JP2002268761A - Current generator - Google Patents

Abstract

(57) Abstract: To provide a current generator that can be set to have not only a positive temperature coefficient but also a negative temperature coefficient and temperature-independent characteristics. A constant current i based on a high power supply voltage VCC is provided.
2 and a first power supply voltage V
A current generation circuit includes a voltage circuit 40 that outputs a constant voltage based on CC and a constant current i2, and a second constant current circuit 30 that outputs a constant current io based on a constant voltage output from the voltage circuit 40. Configure the container. Here, the temperature dependency of this current generator is determined by the resistance R3 of the first constant current circuit 20.
And the number n of the diodes D1 to Dn, the resistance of the resistor R2 forming the voltage circuit 40, and the resistance of the resistor R1 forming the second constant current circuit 30. It can be negative or independent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current generator whose temperature dependency can be set arbitrarily.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram of a conventional current generator, which is a basic circuit generally described in an electronic circuit textbook. For example, published by Baifukan, p. R. By Gray,
"Analog Integrated Circuit Design Technology for VLSI", 21
There is a constant current circuit shown on page 8 and the like.

Hereinafter, the configuration and operation of this current generator will be described. The current generator shown in FIG. 3 has a resistor R1 having one end connected to a high power supply voltage terminal 1 to which a high power supply voltage VCC is supplied, a collector terminal connected to the other end and a base terminal of the resistor R1, and an emitter terminal connected to a low potential. N connected to the lower power supply voltage terminal 2 to which the power supply voltage VEE is supplied
A PN transistor Q1, a collector terminal is connected to the output current terminal 3, a base terminal is connected to a base terminal of the NPN transistor Q1, and an emitter terminal is a lower power supply voltage terminal 2.
And an NPN transistor Q0 connected to the power supply.

Here, the difference voltage between the high power supply voltage terminal 1 and the low power supply voltage terminal 2 is Vs, the NPN transistors Q0 and Q1 have the same static characteristics, and the voltage between the base and the emitter is Vbe. It is expressed as The resistance R1
Is a constant value independent of temperature.

[0005] The above conditions, especially the NPN transistor Q
Since 0 and Q1 are the same base-emitter voltage Vbe, the high-level power supply voltage terminal 1 connects the resistors R1, NPN
The current i1 flowing to the lower power supply voltage terminal 2 via the transistor Q1 and the output current io of the output current terminal 3 are NP
It becomes equal by the configuration of a so-called current mirror circuit including N transistors Q0 and Q1, and the following equation (1)
Holds.

(Equation 1)

Here, NPN transistors Q0 and Q
1 is expressed by the following equation (2).
And has a negative temperature coefficient of about −2 mV / ° C. during normal use.

(Equation 2)

Accordingly, the temperature coefficient of the output current io is obtained by the following equation by partially differentiating equation (1) with temperature.

(Equation 3)

From the equation (3), the output current io always has a positive temperature coefficient, and the output current increases as the temperature increases.

[0009]

However, in the above-described conventional current generator, the output current io has a positive temperature coefficient as represented by equation (3), and the temperature coefficient is determined by the resistance value r1 of the resistor R1. Only the size changes.
However, in an actual circuit design, a current generator having a negative temperature coefficient or a temperature-independent characteristic may be required, and there is a problem that a conventional current generator cannot meet such a demand. Was.

The present invention has been made in order to solve the above-mentioned problems. By setting the number of added diodes and the resistance value to arbitrary values, not only the positive temperature coefficient but also the negative temperature coefficient and the temperature can be reduced. It is an object to obtain a current generator which can be set to have an independent characteristic.

[0011]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, in a current generator according to the present invention, a first constant current circuit for generating a first constant current based on a power supply voltage; A voltage circuit that outputs a constant voltage based on the constant voltage; and a second constant current circuit that outputs a second constant current based on the constant voltage.

According to the present invention, the second constant current is equal to the first constant current.
Is generated in accordance with the constant current of the first constant current and the constant voltage determined based on the first constant current. It can depend on the respective characteristic values of the circuit and the voltage circuit.

In the current generator according to the next invention, in the above invention, the voltage circuit is constituted by a first resistor.

According to the present invention, the voltage circuit can be simply constituted by the first resistor, and the specific value can be determined by the resistance value of the first resistor.

In the current generator according to the next invention, in the above invention, the first constant current circuit includes a second resistor having one end supplied with a first power supply voltage, and a second resistor connected to the second resistor.
A first transistor having a collector and a base connected to the other end of the resistor, and a second power supply voltage supplied to the emitter;
A base is connected to the other end of the second resistor, the second power supply voltage is supplied to an emitter, and the first
And a second transistor that outputs a constant current.

According to the present invention, the first transistor and the second transistor constitute a current mirror circuit,
It is possible to generate a first constant current according to a difference voltage between the first power supply voltage and the second power supply voltage and a resistance value of the first resistor.

In the current generator according to the next invention, in the above-mentioned invention, the first constant current circuit is a series connection of one diode or a plurality of diodes each having one end supplied with a first power supply voltage. A first transistor having a collector and a base connected to the other end of the diode or the diode string and having a second power supply voltage supplied to the emitter; and a diode other than the diode or the diode string. The base is connected to the end,
A second transistor having an emitter supplied with the second power supply voltage and outputting the first constant current from a collector;
It is characterized by comprising.

According to this invention, the first transistor and the second transistor form a current mirror circuit,
It is possible to generate a first constant current according to a difference voltage between the first power supply voltage and the second power supply voltage and a forward voltage applied to the diode or the diode string.

[0019] In a current generator according to the next invention, in the above-mentioned invention, the first constant current circuit includes a second constant current circuit.
And a resistor-diode unit configured to be connected in series with one diode or a diode string formed by connecting a plurality of diodes in series, and having a first power supply voltage supplied to one end of the structure. , The resistor-
A first transistor having a collector and a base connected to the other end of the diode unit and a second power supply voltage supplied to the emitter; a base connected to the other end of the resistor-diode unit; and a second transistor connected to the emitter. A second transistor to which a power supply voltage is supplied and which outputs the first constant current from a collector.

According to the present invention, the first transistor and the second transistor form a current mirror circuit,
Generating a first constant current according to a difference voltage between the first power supply voltage and the second power supply voltage, a resistance value of the first resistor, and a forward voltage applied to the diode or the diode string. Can be.

In the current generator according to the next invention, in the above-mentioned invention, the second constant current circuit has a third end to which a constant voltage output from the voltage circuit is supplied to one end.
And a collector and a base connected to the other end of the third resistor and a second power supply voltage supplied to the emitter.
And a fourth transistor having a base connected to the other end of the third resistor, an emitter supplied with the second power supply voltage, and a collector outputting the second constant current. It is characterized by comprising.

According to the present invention, a current mirror circuit is constituted by the third transistor and the fourth transistor,
A second constant current according to the constant voltage output from the voltage circuit and the resistance value of the third resistor can be generated and output.

In the current generator according to the next invention, in the above-mentioned invention, in the second constant current circuit, the first power supply voltage is supplied to a collector, and the second constant current circuit is outputted from the voltage circuit to a base. A third transistor to which a constant voltage is supplied; a third resistor having one end connected to the emitter of the third transistor; a collector and a base connected to the other end of the third resistor; A fourth transistor supplied with a second power supply voltage, a base connected to the other end of the third resistor, the second power supply voltage supplied to an emitter, and the second constant current output from a collector. And a fifth transistor.

According to the invention, the fourth transistor and the fifth transistor form a current mirror circuit,
A base-emitter voltage of the third transistor;
And a second constant current corresponding to the resistance value of the resistor can be generated and output.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the current generator according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited by the embodiment.

Embodiment 1 First, a current generator according to the first embodiment will be described. FIG. 1 is a circuit diagram of the current generator according to the first embodiment. The current generator shown in FIG. 1 includes a first constant current circuit 20 and a second constant current circuit 30.
And a voltage circuit 40.

Here, the voltage circuit 40 is constituted by a resistor R2, and one end of the resistor R2 is connected to the high power supply voltage terminal 1 to which the high power supply voltage VCC is supplied. Also,
The first constant current circuit 20 includes a resistor R3 having one end connected to the higher power supply voltage terminal 1, a diode string having one end connected to the other end of the resistor R3, and a collector terminal connected to the other end of the diode row and a base terminal. An NPN transistor Q3 having an emitter terminal connected to the lower power supply voltage terminal 2 to which the lower power supply voltage VEE is supplied, a collector terminal connected to the other end of the resistor R2, and a base terminal connected to the base terminal of the NPN transistor Q3. And an NPN transistor Q2 having an emitter terminal connected to the lower power supply voltage terminal 2.

The diode row has a structure in which n (n ≧ 1) diodes D1 to Dn are connected in series.
The anode terminal of the first diode D1 is connected to the resistor R3, and the cathode terminal of the last diode Dn is NPN.
Connected to the collector terminal of transistor Q3.

The second constant current circuit 30 has a resistor R1 having one end connected to the other end of the resistor R2, a collector terminal connected to the other end and the base terminal of the resistor R1, and an emitter terminal connected to a low power supply voltage terminal. 2, an NPN transistor Q1, a collector terminal connected to the output current terminal 3, a base terminal connected to the base terminal of the NPN transistor Q1, and an emitter terminal connected to the lower power supply voltage terminal 2.
And N transistor Q0. That is, the second constant current circuit 30 has the same configuration as the conventional current generator shown in FIG. 3 except that one end of the resistor R1 is connected to the other end of the resistor R2.

The operation of the current generator according to the first embodiment will be described below. Here, the high power supply voltage terminal 1
Vs is the difference voltage between the power supply voltage terminal
The transistors Q0, Q1, Q2 and Q3 have the same static characteristics, and their respective base-emitter voltages are
be. The resistance value r1 of the resistor R1 and the resistance R2
It is assumed that the resistance value r2 of the resistor R3 and the resistance value r3 of the resistor R3 are constant values independently of the temperature. Further, the forward voltage of the diodes D1 to Dn is equal to the NPN transistor Q
2 and Q3 equal to the base-emitter voltage, Vb
e.

The above conditions, in particular, the NPN transistor Q
2 and Q3 have the same base-emitter voltage Vbe, the current i3 flowing from the higher power supply voltage terminal 1 to the lower power supply voltage terminal 2 via the resistor R3, the diodes D1 to Dn, the NPN transistor Q3, and the higher power supply voltage The current i2 flowing from the terminal 1 to the lower power supply voltage terminal 2 via the resistor R2 and the NPN transistor Q2 becomes equal due to the configuration of a so-called current mirror circuit composed of the NPN transistors Q2 and Q3, and the following equation (4) holds. .

(Equation 4)

NPN transistors Q0 and Q1
Are the same base-emitter voltage Vbe,
After passing through the resistor R2, the resistor R1 and the NPN transistor Q
1 and the output current io of the output current terminal 3 are equalized by the configuration of a so-called current mirror circuit composed of the NPN transistors Q0 and Q1, and the following equation (5) is obtained. Holds.

(Equation 5)

Here, the NPN transistors Q0, Q1,.
It is assumed that Vbe, which is the base-emitter voltage of Q2 and Q3 and is also the forward voltage of diodes D1 to Dn, has a negative temperature coefficient of about −2 mV / ° C. shown in equation (2). Therefore, the temperature coefficient of the output current io can be obtained by the following equation by partially differentiating equation (5) with temperature.

(Equation 6)

From equation (6), the output current io is (n
+1) Depending on the polarity of r2-r3, it has positive and negative temperature coefficients and temperature independence. For example, (n +
1) If the current generator shown in FIG. 1 is configured by selecting the number n of diodes and the resistance values r2 and r3 so that the relationship of r2> r3 holds, the current generator has a positive temperature coefficient. . Similarly, if the number n of the diodes and the resistance values r2 and r3 are selected so that the relationship of (n + 1) r2 <r3 holds, a negative temperature coefficient is obtained, and (n + 1) r2 = r
The number n of the diodes and the resistance value r so that the relationship of 3 holds.
If 2 and r3 are selected, there is temperature independence.

Also, {(n + 1) r2-r3} / {r3
Depending on the value of (r1 + r2)｝, the absolute value of the temperature coefficient can be set to an arbitrary value. Note that the resistance R1,
The resistance units of R2 and R3 and the number of connections of the diodes D1 to Dn may be configured by a resistor array or a diode unit in which trimming can be selected by zener zapping or laser trimming. In this case, this current generator is
The present invention can be provided as a general-purpose device that can supply a constant current according to the needs of various circuits.

As described above, according to the current generator according to the first embodiment, it is possible to have a desired temperature dependency in accordance with the values of the resistors R1, R2, R3 and the number n of the diodes connected in series. it can.

In the above description, the operation of the current generator using the NPN transistors Q0, Q1, Q2 and Q3 has been described. However, the same operation principle can be applied to a current generator in which these NPN transistors are replaced with PNP transistors. It is clear that a current generator having an arbitrary temperature coefficient can be constructed based on the above equation.

Embodiment 2 Next, a current generator according to the second embodiment will be described. FIG. 2 shows the first embodiment.
FIG. 2 is a circuit diagram of a current generator according to FIG. The current generator shown in FIG. 2 has a collector terminal connected to the higher power supply voltage terminal 1 and a base terminal connected to the other end of the resistor R2.
The current generator according to the first embodiment is different from the current generator according to the first embodiment in that a transistor Q4 is provided and one end of a resistor R1 of a second constant current circuit 30 is connected to an emitter terminal of an NPN transistor Q4. The other configuration is the same as that of FIG. 1. In FIG. 2, parts that are the same as those of FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.

The operation of the current generator according to the second embodiment will be described below. In the description of this operation, as in the first embodiment, the difference voltage between the higher power supply voltage terminal 1 and the lower power supply voltage terminal 2 is Vs, and the NPN transistors Q0, Q1, Q2, Q3, and Q4 are the same. It has static characteristics, and each base-emitter voltage is represented by Vbe. Further, the resistance value r1 of the resistor R1 and the resistance R
It is assumed that the resistance value r2 of R2 and the resistance value r3 of the resistor R3 are constant values independently of the temperature. Further, the forward voltages of the diodes D1 to Dn are equal to the base-emitter voltages of the NPN transistors Q2 and Q3.
be.

Under the conditions described above, first, similarly to the current generator shown in FIG. 1, the current i3 and the current i2 are equal, and the relationship of the above-mentioned equation (4) is established. Further, NPN transistors Q0 and Q1 have the same base-emitter voltage V
be, the NPN from the higher power supply voltage terminal 1
Transistor Q4, resistor R1, NPN transistor Q1
The current i1 flowing to the lower power supply voltage terminal 2 through the NPN transistor Q and the output current io of the output current terminal 3
It becomes equal by the configuration of a so-called current mirror circuit by 0 and Q1, and the relationship of the following equation (7) is established.

(Equation 7)

Here, the NPN transistors Q0, Q1,
Vbe which is the base-emitter voltage of Q2, Q3 and Q4 and the forward voltage of diodes D1 to Dn
Has a negative temperature coefficient of about −2 mV / ° C. shown in equation (2). Therefore, the temperature coefficient of the output current io is
Equation (7) is partially differentiated with respect to temperature and is obtained by the following equation.

(Equation 8)

From this equation (8), the output current io is (n
+1) There are positive and negative temperature coefficients and temperature independence depending on the polarity of r2-2 · r3. For example, (n
+1) If the current generator shown in FIG. 1 is configured by selecting the number n of diodes and the resistance values r2 and r3 such that the relationship of r2> 2 · r3 is satisfied, the current generator has a positive temperature coefficient. Having. Similarly, if the number n of the diodes and the resistance values r2 and r3 are selected so that the relationship of (n + 1) r2 <2 · r3 holds, the temperature coefficient has a negative value, and (n +
1) If the number n of the diodes and the resistance values r2 and r3 are selected so that the relationship of r2 = 2 · r3 holds, there is no temperature dependence.

Also, {(n + 1) r2-2 · r3} / r
The absolute value of the temperature coefficient can be set to an arbitrary value depending on the value of 1 · r3. As described in the first embodiment, each of the resistors R1, R2, and R3 and the number of connections of the diodes D1 to Dn may be configured by a resistor array or a diode unit capable of trimming selection.

As described above, according to the current generator of the second embodiment, the same effects as those of the first embodiment can be enjoyed even with the configuration shown in FIG.

In the above description, the operation of the current generator using the NPN transistors Q0, Q1, Q2, Q3 and Q4 has been described. However, the same applies to a current generator in which these NPN transistors are replaced with PNP transistors. Obviously, based on the principle of operation, a current generator with any temperature coefficient can be constructed.

Also, in the first constant current circuits of the first and second embodiments described above, the order of the series connection of the resistor R3 and the diodes D1 to Dn is shown in FIGS.
May be reversed and is not particularly limited.

[0047]

As described above, according to the present invention, the second constant current is generated according to the first constant current and the constant voltage determined based on the first constant current. , The second constant current as well as the characteristic value of the second constant current circuit,
The characteristic values can be made to depend on the respective characteristic values of the first constant current circuit and the voltage circuit. For example, by selecting these characteristic values to appropriate values, an effect that desired temperature dependency can be obtained can be obtained. Play.

According to the next invention, the voltage circuit can be simply constituted by the first resistor, and the specific value can be determined only by the resistance value of the first resistor.

According to the next invention, a current mirror circuit is constituted by the first transistor and the second transistor, and a difference voltage between the first power supply voltage and the second power supply voltage, and a voltage of the first resistor. It is possible to generate a first constant current according to the resistance value. For example, there is an effect that a current generator having a desired temperature dependency can be formed by the resistance value of the first resistor.

According to the next invention, a current mirror circuit is formed by the first transistor and the second transistor, and a difference voltage between the first power supply voltage and the second power supply voltage is stored in the diode or the diode array. A first constant current corresponding to the applied forward voltage can be generated, for example,
There is an effect that a current generator having a desired temperature dependency can be formed by the forward voltage applied to the diode or the diode array, in other words, the number of diodes.

According to the next invention, a current mirror circuit is formed by the first transistor and the second transistor, and a difference voltage between the first power supply voltage and the second power supply voltage and a voltage of the first resistor are determined. A first constant current can be generated according to the resistance value and the forward voltage applied to the diode or the diode string, for example, the resistance value of the first resistor and the first constant current applied to the diode or the diode string. There is an effect that a current generator having a desired temperature dependency can be constituted by the forward voltage, in other words, the number of diodes.

According to the next invention, a current mirror circuit is constituted by the third transistor and the fourth transistor, and a current mirror circuit corresponding to the constant voltage output from the voltage circuit and the resistance value of the third resistor is provided. Since the constant current of 2 is generated and output,
For example, there is an effect that a current generator having a desired temperature dependency can be configured by the resistance value of the third resistor.

According to the next invention, a current mirror circuit is constituted by the fourth transistor and the fifth transistor, and the base-emitter voltage of the third transistor and
A second constant current corresponding to the resistance value of the third resistor can be generated and output. For example, a current generator having a desired temperature dependency is constituted by the resistance value of the third resistor. It has the effect of being able to do so.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a current generator according to a first embodiment.

FIG. 2 is a circuit diagram of a current generator according to a second embodiment;

FIG. 3 is a circuit diagram of a conventional current generator.

[Explanation of symbols]

1 High power supply voltage terminal, 2 Low power supply voltage terminal, 3 Output current terminal, 20, 30 constant current circuit, 40 voltage circuit, D1-Dn diode, Q0-Q4 NPN transistor, R1, R2, R3 resistor.

Claims (7)

[Claims] A first constant current circuit that generates a first constant current based on a power supply voltage; a voltage circuit that outputs a constant voltage based on the power supply voltage and the first constant current; And a second constant current circuit that outputs a second constant current based on the voltage. 2. The current generator according to claim 1, wherein the voltage circuit includes a first resistor. 3. The first constant current circuit, wherein one end is connected to a second resistor to which a first power supply voltage is supplied, and the other end of the second resistor is connected to a collector and a base.
A first transistor to which a second power supply voltage is supplied to an emitter; a base connected to the other end of the second resistor; a second power supply voltage to be supplied to an emitter;
And a second transistor that outputs the constant current of (i).
The current generator according to claim 1. 4. The first constant current circuit, comprising: a diode string configured by connecting one diode or a plurality of diodes in series with one end supplied with a first power supply voltage; A first transistor having a collector and a base connected to the other end, and a second power supply voltage supplied to an emitter; a base connected to the other end of the diode or the diode string; and a second power supply voltage connected to the emitter. And a second transistor that supplies the first constant current from a collector, and wherein the second transistor outputs the first constant current from a collector.
The current generator according to claim 1. 5. The first constant current circuit includes a series connection of a second resistor and a diode string formed by connecting one diode or a plurality of diodes in series, and one end of the configuration. A first transistor having a collector and a base connected to the other end of the resistor-diode, and a second power supply voltage being supplied to the emitter; A second transistor having a base connected to the other end of the resistor-diode section, the second power supply voltage being supplied to an emitter, and the first constant current being output from a collector. 3. A method according to claim 1, wherein
The current generator according to claim 1. 6. The second constant current circuit, wherein one end of a third resistor to which a constant voltage output from the voltage circuit is supplied, and a collector and a base are connected to the other end of the third resistor. ,
A third transistor having a second power supply voltage supplied to an emitter; a base connected to the other end of the third resistor; a second power supply voltage supplied to an emitter;
The current generator according to any one of claims 1 to 5, further comprising: a fourth transistor that outputs a constant current of: 7. The second constant current circuit, comprising: a third transistor having a collector supplied with a first power supply voltage and a base supplied with a constant voltage output from the voltage circuit; A third resistor having one end connected to the emitter of the transistor, a collector and a base connected to the other end of the third resistor,
A fourth transistor having an emitter supplied with a second power supply voltage; a base connected to the other end of the third resistor; an emitter supplied with the second power supply voltage;
The current generator according to any one of claims 1 to 5, further comprising: a fifth transistor that outputs a constant current of: