JP2000250645A - Constant current circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a constant current circuit which operates stably and can supply a constant current in accordance with the control signal voltage even when the input/output characteristic of a control transister or a wiring resistance varies. SOLUTION: This circuit consists of the modules 10a-10j of the same constitution, and a constant current is supplied to a load terminal 2 in accordance with the control signal voltage supplied to a control input terminal 1. In each of the modules 10a-10j, the drain of an Nch type MOS transistor Tr1 is connected to an output terminal 12 and an operational amplifier 15 is connected to the gate of the Tr1. A source current I1a is detected by a current detection resistance R1 and a differential amplifier 16, controlled by the negative feedback action of the amplifier 15 and not affected by a wiring resistance R2a. The negative feedback is carried out on each module to keep the constant control characteristic of the module. Therefore the current I1a has no variance despite the variance in the input/output characteristic of the Tr1. Thus, the Tr1 never exceeds the highest bonding temperature nor the highest drain current standard.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a constant current circuit for supplying a constant current according to a control signal voltage, and more particularly to a constant current circuit for supplying a large capacity constant current.

[0002]

2. Description of the Related Art As a conventional constant current circuit, for example, FIG.
There is a suction-type constant current circuit shown in FIG. In this constant current circuit, the control signal voltage V input from the control input terminal 31
A constant current corresponding to i ′ is drawn from the load terminal 32 and flows to the ground terminal 33. First, the control signal voltage Vi ′ is supplied from the control input terminal 31 to the positive-phase input of the operational amplifier. The output of the operational amplifier 34 is composed of ten N-channel MOS transistors Tr3 whose gates and drains are connected in parallel.
Input to the gates of a to Tr3j.

Each Nch type MOS transistor Tr3a-
The drain of Tr3j is connected to the load terminal 32. Further, Nch type MOS transistors Tr3a to Tr3
Current detection resistors R9a to R9j are connected to the respective sources of 3j. The other ends of the current detection resistors R9a to R9j are grounded via a ground terminal 33. Current detection resistor R9
a to R9j and the ground, wiring resistances R10a to R10
10j are present. Nch type MOS transistor Tr3
The source of a is connected to the negative-phase input of the operational amplifier 34 to form a negative feedback loop. Therefore, the circuit operation is performed so that the positive-phase input and the negative-phase input of the operational amplifier 34 are imaginary short-circuited, that is, the positive-phase input and the negative-phase input have the same voltage.

Here, an Nch type MOS transistor Tr
Assuming that the source current of 3a is I3a, the resistance value of the current detection resistor R9a is r9a, the resistance value of the wiring resistor R10a is r10a, the source potential of the Nch-type MOS transistor Tr3a is V6, and the ground potential of the current detection resistor R9a is V7. , Potential V6 and potential V7 can be expressed as follows: V7 = r10a.I3a (1) V6 = (r9a + r10a) .I3a (2)

If an imaginary short is established at the input voltage of the operational amplifier 34 by the negative feedback operation, then Vi ′ = V6 (3). Therefore, from the expressions (2) and (3), Vi ′ = (r9a + r10a) · I3a (4)

In equation (4), the resistance value r9a of the current detection resistor R9a is often much larger than the resistance value r10a of the wiring resistor R10a, and can be regarded as r10a << r9a, so that the Nch type MOS transistor Tr3a Current I3a flowing through the circuit and the control signal voltage V
The relationship with i ′ is I3a ≒ Vi ′ / r9a (5), and the source current I3a according to the control signal voltage Vi ′
It turns out that flows.

[0007] Ten Nch type MOS transistors Tr
The source currents of 3a to Tr3j are I3a, I3b.
3j, where the total source current is I3-all (A), the resistance values of the resistors R9a to R9j are, for example, r9a = r9
= r9j = 0.1 (Ω) and the input / output characteristics of the Nch-type MOS transistors Tr3a to Tr3j can be regarded as being equal to each other: I3a = I3b... = I3j = Vi ′ / 0. 1 Becomes

Another example is a discharge type constant current circuit shown in FIG. In this constant current circuit, a constant current corresponding to the control signal voltage Vi ′ input from the control input terminal 41 is output to the load terminal 42 based on the power supply voltage Vd applied to the power supply terminal 43. First, the control signal voltage Vi ′ is input from the control input terminal 41 to the in-phase input of the operational amplifier 44. The output of the operational amplifier 44 is input to the gates of ten P-channel MOS transistors Tr4a to Tr4j whose gates and drains are connected in parallel.

Each Pch type MOS transistor Tr4a-
The drain of Tr4j is connected to the load terminal 42. Further, Pch type MOS transistors Tr4a to Tr4
4j have current detection resistors R11a to R11j.
Is connected. The other ends of the current detection resistors R11a to R11j are connected to a power supply terminal 44. Current detection resistor R
11a to R11j and the power supply, a wiring resistance R12
a to R12j. The source of the P-channel MOS transistor Tr4a is connected to the negative-phase input of the operational amplifier 44 to form a negative feedback loop, and the circuit operation is performed so that the positive-phase input and the negative-phase input of the operational amplifier 44 are imaginary short-circuited.

Here, the Pch type MOS transistor Tr
The source current of 4a is I4a, the resistance value of the current detection resistor R11a is r11a, and the resistance value of the wiring resistor R12a is r12.
a, the source potential of the Pch type MOS transistor Tr4a is V6 ′, and the power supply side potential of the current detection resistor R11a is V7 ′.
Then, the potentials V6 ′ and V7 ′ can be expressed as follows: V7 ′ = Vd− (r12a · I4a) (6) V6 ′ = Vd− (r11a + r12a) · I4a (7)

If an imaginary short is established at the input voltage of the operational amplifier 44 by the negative feedback operation, then Vi '= V6' (8). Therefore, from the equations (7) and (8), Vi ′ = Vd− (r11a + r12a) · I4a (9)

In equation (9), the current detection resistor R11a
Is the resistance value r12a of the wiring resistance R12a.
R12a << r11a, so that the source current I4a flowing through the P-channel MOS transistor Tr4a and the control signal voltage V
The relationship with i ′ is I4a ≒ (Vd−Vi ′) / r11a (10), and the control signal voltage V
It can be seen that the source current I4a according to i ′ flows.

[0013] Ten Pch type MOS transistors Tr
4a to Tr4j are set to I4a, I4b.
4j and the total source current is I4-all (A), the resistance values of the resistors R11a to R11j are, for example, r11
a = r11b... = r11j = 0.1 (Ω)
Further, if the input / output characteristics of the Pch type MOS transistors Tr4a to Tr4j can be regarded as being equal, I4a = I4b... = I4j = (Vd−Vi ′) /
0.1, and I4-all (A) = 10 · {(Vd−Vi ′) / 0.1} = 100 · (Vd−Vi ′).

[0014]

However, the conventional constant current circuit does not consider the operation when the input / output characteristics of the control transistor vary. The operation of the conventional suction-type constant current circuit shown in FIG. 4 when there is a variation in the input / output characteristics of the control transistor will be described. From the equation (5), the relationship between the source current I3a flowing through the Nch-type MOS transistor Tr3a and the control signal voltage Vi ′ is as follows: Vi ′ = r9a · I3a, and the source current I3a according to the control signal voltage Vi ′
Flows into the N-channel MOS transistor Tr3a.

At this time, the N-channel MOS transistor T
Assuming that the gate-source voltage of r3a is Vgs1, Vgs1 is also applied between the gate and source of each of the N-channel MOS transistors Tr3b to Tr3j. MO
The S transistor uses a gate-source voltage as a main control factor, and normally flows a current between the drain and source according to the gate-source voltage. However, even if the gate-source voltage Vgs1 that generates the source current is equal, if there is a variation in the input / output characteristics of each of the N-channel MOS transistors Tr3a to Tr3j, the same source current is not obtained. ≠ I3b... ≠ I3j.

In this case, ten Nch-type M
If the total source current of the OS transistors Tr3a to Tr3j is I3-all (A), I3-all is And the output current value is not uniquely determined by the control signal voltage. The same operation is performed in the conventional discharge type constant current circuit shown in FIG.

In the conventional constant current circuit, Nc
Since the resistance value of the current detection resistor connected to the source of the h-type MOS transistor or the Pch type MOS transistor is set to a value larger than the resistance value of the wiring resistance on the source side, the resistance value of the wiring resistance << current Since it can be regarded as the resistance value of the detection resistor, the resistance value of the wiring resistance rarely affected the control operation. However, in a circuit whose output current has been increased in capacity, which has been developed in recent years, a large amount of current flows through the current detection resistor.
If a current detection resistor having a large resistance value is used, normal circuit operation may not be performed.

That is, since the power loss at the resistor is (current value) ² · resistance value, if the resistance value of the current detection resistor is increased, self-heating at the current detection resistor becomes remarkable,
This is because the operating temperature may exceed the allowable range. Therefore, in a constant current circuit provided in a large-capacity circuit, it is difficult to set the resistance value of the current detection resistor to a value sufficiently larger than the resistance value of the wiring resistance.

In the conventional suction-type constant current circuit shown in FIG. 4, when the resistance value of the current detection resistor is set to a relatively small value, the resistance value of the wiring resistance << the resistance value of the current detection resistor can be regarded. Disappears. The operation in this case will be described. In equation (5), it cannot be considered that r10a << r9a, so that the Nch-type MOS transistor Tr
From equation (4), the source current I3a flowing through 3 can be expressed as I3a = Vi ′ / (r9a + r10a).

The resistance values of the wiring resistances R10a to R10j between the current detection resistors R9a to R9j and the ground are represented by r10a to r1.
0j, each of the N-type control transistors Tr3b to Tr3b
The source currents I3b to I3j of 3j are as follows: I3b = Vi '/ (r9b + r10b) I3c = Vi' / (r9c + r10c) I3j = Vi '/ (r9j + r10j)

Normally, since the wiring distance between each of the current detection resistors R9a to R9j and the ground is not the same, the wiring resistance R10a
R10j have different values from each other. Therefore, even if the resistance values r9a to r9j of the current detection resistors R9a to R9j are the same, the Nch type M
Source current I3 of OS transistors Tr3a to Tr3j
a to I3j are I3a ≠ I3b... ≠ I3j, and the current flowing through each Nch-type MOS transistor varies. Also, 10 Nch type MOS
The total source current of the transistors Tr3a to Tr3j is I
If 3-all (A), I3-all is not uniquely determined by the control signal voltage. The same operation is performed in the conventional discharge type constant current circuit shown in FIG.

That is, when a conventional constant current circuit in which the resistance value of the current detection resistor is set to a small value is used for an application requiring a large current, the resistance of the source wiring of the Nch-type transistor or the Pch-type transistor as the control transistor is reduced. Will result in non-negligible gate-source voltage variations. For example, when the variation in the wiring resistance is 0.05
(Ω) and Vgs1 even when the source current is 10 (A).
Will vary by 0.5 (V).

When a constant current circuit is provided in a circuit operated with a large capacity, an Nch transistor or Pc
h-type transistors are often operated near their maximum ratings. For this reason, if there is variation in the current values flowing through the individual control transistors, the control transistors that vary so that the current value increases may exceed the maximum junction temperature or the maximum drain current specification, and may cause unstable operation. There were also problems.

In view of the above-mentioned conventional problems, the present invention operates stably even when there is a variation in the resistance value of the wiring resistance or a variation in the input / output characteristics of the control transistor. It is an object of the present invention to provide a constant current circuit that can supply a constant current according to a voltage and has improved reliability.

[0025]

In order to solve the above-mentioned problems, the invention according to claim 1 includes a plurality of modules, and in each of the modules, an input terminal is connected to a positive-phase input of an operational amplifier. The output of the operational amplifier is connected to the gate of the N-type control transistor, the drain of the N-type control transistor is connected to the output terminal, and the source is connected to one end of the current detection resistor and the positive-phase input of the differential amplifier. The other end of the resistor is connected to the negative-phase input of the differential amplifier and the ground terminal, the reference voltage input of the differential amplifier is connected to the ground-side input terminal, and the output of the differential amplifier is the negative-phase input of the operational amplifier. The input terminals of each module are connected in parallel and connected to the control input terminal, the output terminals of each module are connected in parallel and connected to the load terminal, and the ground terminal and ground side input terminal of each module are connected It was constructed as is the earth.

According to a second aspect of the present invention, a plurality of modules are provided, and in each module, an input terminal is connected to a negative-phase input of an operational amplifier, and an output of the operational amplifier is connected to a gate of an N-type control transistor. The drain of the N-type control transistor is connected to the output terminal, the source is connected to one end of the current detection resistor and the negative-phase input of the differential amplifier,
The other end of the current detection resistor is connected to the positive-phase input of the differential amplifier and the ground terminal, the reference voltage input of the differential amplifier is connected to the ground-side input terminal, and the output of the differential amplifier is connected to the positive terminal of the operational amplifier. Connected to the phase input, the input terminal of each module is connected in parallel and connected to the control input terminal, the output terminal of each module is connected in parallel and connected to the load terminal, and the ground terminal and ground side input terminal of each module are connected It was configured to be grounded.

According to a third aspect of the present invention, a plurality of modules are provided. In each module, an input terminal is connected to a positive-phase input of an operational amplifier, and an output of the operational amplifier is connected to a gate of a P-type control transistor. The drain of the P-type control transistor is connected to the output terminal, the source is connected to one end of the current detection resistor and the negative-phase input of the differential amplifier,
The other end of the current detection resistor is connected to the positive-phase input and the power supply terminal of the differential amplifier, the reference voltage input of the differential amplifier is connected to the ground-side input terminal, and the output of the differential amplifier is connected to the negative phase of the operational amplifier. Connect to input, input terminal of each module is connected in parallel and connected to control input terminal, output terminal of each module is connected in parallel and connected to load terminal, power terminal of each module is connected to power supply, ground The side input terminal was configured to be grounded.

According to a fourth aspect of the present invention, there are provided a plurality of modules, wherein in each module, an input terminal is connected to a negative-phase input of an operational amplifier, and an output of the operational amplifier is connected to a gate of a P-type control transistor. , The drain of the P-type control transistor is connected to the output terminal, the source is connected to one end of the current detection resistor and the positive-phase input of the differential amplifier, and the other end of the current detection resistor is connected to the negative-phase input of the differential amplifier. Connect to the power supply terminal, connect the reference voltage input of the differential amplifier to the ground-side input terminal, connect the output of the differential amplifier to the positive-phase input of the operational amplifier, and connect the input terminals of each module in parallel to control The input terminals were connected, the output terminals of each module were connected in parallel and connected to a load terminal, the power supply terminal of each module was connected to a power supply, and the ground input terminal was configured to be grounded.

According to a fifth aspect of the present invention, the N-type control transistor is an NPN bipolar transistor,
The channel type MOS transistor or Nch IGBT was used. In the invention according to claim 6, the P-type control transistor is a PNP bipolar transistor,
It is assumed to be a ch-type MOS transistor or a PchIGBT.

According to a seventh aspect of the present invention, the differential amplifier includes a second operational amplifier, and a positive input terminal of the differential amplifier is connected to a positive input of the second operational amplifier via the first resistor. And a reference voltage input terminal of the differential amplifier is connected to a positive-phase input of a second operational amplifier via a second resistor, and a negative-phase input terminal of the differential amplifier is connected to a second operational amplifier via a third resistor. The output of the differential amplifier is connected to the output terminal of the second operational amplifier and one end of a fourth resistor, and the other end of the fourth resistor is connected to the opposite terminal of the second operational amplifier. It is assumed that it is connected to the phase input.

In a preferred embodiment of the present invention, the differential amplifier includes third, fourth, and fifth operational amplifiers, and a positive-phase input terminal of the differential amplifier has a positive-phase input of the third operational amplifier. And the opposite-phase input terminal of the differential amplifier is connected to a fourth
And the negative-phase input of the third operational amplifier and the negative-phase input of the fourth operational amplifier are connected via a fifth resistor, and the third operational amplifier Are connected via a sixth resistor, the negative-phase input and output of the fourth operational amplifier are connected via a seventh resistor, and the positive-phase input of the fifth operational amplifier is connected. , The output of the third operational amplifier is input via an eighth resistor, the reference voltage input terminal is input via a ninth resistor, and the negative-phase input of the fifth operational amplifier is , The output of the fourth operational amplifier is input via a tenth resistor, and the negative-phase input and output of the fifth operational amplifier are connected via an eleventh resistor.

[0032]

According to the first aspect of the present invention, in each module, the input terminal is connected to the in-phase input of the operational amplifier, and the output of the operational amplifier is connected to the gate of the N-type control transistor. Of the current detection resistor, one end of the current detection resistor connected to the source of the N-type control transistor is connected to the positive-phase input of the differential amplifier, and the other end is connected to the negative-phase input. By connecting the output of the amplifier to the negative-phase input of the operational amplifier, the operational amplifier is negatively fed back by the current detection resistor.

The source current of the N-type control transistor is determined by the negative feedback, the control signal voltage input to the positive-phase input of the operational amplifier, the amplification factor of the differential amplifier, and the resistance value of the current detection resistor. It is not affected by the resistance value of the wiring resistance existing between one end of the detection resistor and the ground. Therefore, even if there is a variation in the resistance value of the wiring resistance on the source side of the N-type control transistor provided in each module, no variation occurs in the source current of each N-type control transistor.

Further, since each N-type control transistor is subjected to individual negative feedback to form a closed loop circuit, even if the input / output characteristics of each N-type control transistor vary, the negative feedback operation is performed. As a result, the control characteristics are kept constant, so that variations in the input / output characteristics of the N-type control transistor are absorbed, and no variations occur in the source current of the N-type control transistor. As a result, the N-type control transistor does not exceed the maximum junction temperature or the maximum drain current specification even when operating near the maximum rating. Therefore, even if there is a variation in the wiring resistance or a variation in the input / output characteristics of the control transistor, a stable constant-current circuit that operates stably and can supply a constant current according to the control signal voltage is provided. realizable.

According to a second aspect of the present invention, in each module, the input terminal is connected to the negative-phase input of the operational amplifier, and the output of the operational amplifier is connected to the gate of the N-type control transistor. Of the current detection resistor, one end of the current detection resistor connected to the source of the N-type control transistor is connected to the negative-phase input of the differential amplifier, and the other end is connected to the positive-phase input. By connecting the output of the amplifier to the positive-phase input of the operational amplifier, the operational amplifier is negatively fed back by the current detection resistor.

The source current of the N-type control transistor is determined by the negative feedback, the control signal voltage input to the negative-phase input of the operational amplifier, the amplification factor of the differential amplifier, and the resistance value of the current detection resistor. It is not affected by the resistance value of the wiring resistance existing between one end of the detection resistor and the ground. For this reason, even if there is variation in the wiring resistance on the source side of the N-type control transistor provided in each module, there is no variation in the source current of the N-type control transistor.

Further, since each negative feedback is applied to each N-type control transistor to form a closed loop circuit, even if the input / output characteristics of the N-type control transistor vary, the negative feedback operation is performed. Since the control characteristics are kept constant, variations in the input / output characteristics of the N-type control transistor are absorbed, and no variations occur in the source current of the N-type control transistor. As a result, the N-type control transistor does not exceed the maximum junction temperature or the maximum drain current specification even when operating near the maximum rating. Therefore,
Even if there is a variation in the wiring resistance or a variation in the input / output characteristics of the control transistor, a stable constant current circuit that operates stably and can supply a constant current according to the control signal voltage can be realized. .

Further, in the invention according to claim 3,
In each module, the input terminal is connected to the in-phase input of the operational amplifier, the output of the operational amplifier is connected to the gate of the P-type control transistor, and the source of the P-type control transistor is
Connect the current detection resistor, connect one end of the current detection resistor connected to the source of the P-type control transistor to the negative-phase input of the differential amplifier, connect the other end to the positive-phase input, and connect the output of the differential amplifier. By being connected to the negative-phase input of the operational amplifier, the operational amplifier is subjected to negative feedback by the current detection resistor.

The source current of the P-type control transistor is determined by the negative feedback, the control signal voltage input to the positive-phase input of the operational amplifier, the amplification factor of the differential amplifier, and the resistance value of the current detection resistor. It is not affected by the resistance value of the wiring resistance existing between one end of the detection resistor and the power supply. For this reason, even if there is variation in the wiring resistance on the source side of the P-type control transistor provided in each module, there is no variation in the source current of the P-type control transistor.

Further, since each P-type control transistor is subjected to individual negative feedback to form a closed loop circuit, even if the input / output characteristics of the P-type control transistor vary, the negative feedback operation is performed. Since the control characteristics are kept constant, variations in the input / output characteristics of the P-type control transistor are absorbed, and no variations occur in the source current of the P-type control transistor. As a result, even when operating near the maximum rating, the P-type control transistor does not exceed the maximum junction temperature or the maximum drain current specification. Therefore,
Even if there is a variation in the wiring resistance or a variation in the input / output characteristics of the control transistor, a stable constant current circuit that operates stably and can supply a constant current according to the control signal voltage can be realized. .

According to the fourth aspect of the present invention, in each module, the input terminal is connected to the negative-phase input of the operational amplifier, the output of the operational amplifier is connected to the gate of the P-type control transistor, and the source of the P-type control transistor is connected. , A current detection resistor is connected, one end of the current detection resistor connected to the source of the P-type control transistor is connected to the positive-phase input of the differential amplifier, and the other end is connected to the negative-phase input. By connecting the output to the positive-phase input of the operational amplifier, the operational amplifier is negatively fed back by the current detection resistor.

The source current of the P-type control transistor is determined by the negative feedback, the control signal voltage input to the negative-phase input of the operational amplifier, the amplification factor of the differential amplifier, and the resistance value of the current detection resistor. It is not affected by the resistance value of the wiring resistance existing between one end of the detection resistor and the power supply. For this reason, even if there is variation in the resistance value of the wiring resistance on the source side of the P-type control transistor provided in each module, there is no variation in the source current of each P-type control transistor.

Further, since each P-type control transistor is subjected to individual negative feedback and forms a closed loop circuit, even if the input / output characteristics of each P-type control transistor vary, the negative feedback operation is performed. As a result, the control characteristics are kept constant, so that the variation in the input / output characteristics of the P-type control transistor is absorbed, and the source current of the P-type control transistor does not vary. As a result, even when operating near the maximum rating, the P-type control transistor does not exceed the maximum junction temperature or the maximum drain current specification. Therefore, even if there is a variation in the wiring resistance or a variation in the input / output characteristics of the control transistor, a stable constant-current circuit that operates stably and can supply a constant current according to the control signal voltage is provided. realizable.

Further, in the invention according to claim 7, the positive-phase input terminal of the differential amplifier is connected to the positive-phase input of the second operational amplifier via the first resistor, and the reference voltage input terminal of the differential amplifier is By connecting to the positive-phase input of the second operational amplifier via the second resistor and connecting the negative-phase input terminal of the differential amplifier to the negative-phase input of the second operational amplifier via the third resistor, The difference voltage between the positive-phase input terminal and the negative-phase input terminal of the differential amplifier can be detected with reference to the voltage input to the reference voltage input terminal of the dynamic amplifier.

According to the eighth aspect of the present invention, a signal is input to the positive-phase inputs of the third and fourth operational amplifiers without passing through a resistor, and the negative-phase inputs of the third and fourth operational amplifiers are connected to the first and second operational amplifiers. 5, the input impedance of the signal receiving side becomes the input resistance of the third and fourth operational amplifiers, and becomes a sufficiently large value. Therefore, the impedance of the signal source input to the differential amplifier is increased. Is the normal phase,
Even if the phases are different from each other in the opposite phases, no change occurs in the input signal, and the signal is transmitted to the in-phase inputs of the third and fourth operational amplifiers. Therefore, even if the impedance of the signal source input to the differential amplifier is different between the positive and negative phases, the signal is input without being affected, the common-mode component noise of both inputs is suppressed, and the differential voltage is amplified. it can.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to examples. FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention. FIG. 1A shows an overall configuration diagram, and FIG. 1B shows a circuit configuration of the module shown in FIG. FIG. This embodiment is a suction-type constant current circuit including ten modules 10a to 10j connected in parallel, and supplies a constant current output according to a control signal voltage.

Each of the modules 10a to 10j has the same circuit configuration and includes an input terminal 11, an output terminal 12, a ground terminal 13, and a ground input terminal 14. The input terminals 11 of the modules 10a to 10j are connected in parallel and connected to the control input terminal 1 of the constant current circuit. The output terminal 12 is also connected in parallel, and is connected to the load terminal 2 of the constant current circuit. The ground terminal 13 and the ground-side input terminal 14 are connected in parallel, and are grounded via the ground terminal 3 to a casing (not shown).

As an example of the module, the module 10
The circuit configuration of a is shown in FIG. The input terminal 11 is connected to the positive-phase input of the operational amplifier 15. The ground side input terminal 14 is connected to the reference voltage input terminal 16r of the differential amplifier 16. The output of the operational amplifier 15 is connected to the gate of the Nch type MOS transistor Tr1. Output terminal 12 is N
Connected to the drain of ch-type MOS transistor Tr1. The source of the N-channel MOS transistor Tr1 is connected to the current detection resistor R1 and the positive-phase input terminal 1 of the differential amplifier 16.
6p is connected.

The other end of the current detecting resistor R1 is connected to the negative-phase input terminal 16m of the differential amplifier 16, and is grounded via the ground terminal 13 and the ground terminal 3.
A wiring resistance R2a exists between one end of the current detection resistance R1 and the ground. Since the wiring distance between the current detection resistor and the ground varies depending on the arrangement of each module, wiring resistances R2a to R2j having different resistance values exist in the modules 10a to 10j.

Next, the operation of the module 10a will be briefly described. When the potential of the ground side input terminal 14 is Vr,
A control signal voltage applied between the input terminal 11 and the ground-side input terminal 24 is denoted by Vi. The control signal voltage Vi is input to the positive-phase input of the operational amplifier 15. The output of the operational amplifier 15 is input to the gate of the Nch-type MOS transistor Tr1, and controls the on-resistance of the Nch-type MOS transistor Tr1. If the gate potential is high, the on-resistance of the Nch-type MOS transistor Tr1 decreases, and if the gate potential is low, N
The on-resistance of the channel MOS transistor Tr1 increases.

When a load is connected to the output terminal 12 via the load terminal 2, the Nch type MOS transistor Tr
The output current corresponding to the ON resistance of 1 is output from the output terminal 12 to Nc.
It flows toward the source of the h-type MOS transistor Tr1. A current detection resistor R1 is connected to the source of the Nch type MOS transistor Tr1, and a voltage proportional to the source current is generated at both ends of the current detection resistor R1. The voltage is amplified by the differential amplifier 16 and input to the negative-phase input of the operational amplifier 15 to form a negative feedback loop. Therefore, the circuit operation is performed so that the positive-phase input and the negative-phase input of the operational amplifier 15 have an imaginary short, that is, an equal value.

Before describing the detailed operation of the module 10a, the configuration and operation of the differential amplifier 16 will be described first. The differential amplifier 16 includes an operational amplifier 17, and resistors R3, R4, R5, and R6, as shown in FIG. The positive-phase input of the operational amplifier 17 is connected to a resistor R3
Is connected to the positive-phase input terminal 16p of the differential amplifier 16 via a resistor R4 and to the reference voltage input terminal 16r via a resistor R4.

The negative-phase input of the operational amplifier 17 is connected to the negative-phase input terminal 16m of the differential amplifier 16 via the resistor R5 and to one end of the resistor R6. The output of the operational amplifier 17 is connected to the output terminal 16o of the differential amplifier 16 and the resistor R.
6 is connected to the other end. Note that the operational amplifier 17 constitutes a second operational amplifier of the present invention. The resistor R3 constitutes the first resistor of the invention, the resistor R4 constitutes the second resistor, the resistor R5 constitutes the third resistor, and the resistor R6 constitutes the fourth resistor.

The potential of the positive-phase input terminal 16p of the differential amplifier 16 is V1, the potential of the negative-phase input terminal 16m is V2, the potential of the reference voltage input terminal 16r is Vr, the potential of the output terminal 16o is V3, and the potential of the operational amplifier 17 is The potential of the positive-phase input is V4, the potential of the negative-phase input of the operational amplifier 17 is V5, and the resistors R3 to R6.
Are the resistance values of r3 to r6, the potential V4 and the potential V
5 can be represented as follows: V4 = (r4 · V1 + r3 · Vr) / (r3 + r4) (11) V5 = (r6 · V2 + r5 · V3) / (r5 + r6) (12) Since the operational amplifier 17 is subjected to negative feedback by the resistor R6, the operational amplifier 17 The circuit operation is performed so that the positive-phase input and the negative-phase input of the IGBT become imaginary short-circuit, and the potential V4
Since the potential V5 and the potential V5 become equal, the following equation is established. V4 = V5 (13)

From the equations (11), (12) and (13), the potential V3 is expressed as follows: V3 = {(r4.V1 + r3.Vr). (R5 + r6) / (r3 + r4) -r6.V2} / r5 (14) Can be. Here, if the resistance values r3 to r6 of the resistors R3 to R6 are set so that r3 = r5 and r4 = r6, V3 = (V1−V2) · (r4 / r3) + Vr (15)

If the voltage amplification factor of the differential amplifier 16 at this time is A1, then A1 = ΔV3 / Δ (V1-V2) (16), so that from the equations (15) and (16), A1 = r4 / r3 (17) Therefore, from Expressions (15) and (17), V3 = A1 · (V1−V2) + Vr (18)

In this embodiment, the differential amplifier 16 shown in FIG. 2A is used as the differential amplifier, but the present invention is not limited to this. For example, a differential amplifier 16 'including three operational amplifiers 18a, 18b, and 19 as shown in FIG. 2B can be used.

Differential amplifier 16 'positive-phase input terminal 16p'
Is input to the positive-phase input of the operational amplifier 18a, the negative-phase input terminal 16m 'is input to the positive-phase input of the operational amplifier 18b, and the negative-phase input of the operational amplifier 18a and the negative-phase input of the operational amplifier 18b are connected in resistance. R1 ', the opposite-phase input and output of the operational amplifier 18a are connected via a resistor R2', and the negative-phase input and output of the operational amplifier 18b are connected via a resistor R3 '. The output of the operational amplifier 18a is input to the positive-phase input via a resistor R4 ', the reference voltage input terminal 16r' is input via a resistor R6 ', and the negative-phase input of the operational amplifier 19 is The output of the amplifier 18b is input via a resistor R5 ', and the negative-phase input and output of the operational amplifier 19 are connected via a resistor R7'.

According to the above configuration, a signal is input to the positive-phase inputs of the operational amplifiers 18a and 18b without using a resistor, and the negative-phase inputs of the operational amplifiers 18a and 18b are connected by the resistor R1 '. By
The input impedance of the signal receiving side becomes the input resistance of the operational amplifiers 18a and 18b and becomes a sufficiently large value. Therefore, the impedance of the signal source input to the differential amplifier 16 ′ differs between the positive and negative phases. Even
No change occurs in the input signal, and the operational amplifier 18a
And to the non-inverting input of the operational amplifier 18b. Therefore, even if the impedance of the signal source input to the differential amplifier 16 'is different between the positive and negative phases, the signal is input without being affected, the common mode component noise of both input signals is suppressed, and the differential The voltage is amplified.

Next, the operation of the module 10a will be described in detail. The source current of the Nch-type MOS transistor Tr1 is defined as I1a, and the resistance value of the current detection resistor R1 is defined as r1. The resistance value of the wiring resistance R2a from one end of the current detection resistance R1 to the ground is defined as r2a.

The potential V2 of the negative-phase input terminal 16m of the differential amplifier 16 is also the ground potential of the current detecting resistor R1, and can be expressed as follows. V2 = r2a · I1a (19) The potential V1 of the positive-phase input terminal 16p of the differential amplifier 16
Is also the source potential of the Nch type MOS transistor Tr1, and can be expressed as follows. V1 = (r1 + r2a) · I1a (20)

Further, the potential V3 of the output terminal 16o of the differential amplifier 16 is obtained from the equations (19) and (20) and the equation (18) described in the description of the differential amplifier 16 as follows. A1 · r1 · I1a + Vr (21) Since the ground-side input terminal 14 is grounded to the housing, the potential Vr can be regarded as Vr = 0, and the equation (21) can be expressed as follows. V3 = A1 · r1 · I1a (22)

Since the operational amplifier 15 is negatively fed back by the current detection resistor R1, the circuit operation is performed so that the positive-phase input and the negative-phase input of the operational amplifier 15 are imaginarily short-circuited, and the potential Vi and the potential V3 Are equal, the following equation holds. Vi = V3 (23) From equation (22) and equation (23), Vi = A1 · r1 · I1a (24) Therefore, I1a = Vi / A1 · r1 (25) From equation (25), the source current I1a of the Nch-type MOS transistor Tr1 is not affected by the wiring resistance r2a, and is dependent on the control signal voltage Vi, the amplification factor A1 of the differential amplifier 16, and the resistance value of the current detection resistor R1. It can be seen that it is determined by r1.

The operation of the suction type constant current circuit is as follows. The load current drawn from the load terminal 2 is shunted to the output terminals 12 of the modules 10a to 10j, and is grounded at the ground terminal 3 via the ground terminal 13. Is done. In each of the modules 10a to 10j, the source current is determined by the control signal voltage Vi, the amplification factor A1 of the differential amplifier 16, and the resistance value r1 of the current detection resistor R1.
1 and the resistance values r2a to r2a of the wiring resistances R2a to R2j.
It is not affected by r2j. That is, each module 10a-1
0j, the resistance value r2a of the wiring resistances R2a to R2j.
Even if there is a variation in the values of .about.r2j, the current value shunted to each module is not affected by the variation in the wiring resistance value.

Further, since each Nch-type MOS transistor is subjected to individual negative feedback to form a closed loop circuit, even if the input / output characteristics of the Nch-type MOS transistor vary, the negative feedback operation is performed. Since the control characteristics are kept constant, variations in the input / output characteristics of the Nch-type MOS transistor are absorbed. That is, it is not affected by variations in the input / output characteristics of the Nch type MOS transistor.

Therefore, when the voltage amplification factor A1 of the differential amplifier in each module is equal to the current detection resistance value r1, the load current of the suction type constant current circuit is I-all, and the load current of each of the modules 10a to 10j is Source current is I1a ~
If I1j, the source currents I1a to I1j can be regarded as output currents.
The following equation holds regardless of the variation in the input / output characteristics of the type MOS transistor. I-all = Σ (I1a, I1b,..., I1j) (26) I1a = I1b =... = I1j (27)

Since the voltage amplification factor of the differential amplifier is generally determined by the accuracy of the resistance ratio, it is easy to achieve a variation of less than 1%. Normally, the value is less than about 2%, so that the expressions (26) and (27) are satisfied within the range.

By the above operation, each module 1
0a to 10j Nch MOS transistors Tr1a to Tr1a
The source currents I1a to I1j of Tr1j are determined by negative feedback by the control signal voltage Vi input to the positive-phase input of the operational amplifier 15, the amplification factor A1 of the differential amplifier 16, and the resistance value r1 of the current detection resistor R1. , The current detection resistor R
1 to the ground resistance R2a.
It is not affected by the resistance values r2a to r2j of R2j. Therefore, the resistance values r2a to r2j of the wiring resistances R2a to R2j
Module 10a to 10j
No variation occurs in the source currents I1a to I1j of the Nch-type MOS transistors Tr1a to Tr1j.

Further, since each of the Nch-type MOS transistors Tr1a to Tr1j of each module is subjected to individual negative feedback to form a closed loop circuit,
Even if there are variations in the input / output characteristics of the S transistors Tr1a to Tr1j, the control characteristics are kept constant by the negative feedback operation.
Variations in the input / output characteristics of Tr1j are absorbed, and no variations occur in the source currents I1a to I1j.

As a result, even when operating near the maximum rating, the Nch type MOS transistors Tr1a to Tr1j do not exceed the maximum junction temperature or the maximum drain current specification. Therefore, there is a variation in wiring resistance,
Even if there are variations in the input / output characteristics of the control transistor, a constant current circuit that operates stably and can supply a constant current according to the control signal voltage and has improved reliability can be realized.

The reference potential of the control signal voltage Vi input to the input terminal 11 of each of the modules 10a to 10j via the control input terminal 1 is the potential Vr input to the ground-side input terminal 14. The ground-side input terminals 14a to 10j are grounded to the housing.

For this reason, a large current flows through the Nch type MOS transistors Tr1a to Tr1j of each of the modules 10a to 10j, and a potential rise occurs due to the wiring resistance from the ground terminal 13 to the ground. Even when the potential does not become equal to the case potential, a large current does not flow through the ground-side input terminal 14, so that the potential of the ground-side input terminal 14 is maintained at the case potential. Therefore, the control signal voltage Vi input to the control input terminal 1 is not affected by the rise in the potential of the ground terminal 13, and a normal signal is always input.

In this embodiment, the N-type MOS transistor is used as the N-type control transistor. However, the present invention is not limited to this. For example, an NPN bipolar transistor or an Nch IGBT can be used. Further, in the present embodiment, the control signal voltage Vi is input to the positive-phase input of the operational amplifier 15, and the output of the differential amplifier 16 is input to the negative-phase input of the operational amplifier 15.
The control signal voltage Vi is input to the negative-phase input of the operational amplifier 15, and one end on the source side of the current detection resistor R1 is connected to the differential amplifier 1
6, the other end of the current detection resistor R1 is connected to the positive-phase input of the differential amplifier 16, and the output of the differential amplifier 16 is connected to the positive-phase input of the operational amplifier 15. An effect similar to that of the present embodiment can be obtained.

Next, a description will be given of a second embodiment which is a discharge type constant current circuit. FIG. 3 is a diagram showing the configuration of the second embodiment, and FIG.
FIG. 3B is a diagram showing a circuit configuration of the module shown in FIG. In the present embodiment, 10 parallel-connected
It is a discharge type constant current circuit composed of a plurality of modules 20a to 20j, and supplies a constant current output according to a control signal voltage.

Each of the modules 20a to 20j has the same circuit configuration and includes an input terminal 21, an output terminal 22, a power supply terminal 23, and a ground-side input terminal 24. The input terminals 21 of the modules 20a to 20j are connected in parallel and connected to the control input terminal 4 of the constant current circuit. The output terminal 22 is also connected in parallel, and is connected to the load terminal 5 of the constant current circuit. The power terminal 23 is also connected in parallel,
It is connected to the power supply terminal 6 of the constant current circuit. The ground-side input terminal 24 is grounded via the ground terminal 7 to a housing (not shown).

FIG. 3B shows an example of a module.
2 shows a circuit configuration of a module 20a. Ground side input terminal 2
4 is connected to the reference voltage input terminal of the differential amplifier 16.
The output of the operational amplifier 15 is a Pch type MOS transistor T
Connected to the gate of r2. Output terminal 22 is Pch type M
Connected to the drain of OS transistor Tr2. Pc
The current detection resistor R7 and the negative-phase input terminal of the differential amplifier 16 are connected to the source of the h-type MOS transistor Tr2.

The other end of the current detection resistor R 7 is connected to the positive-phase input terminal of the differential amplifier 16 and the power supply terminal 23. A wiring resistor R8a exists between the current detection resistor R7 and the power supply. Assuming that the wiring resistance between the current detection resistor and the power supply of each of the modules 20a to 20j is R8a to R8j, the wiring distance between the current detection resistance R7 and the power supply differs depending on the arrangement of each module.
The resistance value of j is different.

First, the operation of the module 20a will be briefly described. The potential of the ground-side input terminal 24 is Vr, and the control signal voltage applied between the input terminal 21 and the ground-side input terminal 24 is Vi. The control signal voltage Vi is input to the positive-phase input of the operational amplifier 15. The output of the operational amplifier 15 is
It is input to the gate of the Pch-type MOS transistor Tr2 and controls the on-resistance of the Pch-type MOS transistor Tr2. When the gate potential is low, the on-resistance of the Pch type MOS transistor Tr2 decreases, and when the gate potential is high, Pc
The on-resistance of the h-type MOS transistor Tr2 increases.

When a pull-down load is connected to the output terminal 22 via the load terminal 5, the output current I2a corresponding to the on-resistance of the Pch type MOS transistor Tr2 becomes P
It flows toward the output terminal 22 from the source of the ch-type MOS transistor Tr2. Pch type MOS transistor T
A current detection resistor R7 is connected to the source of r2, and a voltage proportional to the source current is generated at both ends of the current detection resistor R7. The voltage is amplified by the differential amplifier 16 and input to the negative-phase input of the operational amplifier 15 to form a negative feedback loop. Therefore, the circuit operation is performed such that the positive-phase input and the negative-phase input of the operational amplifier 15 are imaginary short-circuited, that is, equal in value.

Next, the operation of the module 20a will be described in more detail. Pch type MOS transistor Tr2
Is the source current of I2a and the resistance value of the current detection resistor R7 is r
7 is assumed. Further, the resistance value of the wiring resistance R8a between the current detection resistor R7 and the power supply is represented by r8a. The power supply side potential of the current detection resistor R7 is set to the potential V2 ', and the Pch type MOS transistor T
Assuming that the source potential of r2 is potential V1 ', V2' = Vd-r8a.I2a (28) V1 '= Vd- (r7 + r8a) .I2a (29)

The potential V at the output terminal of the differential amplifier 16 is
From Equations (28) and (29) and Equation (18) described in the description of the differential amplifier 16 described above, 3 ′ can be expressed as V3 ′ = A1 · r7 · I2a (30) . However, since the potential Vr of the ground side input terminal 24 is grounded, Vr = 0 was set.

Since the operational amplifier 15 is subjected to the negative feedback by the resistor R7, the circuit operation is performed so that the positive-phase input and the negative-phase input of the operational amplifier 15 are imaginarily short-circuited, and the potential Vi and the potential V3 'are changed. Since they are equal, the following equation is established. Vi = V3 '(31) From the equations (30) and (31), Vi = A1.r7.I2a is obtained.

Therefore, I2a = Vi / A1 · r7 (32) From the equation (32), the source current I2a of the Pch-type MOS transistor Tr2 is not affected by the wiring resistance r8a, and the control signal voltage Vi, the amplification factor A1 of the differential amplifier 16, and the resistance value of the current detection resistor R7. It can be seen that it is determined by r7.

The operation of the discharge type constant current circuit is as follows. The current drawn from the power supply terminal 6 is shunted to the power supply terminal 23 of each of the modules 20a to 20j, and from the load terminal 5 to the load via the output terminal 22. Output as load current. In each of the modules 20a to 20j, the source current is determined by the control signal voltage Vi, the amplification factor A1 of the differential amplifier 16 and the resistance value r7 of the current detection resistor R7, and the wiring resistance from one end of the current detection resistor R7 to the power supply. It is not affected by the resistance values r8a to r8j of R8a to R8j.

Further, since each Pch-type MOS transistor is subjected to individual negative feedback to form a closed loop circuit, even if the input / output characteristics of the Pch-type MOS transistor vary, the negative feedback operation is performed. Since the control characteristics are kept constant, variations in the Pch type MOS transistor are absorbed. Therefore, when the voltage amplification factor A1 of the differential amplifier in each module is equal to the current detection resistance value r7, the load current of the discharge type constant current circuit is equal to I2-
all, assuming that the source currents of the individual modules 20a to 20j are I2a to I2j, the source currents I2a to I2j
Can be regarded as an output current, so that the following equation is satisfied irrespective of the variation in the wiring resistance and the variation in the input / output characteristics of the Pch type MOS transistor. I2-all = Σ (I2a, I2b,..., I2j) I2a = I2b =... = I2j

With the above operation, the source currents I2a to I2j of the Pch type MOS transistors Tr2a to Tr2j of each module are, due to the negative feedback, the control signal voltage Vi input to the positive phase input of the operational amplifier and the differential current. It is determined by the amplification factor A1 of the amplifier and the resistance value r7 of the current detection resistor, and is not affected by the resistance values r8a to r8j of the wiring resistors R8a to R8j existing between one end of the current detection resistor and the power supply. Therefore, even if the resistance values r8a to r8j of the wiring resistances R8a to R8j vary, the Pch type MOS transistors Tr2a to Tr2j of each module can be used.
Of the source currents I2a to I2j.

Further, individual negative feedback is applied to the Pch type MOS transistors Tr2a to Tr2j of each module to form a closed loop circuit.
Even if the input / output characteristics of the S transistors Tr2a to Tr2 vary, the control characteristics are kept constant by the negative feedback operation, so that the P-channel MOS transistors Tr2a to Tr2T
Variations in the input / output characteristics of r2j are absorbed, and no variations occur in the source currents I2a to I2j.

As a result, even when operating near the maximum rating, the P-channel MOS transistors Tr2a to Tr2j do not exceed the maximum junction temperature or the maximum drain current specification. Therefore, there is a variation in wiring resistance,
Pch type MOS transistor T which is a control transistor
Even if the input / output characteristics of r2a to Tr2j vary, it is possible to realize a constant current circuit that operates stably and can supply a constant current according to the control signal voltage and has improved reliability.

Note that as the P-type control transistor,
In this embodiment, a Pch type MOS transistor is used. However, the present invention is not limited to this. For example, a PNP bipolar transistor or a Pch IGBT can be used. Further, in the present embodiment, the control signal voltage Vi is input to the positive-phase input of the operational amplifier 15, and the output of the differential amplifier 16 is input to the negative-phase input of the operational amplifier 15.
The control signal voltage Vi is input to the negative-phase input of the operational amplifier 15, and one end of the current detection resistor R7 on the source side is connected to the differential amplifier 1
6, the other end of the current detection resistor R7 is connected to the negative input of the differential amplifier 16, and the output of the differential amplifier 16 is connected to the positive input of the operational amplifier 15. An effect similar to that of the present embodiment can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a circuit diagram showing a circuit of a differential amplifier.

FIG. 3 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional example.

FIG. 5 is a diagram showing a configuration of a conventional example.

[Explanation of symbols]

1, 4, 31, 41 Control input terminal 2, 5, 32, 42 Load terminal 3, 7, 13, 33 Ground terminal 6, 23, 43 Power supply terminal 10a to 10j Module 11, 21 Input terminal 12, 22 Output terminal 14 , 24 Ground side input terminal 15, 17, 18a, 18b, 19, 34, 44 Operational amplifier 16, 16 'Differential amplifier 16m, 16m' Negative phase input terminal of differential amplifier 16o, 16o 'Output terminal of differential amplifier 16p, 16p 'Positive phase input terminal of differential amplifier 16r, 16r' Reference voltage input terminal of differential amplifier 20a-20j Module R1, R7 Current detection resistor R2a-R2j, R8a-R8j Wiring resistance R3, R4, R5, R6 Resistance R1 ', R2', R3 ', R4', R5'R6 ', R
7 'resistance R9a to R9j, R11a to R11j current detection resistance R10a to R10j, R12a to R12j wiring resistance Tr1, Tr3a to Tr3j Nch type MOS transistor Tr2, Tr4a to Tr4j Pch type MOS transistor

Claims (8)

[Claims] A plurality of modules, each module having an input terminal connected to a positive-phase input of an operational amplifier;
The output of the operational amplifier is connected to the gate of the N-type control transistor, the drain of the N-type control transistor is connected to the output terminal, the source is connected to one end of the current detection resistor and the positive-phase input of the differential amplifier, The other end of the current detection resistor is connected to the negative-phase input of the differential amplifier and a ground terminal, the reference voltage input of the differential amplifier is connected to a ground-side input terminal, and the output of the differential amplifier is The input terminals of each module are connected in parallel and connected to a control input terminal, the output terminals of each module are connected in parallel and connected to a load terminal, and the ground terminal of each module is connected. And a ground-side input terminal is grounded. 2. An apparatus comprising: a plurality of modules, wherein each module has an input terminal connected to a negative-phase input of an operational amplifier;
The output of the operational amplifier is connected to the gate of an N-type control transistor, the drain of the N-type control transistor is connected to the output terminal, the source is connected to one end of the current detection resistor and the negative-phase input of the differential amplifier, The other end of the current detection resistor is connected to a positive-phase input of the differential amplifier and a ground terminal, a reference voltage input of the differential amplifier is connected to a ground-side input terminal, and an output of the differential amplifier is Connected to the in-phase input of the amplifier, the input terminals of each module are connected in parallel and connected to a control input terminal, the output terminals of each module are connected in parallel and connected to a load terminal, and the ground terminal of each module And a ground-side input terminal is grounded. A plurality of modules, each module having an input terminal connected to a positive-phase input of an operational amplifier;
The output of the operational amplifier is connected to the gate of a P-type control transistor, the drain of the P-type control transistor is connected to the output terminal, the source is connected to one end of the current detection resistor and the negative-phase input of the differential amplifier, The other end of the current detection resistor is connected to a positive-phase input and a power supply terminal of the differential amplifier, a reference voltage input of the differential amplifier is connected to a ground-side input terminal, and an output of the differential amplifier is The input terminals of each module are connected in parallel and connected to a control input terminal, and the output terminals of each module are connected in parallel and connected to a load terminal. Is connected to a power supply, and a ground-side input terminal is grounded. 4. An apparatus comprising: a plurality of modules, wherein each module has an input terminal connected to a negative-phase input of an operational amplifier;
The output of the operational amplifier is connected to the gate of a P-type control transistor, the drain of the P-type control transistor is connected to an output terminal, the source is connected to one end of a current detection resistor and the positive-phase input of a differential amplifier, The other end of the current detection resistor is connected to the negative-phase input of the differential amplifier and a power supply terminal, the reference voltage input of the differential amplifier is connected to a ground input terminal, and the output of the differential amplifier is The input terminals of each module are connected in parallel and connected to a control input terminal, the output terminals of each module are connected in parallel and connected to a load terminal, and the power terminals of each module are connected. Is connected to a power supply, and a ground-side input terminal is grounded. 5. The constant current circuit according to claim 1, wherein the N-type control transistor is an NPN bipolar transistor, an Nch-type MOS transistor, or an NchIGBT. 6. The constant current circuit according to claim 3, wherein the P-type control transistor is a PNP bipolar transistor, a Pch-type MOS transistor, or a PchIGBT. 7. The differential amplifier includes a second operational amplifier, and a positive-phase input terminal of the differential amplifier is connected to a positive-phase input of a second operational amplifier via a first resistor. Is connected to the positive-phase input of the second operational amplifier via a second resistor, and the negative-phase input terminal of the differential amplifier is connected to the third
And the output terminal of the differential amplifier is connected to the output of the second operational amplifier and one end of a fourth resistor. 5. The constant current circuit according to claim 1, wherein the other end is connected to a negative-phase input of said second operational amplifier. 8. The differential amplifier according to claim 3, wherein said third, fourth and fifth differential amplifiers
Wherein the positive-phase input terminal of the differential amplifier is input to the positive-phase input of a third operational amplifier, and the negative-phase input terminal of the differential amplifier is connected to the positive-phase input terminal of a fourth operational amplifier. And the negative-phase input of the third operational amplifier and the negative-phase input of the fourth operational amplifier are connected via a fifth resistor, and the negative-phase input and output of the third operational amplifier are The fourth operational amplifier is connected via a sixth resistor, the negative-phase input and the output of the fourth operational amplifier are connected via a seventh resistor, and the positive-phase input of the fifth operational amplifier is connected to the third operational amplifier. The output of the operational amplifier is input through an eighth resistor, the reference voltage input terminal is input through a ninth resistor, and the negative-phase input of the fifth operational amplifier is The output of the operational amplifier is input via a tenth resistor, and the negative-phase input and output of the fifth operational amplifier are Constant current circuit of claims 1 to 4, wherein it is connected via a resistor 11.