr1, Tr2, and Tr3 whose emitters are connected to the power supply line 4 are supplied to the loads RL1 to RL3, respectively. The remote circuit 3 in FIG. 4 illustrates the case where the number of loads is three.
[0004]
The hand circuit 2 includes a DC power source 7 , a PNP transistor T 1, and a constant current source 6. The DC power supply 7 supplies a DC voltage Vdd between the power supply line 4 and the ground line 5. The ground line 5 is connected to the ground node Vss. The emitter of the PNP transistor T1 is connected to the power supply line 4, and a constant current source 6 for supplying a constant current Ia as a reference current is connected between the collector and the ground node Vss toward the ground node Vss. . The base of the transistor T1 is connected in common to the bases of the transistors Tr1 to Tr3 in the remote circuit 3 by the base signal line 8, and is also connected to the collector of the transistor T1.
[0005]
With this connection, the transistors T1 and Tr1, T1 and Tr2, and T1 and Tr3 form a current mirror circuit. Therefore, when the characteristics of the transistors are the same, the current amplification factor is sufficiently high, and the wiring resistances of the power supply line 4 and the ground line 5 are sufficiently low, the currents Ic1 to 3 flowing through the loads RL1 to RL3 are all It becomes equal to the current Ia supplied from the constant current source 6. That is, the same current as the current Ia that is the reference current supplied from the constant current source 6 is supplied to the loads RL1 to RL3.
[0006]
However, the problem here is the wiring resistance of the power supply line 4. When the distance between the hand circuit 2 and the remote circuit 3 is long, the wiring resistance of the power line 4 cannot be ignored, and the voltage applied to the emitters of the transistors Tr1 to 3 of the remote circuit 3 due to the voltage drop due to the wiring resistance. It becomes lower than Vdd. That is, the emitter-base voltage of each of the transistors Tr1 to 3 of the remote circuit 3 is lower than the emitter-base voltage of the transistor T1 of the local circuit 2 by the voltage drop caused by the power line 4. As a result, the base currents of the transistors Tr1 to Tr3 are smaller than the base current of the transistor T1, and the values of the load currents Ic1 to 3 are smaller than the reference current Ia. Therefore, the same current as the reference current Ia cannot be passed through the loads IL1 to IL3.
[0007]
Further, when the number of loads RL increases, the base current Ib flowing into the constant current source 6 increases, so the collector current Ic of the transistor T1 decreases conversely. As a result, the values of the collector currents Ic1 to 3 of the transistors Tr1 to 3 forming a current mirror with the transistor T1 are also reduced. Therefore, this also increases the difference between the reference current Ia and the load currents Ic1 to Ic3.
[0008]
[Problems to be solved by the invention]
The present invention has been made to solve such problems of the conventional circuit, and its purpose is to increase the wiring resistance of the power supply line for supplying power from the local circuit to the remote circuit and the return ground line. Another object of the present invention is to provide a constant current supply circuit capable of supplying a constant current equal to a target reference current to each load even when the number of loads is large.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a constant current supply circuit for supplying a predetermined constant current to one or more remote loads, comprising a power line, a ground line, a base signal line, and It is composed of a local circuit and a remote circuit connected to each other by a load current feedback line. The remote circuit includes one or more load driving circuits in which a resistor having one end connected to a power supply line and a PNP transistor are connected in series. The collector current of the transistor in the circuit is supplied as an output current to a load having one end connected to the ground line. Furthermore, a feedback current generation circuit having the same configuration as the load drive circuit is provided, and the output current is fed back to the local circuit as a feedback current via the load current feedback line. The hand circuit includes a DC power source, a reference voltage generation circuit, an error amplification circuit, and a reference resistor. A DC power supply supplies a DC voltage to the remote circuit via the power line and the ground line. The reference resistor has one end connected to the ground line and the other end receiving the feedback current, and generates a feedback voltage proportional to the feedback current at both ends. The error amplifying circuit amplifies a difference voltage between the reference voltage generated by the reference voltage generation circuit and the feedback voltage, and outputs the difference between the one or more load driving circuits and the PNP transistors in the feedback current generation circuit. The total amount of base current drawn from the base signal lines connected to the base in common is controlled. A constant current supply circuit configured to supply a constant current obtained by dividing the reference voltage by the value of the reference resistance to each load connected to the load driving circuit by this control.
[0010]
According to such a configuration, a predetermined constant current can be supplied to one or more remote loads without being affected by the wiring resistance of the power supply line.
[0011]
The invention described in claim 2 is characterized in that the reference voltage generating circuit used in the constant current supply circuit described in claim 1 is configured as follows. That is, the reference voltage generation circuit includes a first NPN transistor whose emitter is connected to a ground line, a first resistor connected between the base and emitter of the transistor, and a base and emitter each of which is the first transistor. A second NPN transistor connected to the collector and base of the transistor, an emitter connected to the power line, a third PNP transistor connected to the collector of the first transistor, an emitter connected to the power line, and a collector A fourth PNP transistor connected to a base, a base of the third PNP transistor, and a collector of the second NPN transistor; a second resistor connected to a power supply line and a collector of the first NPN transistor; And a circuit using the voltage between the base of the first transistor and the ground line as the reference voltage A.
[0012]
This circuit is a self-bias type constant current circuit, and a constant current that is hardly affected by the power supply voltage flows through the first resistor. Therefore, the voltage across the first resistor can be used as a reference voltage. it can. By using the reference voltage generation circuit having such a configuration for the constant current supply circuit according to the first aspect, it is possible to obtain the same effect as that of the invention according to the first aspect.
[0013]
According to a third aspect of the present invention, the reference voltage generation circuit used in the constant current supply circuit according to the first aspect is configured by a band gap reference voltage generation circuit.
[0014]
The band gap reference voltage generation circuit can generate a reference voltage whose temperature coefficient of the reference voltage is almost zero. Therefore, if such a circuit is used as the reference voltage generation circuit, the same effect as that of the first aspect of the invention can be obtained.
[0015]
According to a fourth aspect of the present invention, the reference voltage generation circuit used in the constant current supply circuit according to the first aspect is configured by a band gap reference voltage generation circuit having the following specific configuration. The constant current supply circuit is characterized in that the circuit constant is determined so that the temperature coefficient of the generated reference voltage is almost zero. That is, the reference voltage generation circuit includes an operational amplifier, a third resistor connected between the output terminal and the non-inverting input terminal of the operational amplifier, and the output terminal and the inverting input terminal of the operational amplifier. A fourth resistor connected; a diode having an anode connected to the non-inverting input terminal and a cathode grounded; and a diode having the same specification as the diode, the cathode grounded and the anode commonly connected It comprises a plurality of diodes and a fifth resistor connected between the anodes of the one or more diodes and the inverting input terminal, and uses the output of the operational amplifier as a reference voltage. In addition, the values of the third, fourth, and fifth resistors and the number of the one or more diodes are adjusted so that the temperature coefficient (V / ° C.) of the output reference voltage becomes zero. is there.
[0016]
If the reference voltage generating circuit having such a configuration is employed in the constant current circuit according to claim 1, the plurality of remote loads are hardly affected by temperature and are influenced by the wiring resistance of the power supply line in the middle. Without receiving the same load current.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A first embodiment of the present invention will be described with reference to FIG. The constant current supply circuit 10 of the present embodiment is also composed of a hand circuit 11 and a remote circuit 12 as in FIG. The remote circuit 12 is a circuit placed near the load. The hand circuit 11 and the remote circuit 12 are connected in common to a power line 13 and a ground line 14 for supplying a power supply voltage Vdd, and bases of PNP transistors Tr4 to 7 to be described later in the remote circuit 12, and bases of these transistors Tr4 to 7 The base signal line 15 that leads the current sum Ibt to the hand circuit and the load current feedback line 17 that feeds back an output current Ic7 of a feedback current generating circuit 16 described later to the hand circuit 11 are connected to each other.
[0018]
The remote circuit 12 includes a feedback current generation circuit 16 and three types of load drive circuits 18a, 18b, and 18c. The three load drive circuits are illustrative, and the number is increased or decreased as necessary. The load is an example of three cases of RL4, RL5, and RL6.
[0019]
The load drive circuit 18a includes a resistor Rr4 and a PNP transistor Tr4. One end of the resistor Rr4 is connected to the power supply line 13, and the other end is connected to the emitter of the transistor Tr4. The collector of the transistor Tr4 is connected to one end of the load RL4, and the other end of the load RL4 is connected to the ground line 14. The collector current Ic4 of the transistor Tr4 is supplied to the load RL4 as a load current. The other load drive circuits 18b and 18c are the same as the load drive circuit 18a.
[0020]
The feedback current generation circuit 16 has the same circuit configuration and circuit constant as the load drive circuit 18a. However, the collector current Ic7 of the output transistor Tr7 is configured to flow to the hand circuit 11 side through the load current feedback line 17 instead of the load.
[0021]
The bases of the output transistors Tr4 to Tr6 in the load driving circuits 18a, 18b, and 18c and the output transistor Tr7 in the feedback current generating circuit 16 are connected in common, and the base current Ibt that flows out of these bases is the base signal line 15 Through the hand circuit 11 side.
[0022]
The hand circuit 11 includes a DC power source 19, a reference voltage generation circuit 20, an error amplification circuit 21, and a reference resistor Rref. The DC power supply 19 supplies a DC voltage Vdd to the power supply line 13. The negative side is connected to the ground node Vss. A ground line 14 is also connected to the ground node Vss.
[0023]
One end of the reference resistor Rref is connected to the ground node Vss, and the other end is connected to the load current feedback line 17. The output current Ic7 of the feedback current generating circuit 16 in the remote circuit 12 flows, and a feedback voltage is applied to both ends thereof. Vf is generated.
[0024]
The error amplifier circuit 21 includes an operational amplifier OP1 and an NPN transistor T2 having a base connected to the output terminal thereof. The collector of the transistor T2 is connected to the base signal line 15, and the emitter is connected to the ground node Vss. The reference voltage Vref generated by the reference voltage generation circuit 20 is input to the non-inverting input terminal of the operational amplifier OP1, and the feedback voltage Vf is input to the inverting input terminal. A differential voltage between the reference voltage Vref and the feedback voltage Vf is amplified by the operational amplifier OP1, and a voltage proportional to the differential voltage is output, so that a base current flows through the transistor T2. The base current is amplified by the transistor T2, and its collector attracts the base current Ibt flowing into the base signal line 15 and flows it to the ground node Vss.
[0025]
Since the voltage amplification factor of the operational amplifier OP1 is set to a sufficiently high value, the amount of the base current Ibt drawn from the base signal line 15 is controlled so that the feedback voltage Vf becomes equal to the reference voltage Vref. By this feedback control, the value of the output current Ic7 of the feedback current generation circuit 16 becomes equal to the value obtained by dividing the reference voltage Vref by the reference resistor Rref.
[0026]
The circuit configurations and circuit constants of the load drive circuits 18a, 18b, and 18c are the same as those of the feedback current generation circuit 16. The output impedances of the transistors Tr4-7, which are the output transistors of these circuits, are sufficiently high and their bases are connected in common, so that the same base current flows through each of the transistors Tr4-7. Therefore, the values of the collector currents Ic 4 to 7 supplied to the loads RL 4 to 6 are all equal to the output current Ic 7 of the feedback current generation circuit 16. That is, a constant current Ic7 equal to a reference current (a value obtained by dividing the reference voltage Vref by the reference resistance Rref) is supplied to the loads RL4 to RL7.
[0027]
The value of the constant current Ic7 is determined only by the values of the reference voltage Vref and the reference resistance Rref, and is not affected by the wiring resistance of the power supply line 13 and the ground line 14. Accordingly, the currents Ic4-7 flowing through the loads RL4-7 are not affected by them. Furthermore, since the constant current Ic7 is not affected by the fluctuation of the power supply voltage Vdd , the load currents Ic4 to 7 are not affected.
[0028]
Here, the resistors Rr4-7 connected to the emitters of the transistors Tr4-7 suppress variations in the collector currents Ic4-7 caused by variations in the base-emitter voltage of the transistors Tr4-7 and variations in the current amplification factor. It works as a current feedback. Therefore, when the variation of the collector currents Ic4 to 7 is not so much a problem, these resistors may be removed and the portion may be short-circuited.
[0029]
Since the transistor T2 is for amplifying the output current of the operational amplifier OP1, when the output current capacity of the operational amplifier OP1 is sufficiently high, the transistor T2 is removed and the output terminal of the operational amplifier OP1 is used as a base. The signal line 15 may be directly connected. In this case, however, the reference voltage Vref is input to the inverting input terminal of the operational amplifier OP1, and the feedback voltage Vf is input to the non-inverting input terminal.
[0030]
Next, the reference voltage generation circuit 20 will be described. The reference voltage generation circuit 20 is a self-bias type constant current circuit, and includes first and second NPN transistors T3 and T4, third and fourth PNP transistors T5 and T6, and first and second resistors R1. , R2.
[0031]
The emitter of the first transistor T3 is connected to the ground node Vss, and the first resistor R1 is connected between the base and the emitter. The base and emitter of the second transistor T4 are connected to the collector and base of the first transistor T3, respectively. The current flowing into the interconnection node N1 between the collector of the first transistor T3 and the base of the second transistor T4 is I1, the current flowing into the collector of the second transistor T4 is I2, and between the base and emitter of the first transistor T3 Assuming that the voltage is Vbe and the base current of each transistor is very small, there is the following relationship between the currents I2 and I1.
I2 = Vbe / R1 = ((k · T / q) · Ln (I1 / Is1)) / R1 (1) where k is the Boltzmann constant, T is the absolute temperature, q is the charge of the electron, Is1 is the first 1 is a reverse saturation current of one transistor T3, and Ln represents a natural logarithm.
[0032]
On the other hand, the third and fourth transistors T5 and T6 connected as loads of the first and second transistors T3 and T4 form a known current mirror circuit. Therefore, when the current flowing through the second resistor R2 connected between the power supply line 13 and the collector of the first transistor T3 is ignored, the following relationship is established.
I2 = I1 (2) Formula
When solving these equations (1) and (2) as simultaneous equations, the value of the current I2 at the operating point of the reference voltage generation circuit 20 is obtained. To actually solve this simultaneous equation, as shown in FIG. 2, the curve of the formula (1) and the straight line of the formula (2) are drawn on the coordinate with the current I1 on the horizontal axis and I2 on the vertical axis. What is necessary is just to obtain | require the value of the electric currents I2 and I1 in an intersection (operation point). The second resistor R2 operates as a start-up circuit, and immediately after the power is turned on, the reference voltage generation circuit 20 is prevented from being stabilized when both the currents I1 and I2 are zero. This is for flowing a small amount of current through the first transistor T3. The current flowing through the resistor R2 is set to a high resistance value so as to be a value much smaller than the currents I1 and I2 (in addition, various other circuits have been proposed as a starting circuit).
[0034]
The value of the current I2 obtained in this way is a constant value determined only by the value of the first resistor R1 and the absolute temperature T of the first transistor T3, and is a value that is hardly affected by the power supply voltage Vdd. Accordingly, the voltage across the first resistor R1, in other words, the base-emitter voltage Vbe of the first transistor T3 becomes a constant value Vref as follows. In this way, the reference voltage generation circuit 20 shown in FIG. 1 operates as a reference voltage generation circuit that generates the following reference voltage Vref.
Vref = R1 · I2 (3) Formula
(Second Embodiment)
A second embodiment of the present invention will be described with reference to FIG. The same or corresponding parts as those in FIG. Since the constant current supply circuit 22 of the present embodiment is the same as the circuit configuration of FIG. 1 of the first embodiment except for the reference voltage generation circuit 23, only the different reference voltage generation circuit 23 will be described.
[0036]
The reference voltage generation circuit 23 used in this embodiment is called a bandgap reference voltage generation circuit. In the band gap reference voltage generation circuit, a current source based on the forward voltage Vbe between the base and emitter of the transistor has a negative temperature coefficient, and a current source based on the absolute temperature T of the transistor has a positive temperature coefficient. Therefore, the current generated by the two current sources is weighted and added to create a combined reference voltage with a temperature coefficient of zero.
[0037]
Various circuit formats have been proposed for the band gap reference voltage generation circuit, and the reference voltage generation circuit 23 in FIG. 3 is an example. The reference voltage generation circuit 23 in FIG. 3 includes an operational amplifier OP2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a diode D1, and one or more diodes D21 to D2n. .
[0038]
A third resistor R3 is connected between the output terminal and the non-inverting input terminal of the operational amplifier OP2, and a fourth resistor R4 is connected between the output terminal and the inverting input terminal. A diode D1 is connected between the non-inverting input terminal and the ground node Vss with the anode as the non-inverting input terminal side. A diode group D21 to D2n in which one or a plurality (n) of diodes having the same specifications as the diode D1 are connected in parallel is grounded with the cathode as the ground node Vss side, and between the anode terminal group and the inverting input terminal of the operational amplifier OP2. Is connected to a fifth resistor R5.
[0039]
Here, assuming that the currents flowing through the third resistor R3 and the fourth resistor R4 toward the ground node Vss are I3 and I4, their values are approximated by the following equations.
I3 = IS3 · exp (q · VF1 / kT) (4) Equation I4 = IS4 · exp (q · VF2 / kT) (5) Equation where IS3 is the reverse saturation current of the diode D1, and IS4 is the diodes D21 to D2n VF1 is a forward voltage of the diode D1, VF2 is a forward voltage of the diodes D21 to D2n, q is an electron charge, k is a Boltzmann constant, and T is an absolute temperature.
[0040]
Since the diodes D1, D21 to D2n are diodes having the same specification, the following relationship exists between IS3 and IS4.
IS4 = n · IS3 (6) Expression When the output reference voltage Vref of the reference voltage generation circuit 23 is calculated using these expressions (4) to (6), the following is obtained.
Vref = VF1 + (R4 / R5). (KT / q) Ln (n.R4 / R3)
Equation (7) From this equation (7), the temperature coefficient (V / ° C.) of the reference voltage Vref is expressed by the following equation.
[Formula 1]

[0041]
Since the temperature coefficient of the forward voltage VF1 of the silicon diode D1 is generally −2 mV / ° C., the values of the resistors R3, R4, R5 and the number of diodes n can be determined so that the left side of the equation (8) becomes zero. For example, the reference voltage generation circuit 23 having a temperature coefficient of almost zero can be configured. As a numerical example, for example, if the circuit constant is determined as follows, the temperature coefficient of the reference voltage Vref according to the equation (8) can be made almost zero.
R3 = 10 kΩ, R4 = 100 kΩ, R5 = 10 kΩ, n = 1
[0042]
[Brief description of the drawings]
FIG. 1 is an electrical configuration diagram of a constant current supply circuit according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining how to obtain an operating point of a reference voltage generation circuit 20;
FIG. 3 is an electrical configuration diagram of a constant current supply circuit according to a second embodiment of the present invention.
FIG. 4 is a view corresponding to FIG.
[Explanation of symbols]
In the drawing, 10 and 22 are constant current supply circuits, 11 is a hand circuit, 12 is a remote circuit, 13 is a power supply line, 14 is a ground line, 15 is a base signal line, 16 is a feedback current generation circuit, and 17 is a load current feedback. 18a, 18b and 18c are load drive circuits, 19 is a DC power supply, 21 is an error amplification circuit, 23 is a band gap reference voltage generation circuit, D1, D21 and D2n are diodes, and Ic4 to 6 are collector currents (load drive circuit). Output current), Ic7 is a feedback current, Ibt is a total amount of base current, OP2 is an operational amplifier, R1 is a first resistor, R2 is a second resistor, R3 is a third resistor, R4 is a fourth resistor, R5 is a fifth resistor, RL4-6 are load resistors, Rr4-7 are resistors, Rref is a reference resistor, T3 is a first NPN transistor, T4 is a second NPN transistor, T5 is a third PNP transistor, T6 Is the fourth PNP transistors, Tr4 to Tr7 are PNP transistors, Vf is a feedback voltage, and Vref is a reference voltage.

Claims (4)

A constant current supply circuit for supplying a predetermined constant current to one or a plurality of remote loads, wherein a local circuit and a remote circuit are mutually connected by a power line, a ground line, a base signal line, and a load current feedback line And
The remote circuit is configured to connect a resistor having one end connected to a power supply line and a PNP transistor in series, and supply a collector current of the transistor as an output current to a load having one end connected to a ground line. Or a plurality of load drive circuits, and a circuit that is the same as the load drive circuit, and that includes a feedback current generation circuit that feeds back the output current as a feedback current to the local circuit via the load current feedback line And
The hand circuit includes a DC power supply, a reference voltage generation circuit, an error amplification circuit, and a reference resistor, and the DC power supply supplies a DC voltage to the remote circuit via the power supply line and a ground line. The reference resistor is configured so that one end is connected to a ground line, the other end receives the feedback current, and the other end generates a feedback voltage proportional to the feedback current. The base voltage of the PNP transistor in the feedback current generating circuit is shared by the one or more load driving circuits by amplifying the difference voltage between the reference voltage generated by the reference voltage generating circuit and the feedback voltage Is configured to control the total amount of base current drawn from the base signal line connected to
A constant current supply circuit configured to supply a constant current obtained by dividing the reference voltage by a value of the reference resistance to each load connected to the load driving circuit by the control. The reference voltage generation circuit includes a first NPN transistor having an emitter connected to the ground line, a first resistor connected between a base and an emitter of the transistor, and a base and an emitter each being the first transistor. A second NPN transistor connected to the collector and base of the transistor, an emitter connected to the power line, a third PNP transistor connected to the collector of the first transistor, an emitter connected to the power line, and a collector A fourth PNP transistor connected to its own base, a base of the third PNP transistor and a collector of the second NPN transistor, and a power source line and a collector of the first NPN transistor. And a voltage between the base of the first transistor and the ground line. Constant current supply circuit according to claim 1, characterized in that the circuit for the reference voltage. The constant current supply circuit according to claim 1, wherein the reference voltage generation circuit includes a band gap reference voltage generation circuit. The reference voltage generation circuit is connected between the operational amplifier, a third resistor connected between the output terminal and the non-inverting input terminal of the operational amplifier, and between the output terminal and the inverting input terminal of the operational amplifier. A fourth resistor, a diode having an anode connected to the non-inverting input terminal and a cathode grounded, and a diode having the same specifications as the diode, the cathode grounded and the anode commonly connected And a fifth resistor connected between the anode of the one or more diodes and the inverting input terminal, and a bandgap reference voltage generation circuit using the output of the operational amplifier as the reference voltage And the values of the third, fourth, and fifth resistors so that the temperature coefficient (V / ° C.) of the reference voltage output from the reference voltage generation circuit is zero. Constant current supply circuit according to claim 1, wherein the number of fine said one or a plurality of diodes is one that was adjusted.

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