JP2008271503A - Reference current circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the temperature dependence of a reference current even in a case where a resistor with an extremely low level of temperature-dependence of a resistance value is employed. <P>SOLUTION: The reference current circuit includes a non-inverting amplifier circuit 110 for receiving a temperature-compensated reference voltage VBG and generating a voltage Vout1 at an output point, and a current source circuit 120 including a current mirror composed of a transistor Q1 connected to the output point of the non-inverting amplifier circuit 110 via a resistor R3 and a transistor Q2 for receiving a voltage equal to a voltage VBE1 generated across terminals of Q 1 and generating a current corresponding to the voltage VBE1. The circuit 110 includes a transistor Q3 a voltage generated across terminals of which has the same temperature characteristic as that of the transistor Q1, and is configured such that the voltage Vout1 is the sum of a temperature-compensated voltage component based on the reference voltage VBG and a voltage component equal to the voltage VBE3 across the terminals of the transistor Q3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reference current circuit that generates a bias current to be supplied to an analog circuit.

FIG. 4 is a diagram showing a configuration of a conventional reference current circuit.
The reference current circuit 400 includes a non-inverting amplifier circuit 410 and a current source circuit 120.
The non-inverting amplifier circuit 410 includes an amplifier circuit OP40 having an inverting input terminal, a non-inverting input terminal, and an output terminal, a resistor R1 inserted in a wiring connecting the inverting input terminal and the ground terminal, an output terminal, and an inverting input. It is comprised from resistance R2 inserted in the wiring which connects a terminal. A reference voltage VBG that does not depend on the temperature T and the power supply voltage Vdd, that is, temperature compensated, is input to the non-inverting input terminal of the amplifier circuit OP40.

The current source circuit 120 includes a resistor R3 whose one terminal is connected to the output terminal of the amplifier circuit OP40, a transistor Q1 whose collector and base are connected to the other terminal of the resistor R3 and whose emitter is grounded, and a collector of the transistor Q1. The transistor Q2 is connected to the base.
In general, a bandgap reference circuit is often used as the reference voltage circuit 500 that outputs the reference voltage VBG, and an example thereof is shown in FIG. The reference voltage circuit 500 includes a resistor R1a connected to the non-inverting input terminal and the output terminal of the amplifier circuit OP5, a transistor Q1a whose emitter is connected to the non-inverting input terminal of the amplifier circuit OP5, and whose base and collector are grounded. A resistor R2a connected between the inverting input terminal and the output terminal of the amplifier circuit OP5, a resistor R3a connected to the inverting input terminal of the amplifier circuit OP5 and the emitter of the transistor Q2a, and a transistor Q2a whose base and collector are grounded. It is configured.

An outline of the principle of generating a reference current with less temperature dependency for the reference current circuit 400 configured as described above will be described.
The following equation holds for the non-inverting amplifier circuit 410.

（４．１）式より、

ここで、ＶＢＧは温度Ｔおよび電源電圧Ｖｄｄに依存しない基準電圧であり、またＲ１およびＲ２は正の温度係数をもつ抵抗である。温度をＴとすると、

From equation (4.1)

Here, VBG is a reference voltage independent of the temperature T and the power supply voltage Vdd, and R1 and R2 are resistors having a positive temperature coefficient. If the temperature is T,

Ｒ１とＲ２の比は、温度が変化しても同じであるので、（４．２）式より、出力電圧Ｖｏｕｔ４は温度に依存しないことがわかる。
また、電流源回路１２０に対して次式が成り立つ。

Since the ratio of R1 and R2 is the same even when the temperature changes, it can be seen from the equation (4.2) that the output voltage Vout4 does not depend on the temperature.
Further, the following equation holds for the current source circuit 120.

（４．３）式より、

（４．４）式の両辺を温度Ｔで偏微分すると、

また、

および、Ｖｏｕｔ４＞ＶＢＥより、（４．５）式の右辺第１項は正、右辺第２項は負となり、（４．５）式右辺が０となるように各パラメータを調整することによって、温度依存性の少ない参照電流Ｉｒｅｆ４を発生させる。このようにトランジスタＱ１の温度特性は、抵抗Ｒ３の温度特性によって補償されることになる。
渡辺嘉二郎、中村哲夫 共著、「アナログＬＳＩ設計の基礎」、オーム社、２００６、ｐ１４９−ｐ１５１

From equation (4.3)

When both sides of the formula (4.4) are partially differentiated by the temperature T,

Also,

From Vout4> VBE, by adjusting each parameter so that the first term on the right side of the formula (4.5) is positive, the second term on the right side is negative, and the right side of the formula (4.5) is zero. A reference current Iref4 with little temperature dependency is generated. Thus, the temperature characteristic of the transistor Q1 is compensated by the temperature characteristic of the resistor R3.
Coauthored by Watanabe Yoshijiro and Nakamura Tetsuo, “Basics of Analog LSI Design”, Ohmsha, 2006, p149-p151

In recent years, in the field of semiconductor integrated circuits, with the miniaturization of resistance, the temperature dependence of the resistance value has become extremely small. Even if each parameter is adjusted, there is a limit to the range that can be actually adjusted. Therefore, in the conventional configuration, it is difficult to reduce the temperature dependence of the reference current.
The present invention solves the above-described conventional problems, and provides a reference current circuit that can reduce the temperature dependence of a reference current even when a resistance having a very small temperature dependence is used. Objective.

  In order to solve the above-described problem, a reference current circuit according to the present invention includes a voltage generation circuit that receives a temperature-compensated reference voltage and generates a predetermined voltage at an output point, and a resistor connected to the output point of the voltage generation circuit. And a second semiconductor element that receives a voltage equivalent to the inter-terminal voltage generated between the terminals of the first semiconductor element and causes a current corresponding to the voltage to flow. A current source circuit including a mirror, wherein the voltage generation circuit includes a third semiconductor element having a temperature characteristic equivalent to that of the first semiconductor element with respect to an inter-terminal voltage, and the predetermined voltage is set to the reference voltage. The circuit is configured to be the sum of the temperature compensated voltage component and the voltage component corresponding to the voltage across the terminals of the third semiconductor element.

  According to the above configuration, the temperature dependency of the reference current can be reduced even when a resistor having extremely small temperature dependency is used.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a configuration of a reference current circuit according to the first embodiment of the present invention.
The reference current circuit 100 includes a non-inverting amplifier circuit 110 and a current source circuit 120 to which the output of the non-inverting amplifier circuit 110 is input.

  The non-inverting amplifier circuit 110 includes an amplifier circuit OP10 having an inverting input terminal, a non-inverting input terminal, and an output terminal, a resistor R1 inserted in a wiring connecting the inverting input terminal and the ground terminal, an output terminal, and an inverting input. It comprises a resistor R2 inserted in a wiring connecting the terminals and a transistor Q3 as a temperature compensation element. A reference voltage VBG that does not depend on the temperature T and the power supply voltage Vdd, that is, temperature compensated, is input to the non-inverting input terminal of the amplifier circuit OP10.

Since the current source circuit 120 and the reference voltage circuit 500 have the same configuration as described in the related art, description thereof is omitted.
Next, for the reference current circuit 100 of the first embodiment configured as described above, an outline of the principle of generating a reference current with little temperature dependence when the temperature coefficient of resistance is approximately zero will be described.

（１．１）式より、非反転増幅回路の出力電圧Ｖｏｕｔ１は、

ここで、ＶＢＧは温度Ｔおよび電源電圧Ｖｄｄに依存しない基準電圧であり、またＲ１、Ｒ２およびＲ３は温度係数がほぼ０の抵抗である。
温度をＴとすると、 The following equation holds for the non-inverting amplifier circuit 110.

From the equation (1.1), the output voltage Vout1 of the non-inverting amplifier circuit is

Here, VBG is a reference voltage that does not depend on the temperature T and the power supply voltage Vdd, and R1, R2, and R3 are resistors having a temperature coefficient of approximately zero.
If the temperature is T,

より、（１．２）式の右辺第１項は、温度に依存しないが、ＶＢＥ３が温度特性を持つ。
また、電流源回路１２０に対して次式が成り立つ。

（１．２）式と（１．３）式より、

よって、

となる。
ＶＢＥ３とＶＢＥ１とが同じ、もしくは、ほぼ同じであるとき、（１．４）式右辺第２項は、０とみなすことができる。
すなわち、

Thus, the first term on the right side of the equation (1.2) does not depend on the temperature, but VBE3 has temperature characteristics.
Further, the following equation holds for the current source circuit 120.

From equations (1.2) and (1.3)

Therefore,

It becomes.
When VBE3 and VBE1 are the same or substantially the same, the second term on the right side of equation (1.4) can be regarded as zero.
That is,

となる。
ここで、抵抗について

と表すと、Ｒ１、Ｒ２およびＲ３は温度係数がほぼ０の抵抗であるので、

である。
（１．５）式の両辺を温度Ｔで偏微分すると、

となり、（１．６）式は、参照電流Ｉｒｅｆ１が温度Ｔに依存しないことを表している。
したがって、図１に示した構成とすることにより、参照電流Ｉｒｅｆ１の温度依存性を少なくすることができる。

It becomes.
Where about resistance

R1, R2 and R3 are resistances having a temperature coefficient of approximately 0.

It is.
When both sides of the formula (1.5) are partially differentiated by the temperature T,

Thus, the equation (1.6) represents that the reference current Iref1 does not depend on the temperature T.
Therefore, with the configuration shown in FIG. 1, the temperature dependence of the reference current Iref1 can be reduced.

As described above, the temperature characteristic of the transistor Q1 can be canceled by inserting the transistor Q3 having the same temperature characteristic as that of the transistor Q1 into the negative feedback path of the non-inverting amplifier circuit 110. That is, the temperature dependence of the reference current Iref1 can be eliminated or reduced.
Although the transistors Q1 and Q2 are used in the current source circuit 120 of the first embodiment, MOS transistors M1 and M2 may be used as in the current source circuit 121 shown in FIG. In this case, it is desirable to use a MOS transistor having a temperature characteristic equivalent to that of the MOS transistor M1 instead of the transistor Q3.

The transistor Q3 included in the non-inverting amplifier circuit 110 uses an NPN bipolar transistor, but may be a diode connection of a PNP bipolar transistor or a PN junction diode, and any element or circuit having similar temperature characteristics may be used. There is no particular limitation.
(Second Embodiment)
FIG. 2 is a diagram showing a configuration of a reference current circuit according to the second embodiment of the present invention.

The reference current circuit 200 includes a temperature compensation circuit 210, a voltage follower 220 that receives the output of the temperature compensation circuit 210, and a current source circuit 120 that receives the output of the voltage follower 220.
The temperature compensation circuit 210 includes a transistor Q4 having a reference voltage VBG input to the emitter and a collector and a base connected, and a resistor R4 connected between the collector and base of the transistor Q4 and a power supply terminal. .

The voltage follower 220 has an inverting input terminal, a non-inverting input terminal, and an output terminal. The amplifier circuit OP20 has the collector and base of the transistor Q4 connected to the non-inverting input terminal and the inverting input terminal and the output terminal connected to each other. It is composed of
Since the current source circuit 120 and the reference voltage circuit 500 have the same configuration as described in the related art, description thereof is omitted.

Next, for the reference current circuit 200 of the second embodiment configured as described above, an outline of the principle of generating a reference current with little temperature dependence when the temperature coefficient of resistance is approximately zero will be described.
The output voltage VTC of the temperature compensation circuit 210 is

であるので、ボルテージフォロア２２０の出力電圧Ｖｏｕｔ２は、

また、電流源回路１２０に対して、第１の実施形態と同様に、次式が成り立つ。

（２．２）式と（２．３）式より、

よって、

となる。
ＶＢＥ４とＶＢＥ１が同じ、もしくは、ほぼ同じであるとき、

となる。ここで、ＶＢＧは温度Ｔおよび電源電圧Ｖｄｄに依存しない基準電圧であり、またＲ３は温度係数がほぼ０の抵抗であるので、温度をＴとすると、

Therefore, the output voltage Vout2 of the voltage follower 220 is

For the current source circuit 120, the following equation holds as in the first embodiment.

From equations (2.2) and (2.3)

Therefore,

It becomes.
When VBE4 and VBE1 are the same or almost the same,

It becomes. Here, VBG is a reference voltage that does not depend on the temperature T and the power supply voltage Vdd, and R3 is a resistor having a temperature coefficient of approximately 0.

である。
また、（２．５）式の両辺を温度Ｔで偏微分すると、

It is.
Further, when both sides of the formula (2.5) are partially differentiated by the temperature T,

となり、（２．６）式は、参照電流Ｉｒｅｆ２が温度Ｔに依存しないことを表している。
したがって、図２に示した構成とすることにより、参照電流Ｉｒｅｆ２の温度依存性を少なくすることができる。

(2.6) represents that the reference current Iref2 does not depend on the temperature T.
Therefore, with the configuration shown in FIG. 2, the temperature dependence of the reference current Iref2 can be reduced.

As described above, by using the transistor Q4 having the same temperature characteristic as that of the transistor Q1 in the temperature compensation circuit 210, the temperature characteristic of the transistor Q1 can be canceled. That is, the temperature dependency of the reference current Iref2 can be eliminated or reduced.
Although the transistors Q1 and Q2 are used in the current source circuit 120 of the second embodiment, MOS transistors M1 and M2 may be used as in the current source circuit 121 shown in FIG. In this case, it is desirable to use a MOS transistor having a temperature characteristic equivalent to that of the MOS transistor M1 instead of the transistor Q4.

Although the resistor R4 is used in the temperature compensation circuit 210, a PNP bipolar transistor having a bias voltage VBIAS input to the base may be used as in the temperature compensation circuit 211 shown in FIG. As shown in FIG. 8, the temperature compensation circuit 212 may be replaced with MOS transistors M3 and M4.
(Third embodiment)
FIG. 3 is a diagram showing a configuration of a reference current circuit according to the third embodiment of the present invention.

The reference current circuit 300 receives the temperature compensation circuit 210, the inverting amplifier circuit 320 that receives the output of the temperature compensation circuit 210, the inverting amplifier circuit 330 that receives the output of the inverting amplifier circuit 320, and the output of the inverting amplifier circuit 330. Current source circuit 120.
The temperature compensation circuit 210 includes a transistor Q4 whose emitter is grounded and whose base and collector are connected, and a resistor R4 connected to the power supply terminal and the base and collector of the transistor Q4.

The inverting amplifier circuit 320 has an inverting input terminal, a non-inverting input terminal, and an output terminal, the non-inverting input terminal is connected to the ground terminal, the inverting input terminal, and the output terminal of the temperature compensation circuit 210. And a resistor R7 inserted in the wiring connecting the output terminal and the inverting input terminal.
The inverting amplifier circuit 330 has an inverting input terminal, a non-inverting input terminal, and an output terminal, and includes an amplifier circuit OP31 in which the reference voltage VBG is input to the non-inverting input terminal, an inverting input terminal, and an output terminal of the amplifier circuit OP30. The resistor R8 is inserted into the connecting wire, and the resistor R9 is inserted into the wire connecting the output terminal and the inverting input terminal.

Since the current source circuit 120 and the reference voltage circuit 500 have the same configuration as described in the related art, description thereof is omitted.
Next, for the reference current circuit 300 of the third embodiment configured as described above, an outline of the principle of generating a reference current with little temperature dependence when the temperature coefficient of resistance is approximately zero will be described.

さらに、反転増幅回路３３０の出力電圧Ｖｏｕｔ３は、

ここで、Ｒ＝Ｒ６＝Ｒ７＝Ｒ８＝Ｒ９とすると、Ｖｏｕｔ３は、

となる。
また、電流源回路１２０に対して、第１の実施形態と同様に、次式が成り立つ。 The output of the temperature compensation circuit 210 is a voltage VBE4 between the base and emitter of the transistor Q4.
Next, when the output voltage of the inverting amplifier circuit 320 is V320,

Further, the output voltage Vout3 of the inverting amplifier circuit 330 is

Here, when R = R6 = R7 = R8 = R9, Vout3 is

It becomes.
For the current source circuit 120, the following equation holds as in the first embodiment.

（３．３）式と（３．４）式より、

よって、

となる。
ＶＢＥ４とＶＢＥ１が同じ、もしくは、ほぼ同じであるとき、

となる。ここで、ＶＢＧは温度Ｔおよび電源電圧Ｖｄｄに依存しない基準電圧であり、またＲ３は温度係数がほぼ０の抵抗であるので、温度をＴとすると、

である。
また、（３．６）式の両辺を温度Ｔで偏微分すると、

となり、（３．７）式は、参照電流Ｉｒｅｆ３が温度Ｔに依存しないことを表している。
したがって、図３に示した構成とすることにより、参照電流Ｉｒｅｆ３の温度依存性を少なくすることができる。

From the equations (3.3) and (3.4),

Therefore,

It becomes.
When VBE4 and VBE1 are the same or almost the same,

It becomes. Here, VBG is a reference voltage that does not depend on the temperature T and the power supply voltage Vdd, and R3 is a resistor having a temperature coefficient of approximately 0.

It is.
In addition, when both sides of the equation (3.6) are partially differentiated by the temperature T,

Thus, the expression (3.7) indicates that the reference current Iref3 does not depend on the temperature T.
Therefore, with the configuration shown in FIG. 3, the temperature dependence of the reference current Iref3 can be reduced.

As described above, by using the transistor Q4 having the same temperature characteristic as that of the transistor Q1 in the temperature compensation circuit 210, the temperature characteristic of the transistor Q1 can be canceled. That is, the temperature dependency of the reference current Iref3 can be eliminated or reduced.
In the above description, the resistance value is R = R6 = R7 = R8 = R9, but it may be the case where R6 = R9 and R7 = R8.

In the current source circuit 120 according to the third embodiment, the transistors Q1 and Q2 are used. However, MOS transistors M1 and M2 may be used as in the current source circuit 121 shown in FIG. In this case, it is desirable to use a MOS transistor having a temperature characteristic equivalent to that of the MOS transistor M1 instead of the transistor Q4.
Although the resistor R4 is used in the temperature compensation circuit 210, a PNP bipolar transistor having a bias voltage VBIAS input to the base may be used as in the temperature compensation circuit 211 shown in FIG. As shown in FIG. 8, the temperature compensation circuit 212 may be replaced with MOS transistors M3 and M4.

Further, a resistor may be connected between the non-inverting input terminal of the inverting amplifier circuit 320 and the ground terminal.
As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to the said embodiment. The inverting amplifier circuit 110 in the first embodiment, the temperature compensation circuit 210 and the voltage follower 220 in the second embodiment, and the temperature compensation circuit 210 and the inverting amplifier circuits 320 and 330 in the third embodiment are all output voltage Vout. Can be regarded as a voltage generation circuit satisfying the relational expression of “Vout = α × VBG + VBE”. As long as the voltage generation circuit satisfies such a relational expression, the same effect as in the above embodiment can be obtained regardless of the circuit configuration. Α is an arbitrary coefficient having extremely small temperature dependence, and VBE is a voltage between terminals of a semiconductor element having a temperature characteristic equivalent to that of the semiconductor element included in the current source circuit 120. Here, the semiconductor element means a diode-connected bipolar transistor, a PN junction diode, or a diode-connected MOS transistor. In addition, the voltage between terminals means, for example, in the case of a bipolar transistor, a voltage between base emitters (which can be said to be a collector-emitter voltage because it is diode-connected).

  The reference current circuit of the present invention is useful for a semiconductor integrated circuit or the like incorporating an analog circuit.

The figure which shows the structure of the reference current circuit concerning the 1st Embodiment of this invention. The figure which shows the structure of the reference current circuit concerning the 2nd Embodiment of this invention. The figure which shows the structure of the reference current circuit concerning the 3rd Embodiment of this invention. The figure which shows the structure of the conventional reference current circuit Diagram showing the configuration of the reference voltage circuit The figure which shows the structure of the modification of the current source circuit of 1st, 2nd or 3rd embodiment. The figure which shows the structure of the modification of the temperature compensation circuit of 2nd or 3rd Embodiment. The figure which shows the structure of the modification using the MOS transistor of the temperature compensation circuit of 2nd or 3rd embodiment.

Explanation of symbols

100, 200, 300, 400 Reference current circuit 110 Non-inverting amplifier circuit 120 having temperature compensation element 120, 121 Current source circuit 210, 211, 212 Temperature compensation circuit 220 Voltage follower 320, 330 Inverting amplifier circuit 410 Non-inverting amplifier circuit 500 Reference voltage circuit OP5, OP10, OP20, OP30, OP31, OP40 Amplifier circuit R1, R2, R3, R4, R6, R7, R8, R9 Resistor Q1, Q2, Q3, Q4, Q5, Q1a, Q2a Bipolar transistors M1, M2 , M3, M4 MOS transistor Vdd Power supply voltage Vss Ground VBG Reference voltage circuit output voltage VBE, VBE1, VBE3, VBE4 Transistor base-emitter voltage VT MOS transistor gate-source voltage VBIAS Bias voltage Vo Output voltage of the output voltage Vout4 non-inverting amplifier circuit of the output voltage Vout3 inverting amplifier circuit in the output voltage Vout2 voltage follower of the non-inverting amplifier circuit having a t1 temperature compensation element Iref1, Iref2, Iref3, Iref4 reference current

Claims (16)

A voltage generating circuit for receiving a temperature compensated reference voltage and generating a predetermined voltage at an output point;
A first semiconductor element connected to the output point of the voltage generation circuit via a resistor, and a voltage corresponding to the voltage between terminals generated between the terminals of the first semiconductor element, and receiving a current corresponding to the voltage A current source circuit including a current mirror composed of a second semiconductor element that flows;
The voltage generation circuit includes a third semiconductor element having a temperature characteristic equivalent to that of the first semiconductor element with respect to an inter-terminal voltage, and the predetermined voltage is a temperature-compensated voltage component based on the reference voltage and the first voltage 3. A reference current circuit, characterized in that the circuit is configured so as to be a sum of a voltage component corresponding to a voltage between terminals of the semiconductor element 3. The reference current circuit according to claim 1, wherein the voltage generation circuit includes a non-inverting amplifier circuit in which the third semiconductor element is inserted in a feedback path. The voltage generation circuit further includes an amplifier circuit having an inverting input terminal, a non-inverting input terminal, and an output terminal, and first and second resistors,
The reference voltage is input to the non-inverting input terminal of the amplifier circuit, the voltage of the output terminal of the amplifier circuit is output as the predetermined voltage, and the first wiring that connects the inverting input terminal of the amplifier circuit and the ground terminal The first resistor is inserted, the second resistor is inserted in a second wiring connecting the output terminal of the amplifier circuit and the inverting input terminal of the amplifier circuit, and the third semiconductor element is The reference current circuit according to claim 1, wherein the circuit is configured to be inserted into the second wiring. The reference current circuit according to claim 3, wherein each of the first and third semiconductor elements is a diode-connected bipolar transistor. The reference current circuit according to claim 3, wherein each of the first and third semiconductor elements is a PN junction diode. The reference current circuit according to claim 3, wherein each of the first and third semiconductor elements is a diode-connected MOS transistor. The voltage generation circuit further includes a voltage follower and a resistor,
The resistor is inserted in a wiring connecting a power supply terminal and an input point of the voltage follower, and the third semiconductor element is inserted in a wiring connecting the input point of the reference voltage and the input point of the voltage follower, The reference current circuit according to claim 1, wherein the reference current circuit is configured so that a voltage at an output point of the voltage follower is output as the predetermined voltage. The reference current circuit according to claim 7, wherein each of the first and third semiconductor elements is a diode-connected bipolar transistor. The reference current circuit according to claim 7, wherein each of the first and third semiconductor elements is a PN junction diode. The reference current circuit according to claim 7, wherein each of the first and third semiconductor elements is a diode-connected MOS transistor. The reference current circuit according to claim 7, wherein the resistor is a bipolar transistor having a bias voltage input to a base or a MOS transistor having a bias voltage input to a gate. The voltage generation circuit further includes first and second inverting amplifier circuits and a resistor,
The resistor and the third semiconductor element are inserted in this order in the wiring connecting the power supply terminal to the ground terminal, and the voltage at the intermediate point of the resistance and the third semiconductor element in the wiring is the first inversion amplification. Input to the circuit, the output voltage of the first inverting amplifier circuit is input to the second inverting amplifier circuit, the output voltage of the second inverting amplifier circuit is output as the predetermined voltage, and the first inversion 2. The circuit configuration according to claim 1, wherein a ground voltage is input to a non-inverting input terminal of the amplifier circuit, and the reference voltage is input to a non-inverting input terminal of the second inverting amplifier circuit. The reference current circuit described. The reference current circuit according to claim 12, wherein each of the first and third semiconductor elements is a diode-connected bipolar transistor. The reference current circuit according to claim 12, wherein each of the first and third semiconductor elements is a PN junction diode. The reference current circuit according to claim 12, wherein each of the first and third semiconductor elements is a diode-connected MOS transistor. The reference current circuit according to claim 12, wherein the resistor is a bipolar transistor having a bias voltage input to a base or a MOS transistor having a bias voltage input to a gate.

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