JP2010049421A - Low-voltage operation constant voltage circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-voltage operation constant voltage circuit having an excellent temperature property, providing stable output voltage regardless of a temperature change, which is low voltage of about 0.6 V, for example. <P>SOLUTION: This low-voltage operation constant voltage circuit has, as a basic constituent element, a band gap reference voltage circuit including a resistor diode series circuit wherein a resistor and a diode-connected bipolar transistor are connected in series such that constant current flows. The low-voltage operation constant voltage circuit is provided with an output circuit connected in parallel to the resistor diode series circuit, and configured such that the same constant current as the current flowing through the resistor diode series circuit flows. The output circuit has a diode-connected MOS transistor, and is configured such that a positive temperature coefficient of the current flowing through the output circuit is counteracted by the MOS transistor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a low voltage operation constant voltage circuit, for example, operates with a power supply voltage as low as about 1 V, and is able to obtain a stable output voltage with a low voltage of about 0.6 V regardless of temperature changes. The present invention relates to a low voltage operation constant voltage circuit having excellent temperature characteristics.

  In recent years, there are many products designed to be driven at a low voltage in order to reduce the size and weight. In this type of product, a low and stable reference voltage is required to drive the circuits in the product. As a circuit to obtain a stable output voltage, a constant current source having a positive temperature coefficient has been conventionally produced, and the positive temperature coefficient of the voltage appearing in the resistance and the negative temperature coefficient of the base-emitter voltage of the diode-connected bipolar transistor There is known a bandgap reference voltage circuit configured to cancel the above.

  A typical band gap reference voltage circuit using a conventionally known bipolar transistor is shown in FIG. In this reference voltage circuit, a first transistor Q1 having a unit emitter area, the bases of which are commonly connected to each other, a second transistor Q2 having an emitter resistance R1 and an emitter area of m (m is a positive number) times, a diode A third transistor Q3 connected, a diode-connected fourth transistor Q4 for self-biasing the transistors Q1 and Q2, and a fifth transistor, and a sixth transistor having the collector of the transistor Q5 connected to the base And. The collector of the transistor Q6 drives the transistor Q3 via the resistor R2 to provide an output.

Since the base-emitter voltage V _BE3 of the third transistor Q3 has a negative temperature characteristic and the collector current I has a positive temperature characteristic, the temperature characteristic at both ends of the resistor R2 becomes positive. Therefore, by connecting the resistor R2 and the transistor Q3 in series, the positive temperature coefficient and the negative temperature coefficient are canceled out, and a stable output voltage can be obtained regardless of the temperature change.
Japanese Patent No. 2734964 Japanese Patent No. 2745610

  However, in the above-described conventional reference voltage circuit, if the reference voltage is not equal to the energy band gap voltage (about 1.2 V), the temperature coefficient cannot be made zero, so that the output voltage is only about 1.2 V. And the power supply voltage must be higher (eg 2V). Therefore, it cannot be driven with a low power supply voltage. Also, since the output voltage is high, there is a difficulty that it cannot be used as a reference voltage source for a reset circuit of a microcomputer that requires a low reference voltage of about 0.6 V, for example.

  In view of the above-described problems of the prior art, the present invention can be driven even with a power supply voltage as low as about 1 V, for example, and has a low output voltage of about 0.6 V and a stable output voltage regardless of temperature changes. An object of the present invention is to provide a low voltage operation constant voltage circuit excellent in temperature characteristics that can be obtained.

  Thus, in the low voltage operation constant voltage circuit according to the present invention, in the low voltage operation constant voltage circuit having the band gap reference voltage circuit as a basic component, the same constant current as in the band gap reference voltage circuit flows. An output circuit is provided, and a diode-connected MOS transistor is provided in the output circuit, thereby canceling the positive temperature coefficient of the current flowing therethrough.

  That is, according to the first aspect of the present invention, there is provided a bandgap reference voltage circuit including a resistor-diode series circuit configured such that a constant current flows through a resistor and a diode-connected bipolar transistor connected in series. Low voltage operation constant voltage circuit provided as a basic component, connected in parallel to the resistor / diode series circuit, and configured to output the same constant current as the current flowing through the resistor / diode series circuit A circuit is provided, and the output circuit includes a diode-connected MOS transistor, and is configured to cancel the positive temperature coefficient of the current flowing through the output circuit by the MOS transistor.

  According to a second aspect of the present invention, a first series circuit in which a MOS transistor and a diode-connected bipolar transistor are connected in series, a MOS transistor, a resistor, a diode-connected bipolar transistor, Are connected in series, the collector voltage of the bipolar transistor of the first series circuit is compared with the voltage at one end of the resistor of the second series circuit, and the first series circuit is compared. In a low voltage operation constant voltage circuit having a band gap reference voltage circuit that is controlled so that the current of the circuit and the current of the second series circuit are equal to each other, the first MOS transistor is further diode-connected. And a second MOS transistor connected in series, and the same current as the current flowing through the first series circuit and the second series circuit. An output circuit current is controlled to flow, and is characterized in that it is adapted to obtain an output voltage from a connection point between said first and second MOS transistors.

  As the diode-connected MOS transistor constituting the output circuit, a transistor having a desired temperature characteristic can be obtained by using a transistor whose width W and length L are appropriately set according to the application. Can do.

  According to the present invention, a low constant voltage (for example, about 0.6 V) excellent in temperature characteristics can be obtained easily and reliably by one MOS transistor element. In addition, since the same circuit configuration as the band gap reference constant voltage circuit is adopted as the basic configuration, variations in resistance errors and transistor ratios are cancelled, and the same accuracy can be obtained regardless of the product. Therefore, it is possible to easily and reliably obtain a low constant voltage (for example, about 0.6 V) having excellent temperature characteristics. In addition, the circuit scale can be reduced, and current consumption can be reduced.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and may be arbitrarily set within the scope of the present invention. The configuration can be changed.

FIG. 1 shows a low voltage operation constant voltage circuit according to an embodiment of the present invention. This constant voltage circuit is equipped with an operational amplifier type band gap reference voltage circuit, and is excellent in temperature characteristics that can obtain a stable output voltage regardless of temperature change with a low voltage of about 0.6 V from the output terminal _VOUT. It is a thing. In particular, this circuit is preferably used as a constant voltage power source with a minute current, for example, a reference voltage source for a reset circuit for a microcomputer. In this constant voltage circuit, the voltage is compared between the MOS transistors M11 and M26 so that the collector current I _{C (Q5)} of the transistor _Q5 is equal to the collector current I _{C (Q6) of the} transistor Q6, and the transistor M12 And M1 are provided with a differential circuit for supplying current from a current mirror circuit.

  Hereinafter, the low voltage operation constant voltage circuit according to this embodiment will be described in detail. As shown in a portion 1 surrounded by a broken line in FIG. 1, the low voltage operation constant voltage circuit includes a band gap reference voltage circuit as a basic component circuit. In the low voltage operation constant voltage circuit according to the present invention, the specific configuration of the band gap reference constant voltage circuit portion is not particularly limited. For example, the configuration using the bipolar diode shown in FIG. 3, FIG. 5 and FIG. The band gap reference constant voltage circuit of the operational amplifier type shown in FIG. 6 and various other known band gap reference constant voltage circuits can also be adopted.

  First, an improved bandgap reference constant voltage circuit using the bipolar diode shown in FIG. 3 will be described. This circuit itself has a novel configuration as a bandgap reference constant voltage circuit, and has a specific effect as described later.

  As shown in FIG. 3, in this circuit, a diode-connected transistor Q41 and a transistor Q45 are connected in series to form a first series circuit. The emitter of transistor Q41 is connected to power supply voltage Vcc, the collector is connected to the collector of transistor Q45, and the emitter of transistor Q45 is grounded.

  The transistor Q42 and the transistors Q46 to Q49 connected in parallel to each other are connected in series to form a second series circuit. The emitter of transistor Q42 is connected to power supply voltage Vcc, the collector is connected to the collectors of transistors Q46 to Q49, and the emitters of transistors Q46 to Q49 are grounded. The transistor Q41 constituting the first series circuit and the transistor Q42 constituting the second series circuit are connected at the base to constitute a current mirror circuit.

  The transistor Q43, the resistor R42, and the diode-connected transistors Q50 to Q53 are connected in series to form a third series circuit. The emitter of transistor Q43 is connected to power supply voltage Vcc, the collector is connected to the collectors of diode-connected transistors Q50 to Q53 via resistor R42, and the emitters of transistors Q50 to 53 are grounded. The base of the transistor Q43 constituting this third series circuit is connected to the collector of the transistor Q42 constituting the second series circuit. The transistors Q46 to Q49 constituting the second series circuit and the transistors Q50 to Q53 constituting the third series circuit are connected at the base to constitute a current mirror circuit.

  Furthermore, one end (the collector side connection terminal of the transistor Q43) of the resistor 42 constituting the third series circuit is connected to the base of the transistor Q45 constituting the first series circuit. The transistor Q44, the resistor R41, and the diode-connected transistor Q54 are connected in series to form a fourth series circuit. The emitter of transistor Q44 is connected to power supply voltage Vcc, the collector is connected to one end of resistor R41, and the other end of resistor R41 is connected to the collector of diode-connected transistor Q54. The emitter of the transistor Q54 is grounded. The base of the transistor Q44 is connected to the base of the transistor Q43 in the third series circuit.

In the above circuit, the collector current I _{C (Q45)} of the transistor Q45 constituting the first series circuit, the collector current I _{C (Q50)} of the transistors _{Q50 to} Q53 constituting the third series circuit, and the transistor constituting the fourth series circuit The collector current I _{C (Q54)} of _Q54 is substantially equal to each other regardless of the fluctuation of the power supply voltage Vcc,
_{IC (Q45)} = _{IC (Q50)} = _{IC (Q54)}
The above condition is established and an equilibrium state is established. Therefore, in this circuit, the output voltage V _OUT1 has a constant voltage characteristic.

In this state, as shown in FIG. 4, when an output system in which a bipolar transistor Q55, a resistor R43, and a diode-connected bipolar transistor Q56 are connected in series is added, the collector current is increased as indicated by an arrow as the current increases. The base current corresponding to 1 / hfe of the increase increases. However, in this improved circuit, since this increase amount flows through the collectors of the transistors Q46 to Q49 constituting the second series circuit, the influence on the resistor R42 constituting the third series circuit is small, and therefore the output voltage V A voltage drop of _OUT1 and _VOUT2 can be avoided. That is, as shown in FIG. 3, by separating the transistors Q46 to Q49 and Q50 to Q53 into current mirror circuits, the operation reference is handled by the transistors Q50 to Q53, the resistor R42 and the transistor Q45, and the transistors Q43, Q44 (and Q55). ) Is controlled by the transistors Q46 to Q49, thereby reducing the influence on the next stage.

  Depending on the above, in the improved new circuit shown in FIG. 3, when the collector current of the transistor Q55 connected as the output system is viewed as a constant current source, the change of the current with respect to the fluctuation of the load resistance (R43, Q56). Becomes smaller. In other words, the constant current characteristic is good.

  The band gap reference configuration circuit shown in FIG. 5 is of the operational amplifier type. This bandgap reference voltage circuit (constant voltage circuit) is composed of a left amplifier circuit and right first to fourth series circuits.

  The left part including the amplifier circuit includes bipolar transistors Q7 and Q8, MOS transistors M11, M26, M12 and M1, and a resistor R18. That is, the diode-connected bipolar transistor Q8 and the resistor 18 are connected in series, the emitter of the transistor Q8 is connected to the power supply voltage terminal Vcc, and the collector is connected to one end of the resistor R18. The other end of the resistor R18 is grounded. The bipolar transistor Q7, which is connected to the base of the bipolar transistor Q8 and forms a current mirror circuit, has an emitter connected to the power supply voltage terminal Vcc and a collector connected commonly to the sources of the MOS transistors M11 and M26. ing. The drains of the MOS transistors M11 and M26 are connected to the MOS transistor M12 and the drain of the diode-connected M1, respectively. The gates of these MOS transistors M12 and M1 are connected to form a current mirror circuit. The sources of the MOS transistors M12 and M1 are both grounded.

  In the first series circuit, a diode-connected bipolar transistor Q4 and a MOS transistor M2 are connected in series. The emitter of the diode-connected bipolar transistor Q4 is connected to the power supply voltage terminal Vcc, and the collector is MOS. Connected to the drain of the transistor M2, the source of the transistor M2 is grounded. The drain and gate of the MOS transistor M2 are connected via a resistor R0 and a capacitor C0, and the gate is connected to the drain of the MOS transistor M12 of the amplifier circuit.

  In the second series circuit, a bipolar transistor Q1 and a diode-connected bipolar transistor Q5 are connected in series. The emitter of the bipolar transistor Q1 is connected to the power supply voltage terminal Vcc, and the collector is a diode-connected bipolar. The transistor Q5 is connected to the collector. The emitter of the transistor Q5 is grounded. The collector of the bipolar transistor Q1 is connected to the gate of the MOS transistor M26 of the amplifier circuit.

  In the third series circuit, a bipolar transistor Q0, a resistor R12, and a diode-connected bipolar transistor Q6 are connected in series. The emitter of the bipolar transistor Q0 is connected to the power supply voltage terminal Vcc, and the collector is a resistor. It is connected to one end of R12. The other end of the resistor R12 is connected to the collector of a diode-connected bipolar transistor Q6, and the emitter of the transistor Q6 is grounded. The collector of the bipolar transistor Q0 is connected to the gate of the MOS transistor M11 of the amplifier circuit.

  In the fourth series circuit, a bipolar transistor Q2, a resistor R10, and a diode-connected bipolar transistor Q11 are connected in series. The emitter of the bipolar transistor Q2 is connected to the power supply voltage terminal Vcc, and the collector is a resistor. R10 is connected to one end (upper end in FIG. 6), and the other end of resistor R10 is connected to the collector of bipolar transistor Q11. The emitter of the transistor Q11 is grounded.

  The bases of the bipolar transistors Q4, Q1, Q0, and Q2 constituting the series circuits 1 to 4 are commonly connected. In the figure, m is the number of transistors connected in parallel.

  In this embodiment, the ratio of the number of transistors of the bipolar transistor Q5 constituting the second series circuit and the bipolar transistor Q6 constituting the third series circuit is set to 1: 4. However, in the present invention, the ratio of the number of these transistors is not limited to that shown in this embodiment, and can be arbitrarily set as appropriate.

The band gap reference voltage circuit 1 according to this embodiment has the same operating principle as that of a conventionally known constant current circuit. That is, the voltage at the collector terminal of the bipolar transistor Q5 in the second series circuit and the voltage at one end of the resistor R12 in the third series circuit are respectively applied to the gate of the MOS transistor M26 and the gate of the MOS transistor M11 in the amplifier circuit. By comparison, the current I _{C (Q5)} of the second series circuit and the current I _{C (Q6) of} the third series circuit are controlled to be constant currents having the same value.

Note that the ratio of the number of transistors Q5 of the second series circuit and the number of transistors Q6 of the third series circuit (shown as m in the figure) is set to 1: 4 in this embodiment. As is well known, the current I _{C (Q6)} flowing through the third series circuit is obtained by the following equation.

IC _(Q6) = (V _T ln4) / R12
Where V _T is a thermal voltage (kT / q), k is a Boltzmann constant, T is an absolute temperature, and q is an electron unit charge.

Therefore, a current having the same value as the current specified by I _{C (Q11)} = (V _T ln4) / R12 flows through the fourth series circuit.

  FIG. 6 relates to an improvement of the bandgap reference voltage circuit shown in FIG. 5, and is an improvement of PSRR (Power Supply Rejection Ratio). The differential amplifier circuit in the improved bandgap reference voltage circuit shown in FIG. 6 is also configured to include an operational amplifier. In this circuit, bipolar transistors Q7 and Q4 are used to operate even when the power supply voltage is low. The emitter of the bipolar transistor Q7 is connected to the power supply voltage terminal Vcc, and the collectors are MOS transistors M11 and M26. Commonly connected to the source. The drains of the MOS transistors M11 and M26 are connected to the MOS transistor M12 and the drain of the diode-connected M1, respectively. The gates of these MOS transistors M12 and M1 are connected to form a current mirror circuit. The sources of the MOS transistors M12 and M1 are both grounded.

  On the right side of the differential amplifier circuit, first to fourth series circuits similar to the band gap reference voltage circuit shown in FIG. 5 are provided. . In the circuit shown in FIG. 5, a bias current is generated by the power supply voltage Vcc and the resistor R18. For this reason, when the power supply voltage varies, the bias current also varies. As a result, the voltage of the source connected in common of the differential circuit of the MOS transistors M11 and M26 varies. Therefore, in-phase voltage fluctuations are applied to the gates of the MOS transistors M11 and M26, but this differential amplifying unit has a function of canceling out the in-phase signal, and the influence is reduced (below 1 kHz in the frequency characteristic diagram of FIG. 8). However, this value depends on the CMRR (Common Mode Rejection Ratio) characteristics of the operational amplifier circuit used. This is why PSRR deteriorates on the high frequency side. In contrast, the circuit shown in FIG. 6 uses its own constant current output as the bias current of the differential amplifier. Accordingly, the voltage variation of the commonly connected sources of the differential circuits of the MOS transistors M11 and M26 is reduced, and PSRR is improved even with the same amplifier configuration. As for the frequency characteristics on the high frequency side, simply adding a bypass capacitor C2 as shown in FIG. 7 improves the PSRR as shown in the frequency characteristics diagram of FIG. Therefore, it is important to improve PSRR on the low frequency side.

  The frequency characteristics of the three types of band gap reference voltage circuits described above are also shown in FIG. As is apparent from this figure, it can be seen that the circuits shown in FIGS. 6 and 7 have the most improved PSRR and good characteristics.

  Referring back to FIG. 1, the low voltage operation constant voltage circuit according to this embodiment is configured as the band gap reference voltage circuit shown in FIG. 6 for the purpose of operating with a small current so as to be a constant voltage circuit dedicated to the reset circuit. The bipolar transistors Q7, Q4, Q1, Q0 and Q2 are replaced with MOS transistors M3, M4, M5, M6 and M7. In addition, in order to reduce the current flowing through each of the transistors M3, M4, M5, M6, and M7, the ratio of the parallel connection number of the diode-connected bipolar transistors Q5 and Q6 is changed from 1: 4 to 1: 2, and the resistance The value of R12 has been changed from 8 kilohms to 300 kilohms.

  Hereinafter, the low voltage operation constant voltage circuit shown in FIG. 1 will be described in detail. As shown in FIG. 1, the constant voltage circuit includes a left amplifier circuit and first to fourth series circuits on the right side.

  The amplifier circuit includes an operational amplifier and includes MOS transistors M3, M11, M26, M12, and M1. The source of the MOS transistor M3 is connected to the power supply voltage terminal Vcc, and the drain is commonly connected to the sources of the MOS transistors M11 and M26. The drains of the MOS transistors M11 and M26 are connected to the MOS transistor M12 and the drain of the diode-connected MOS transistor M1, respectively. These MOS transistors M12 and M1 have their gates connected to form a current mirror circuit. The sources of the MOS transistors M12 and M1 are both grounded.

  On the right side of the amplifying circuit, a first series circuit in which a MOS transistor M4 and a MOS transistor M2 are connected in series, a MOS transistor M5, and a diode-connected bipolar transistor Q5 are connected in series. A third circuit in which a series circuit, a MOS transistor M6, a resistor R12, and a diode-connected bipolar transistor Q6 are connected in series, a MOS transistor M7, and a diode-connected MOS transistor M19 are connected in series. A fourth series circuit is provided. In the figure, m is the number of transistors connected in parallel.

  In this embodiment, the ratio of the number of transistors of the bipolar transistor Q5 constituting the second series circuit and the bipolar transistor Q6 constituting the third series circuit is set to 1: 2. However, in the present invention, the ratio of the number of these transistors is not limited to that shown in this embodiment, and can be arbitrarily set as appropriate.

  In the first series circuit, the MOS transistor M4 is diode-connected, the source is connected to the power supply voltage terminal Vcc, the drain is connected to the drain of the MOS transistor M2, and the source of the transistor M2 is grounded. ing. The drain and gate of the MOS transistor M2 are connected via a resistor R0 and a capacitor C0.

  The MOS transistor M3 in the amplifier circuit and the MOS transistor M4 in the first series circuit are connected to each other through gates to form a current mirror circuit. The gates of the MOS transistors M11 and M26 are respectively connected to one end of the resistor R12 constituting the third series circuit and the collector of the diode-connected bipolar transistor Q5 constituting the second series circuit. Further, the drain of the MOS transistor M12 constituting the amplifier circuit is connected to the gate of the MOS transistor M2 constituting the first series circuit.

  In the first series circuit, the MOS transistor M4 has a source connected to the power supply voltage terminal Vcc and a drain connected to the drain of the MOS transistor M2. The source of the MOS transistor M2 is grounded.

  In the second series circuit, the MOS transistor M5 has a source connected to the power supply voltage terminal Vcc and a drain connected to the collector of the bipolar transistor Q5 that is diode-connected. The emitter of the transistor Q5 is grounded.

  In the third series circuit, the MOS transistor M6 has a source connected to the power supply voltage terminal Vcc and a drain connected to one end of the resistor R12. The other end of the resistor R12 is connected to the collector of a diode-connected bipolar transistor Q6, and the emitter of the transistor Q6 is grounded.

  In the fourth series circuit, the MOS transistor M7 has a source connected to the power supply voltage terminal Vcc and a drain connected to the drain of the diode-connected MOS transistor Q19. The source of the transistor M19 is grounded.

  The first series circuit MOS transistor M4, the second series circuit MOS transistor M5, the third series circuit MOS transistor M6, and the fourth series circuit MOS transistor M7 have gates connected in common.

By the way, in the conventional bandgap reference constant voltage circuit, by using a resistor and a diode-connected bipolar transistor connected in series, the positive temperature characteristic of the voltage appearing at both ends of the resistor and the base-emitter of the transistor By offsetting the negative temperature characteristic of the voltage, a stable output voltage having a temperature coefficient of zero is obtained regardless of the temperature change. However, since the base-emitter voltage V _{BE of} the transistor is about 0.6 V, only an output voltage of about 1.2 V can be extracted.
For example, it has a difficulty that it cannot be used for a device that requires a reference voltage of about 0.6 V, such as a reference voltage source for a reset circuit of a microcomputer. Therefore, in the embodiment according to the present invention, as described above, the diode-connected MOS transistor M19 is adopted instead of the conventional resistor and diode-connected bipolar transistor connected in series. Thereby, it is possible to obtain a constant voltage output excellent in temperature characteristics while being a low voltage of about 0.6V.

Since the constant voltage circuit according to this embodiment has the same configuration as a conventionally known constant current circuit except for the fourth series circuit, the principle is also the same. That is, the voltage at the collector terminal of the bipolar transistor Q5 in the second series circuit and the voltage at one end of the resistor R12 in the third series circuit are respectively applied to the gates of the MOS transistors M26 and M11 in the amplifier circuit and the two voltages are compared. The current IC _{(Q5) of} the second series circuit and the current IC _{(Q6) of} the third series circuit are controlled so as to have a constant current of the same value.

The ratio of the number of transistors Q5 of the second series circuit and the transistor Q6 of the third series circuit is set to 1: 2 for the purpose of reducing current in this embodiment, so that it is well known. The current I _{C (Q6)} flowing through the third series circuit is obtained by the following equation.

IC _(Q6) = (V _T ln2) / R12
Where V _T is a thermal voltage (kT / q), k is a Boltzmann constant, T is an absolute temperature, and q is an electron unit charge.

Furthermore, specifically, in this embodiment, a resistor R12 having a resistance of 300K ohms is employed. Therefore, from the above formula,
IC _(Q6) = (V _T ln2) / R12
= [1.3807E-23 × 300.15 ÷ 1.6021892E-19) × 0.693147181] / R12 (27 degrees)
= (5.997307E-05 × T) ÷ R12
= 1.7928E-02 ÷ R12
≒ 0.059760589 (Micro A)
It becomes. That is, I _{C (Q6)} is about 60 nA.

  In the circuit according to the present embodiment, currents of the same value flow from the MOS transistors M3 to M7. Therefore, the entire circuit consumes 300 nA, which is five times the current value. Therefore, it can be suitably used for a reset circuit having a loose voltage rating and a severe power supply current.

A current having the same value as the current specified by I _{C (Q6)} = (V _T ln2) / R12 flows through the fourth series circuit. By the way, the temperature characteristic of the diode-connected MOS transistor M19 constituting the fourth series circuit unique to the constant voltage circuit varies depending on the ratio of the width W to the length L of the transistor. FIG. 2 shows changes in temperature characteristics when the width W and length L of the MOS transistor M19 are changed. In FIG. 2, the uppermost curve is an output temperature characteristic curve when the width W of the MOS transistor M19 is 2.5 micrometers and the length L is 70 micrometers, and the lowermost curve is the MOS transistor M19. It is an output temperature characteristic curve in case width W is 2.5 micrometers and length L is 65 micrometers. As described above, by appropriately changing the width W and the length L, a constant voltage that can be practically used in a predetermined temperature range can be taken out. Therefore, it can be understood that a low voltage constant output voltage having a desired temperature characteristic can be obtained by setting the most appropriate ratio between the width W and the length L according to the application.

1 is a low voltage operation constant voltage circuit according to an embodiment of the present invention. It is an output temperature characteristic figure of the constant voltage circuit which concerns on embodiment of this invention. It is a specific example of a band gap reference voltage circuit. It is a circuit diagram which shows the state which connected the output system to the said band gap reference voltage circuit. It is a specific example of another band gap reference voltage circuit. It is a specific example of another band gap reference voltage circuit. 8B is a circuit in which a bypass capacitor is added to the band gap reference voltage circuit shown in FIG. 8A. It is a frequency characteristic figure of each said band gap reference voltage circuit. This is a conventionally known band gap reference voltage circuit.

Explanation of symbols

1 Band gap reference voltage circuit M1-M19 MOS transistor Q5, Q6 Bipolar transistor R12 Resistance

Claims (5)

Low voltage operation constant voltage circuit comprising a bandgap reference voltage circuit including a resistor and a diode series circuit in which a resistor and a diode-connected bipolar transistor are connected in series and a constant current flows, as a basic component In
An output circuit is provided which is connected in parallel to the resistor / diode series circuit and configured to flow a constant current identical to the current flowing through the resistor / diode series circuit;
The output circuit includes a diode-connected MOS transistor, and is configured to cancel a positive temperature coefficient of a current flowing through the output circuit by the MOS transistor. A first series circuit in which a MOS transistor and a diode-connected bipolar transistor are connected in series, a MOS transistor, a resistor, and a second series circuit in which a diode-connected bipolar transistor is connected in series And comparing the collector voltage of the bipolar transistor of the first series circuit with the voltage of one end of the resistor of the second series circuit, and the current of the first series circuit and the current of the second series circuit, In a low voltage operation constant voltage circuit comprising a bandgap reference voltage circuit that is controlled to be equal to each other,
Further, the first MOS transistor and the diode-connected second MOS transistor are connected in series, and control is performed so that the same constant current as the current flowing through the first series circuit and the second series circuit flows. Output circuit,
A low voltage operation constant voltage circuit characterized in that an output voltage is obtained from a connection point of the first and second MOS transistors.   3. The low voltage according to claim 1, wherein the diode-connected MOS transistor constituting the output circuit has a desired temperature characteristic in which a ratio of a width W to a length L is appropriately set. Voltage operation constant voltage circuit.   The low-voltage operation constant voltage circuit according to claim 2, wherein the number of parallel connections of bipolar transistors constituting the first series circuit is different from the number of parallel connections of bipolar transistors constituting the second series circuit. The band gap reference voltage circuit includes a differential amplifier circuit and first to third series circuits,
The differential amplifier circuit includes a first MOS transistor, a pair of second MOS transistors, and another pair of third MOS transistors each having a gate connected to each other, the MOS transistor being diode-connected to the MOS transistor. Of MOS transistors,
The source of the first MOS transistor is connected to a power supply voltage terminal, the drain is commonly connected to the sources of the pair of second MOS transistors, and the drains of the pair of second MOS transistors are respectively connected to the other pair of second MOS transistors. The third MOS transistor is connected to the drain, and the sources of the other pair of third MOS transistors are both grounded.
In the first series circuit, a MOS transistor and a diode-connected bipolar transistor are connected in series, a source of the MOS transistor is connected to a power supply voltage terminal, and a drain is connected to a collector of the diode-connected bipolar transistor. The emitter of the connected diode-connected bipolar transistor is grounded;
In the second series circuit, a MOS transistor, a resistor, and a diode-connected bipolar transistor are connected in series, the source of the MOS transistor is connected to the power supply voltage terminal, and the drain is connected to one end of the resistor. The other end of the resistor is connected to the collector of the diode-connected bipolar transistor, and the emitter of the transistor is grounded,
In the third series circuit, a first MOS transistor and a second MOS transistor are connected in series, the source of the first MOS transistor is connected to a power supply voltage terminal, and the drain is Connected to the drain of the second MOS transistor, and the source of the second MOS transistor is grounded;
The collector of the diode-connected bipolar transistor constituting the first series circuit is connected to the gate of one MOS transistor of the pair of second MOS transistors constituting the differential amplifier circuit;
One end of the resistor constituting the second series circuit is connected to the gate of the other MOS transistor of the pair of second MOS transistors constituting the differential amplifier circuit;
The first MOS transistor constituting the third series circuit and the first MOS transistor constituting the differential amplifier circuit are connected to each other through gates,
A gate of the second MOS transistor constituting the third series circuit is connected to a drain of one MOS transistor of the other pair of third MOS transistors constituting the differential amplifier circuit;
5. The low-voltage operation constant voltage circuit according to claim 1, wherein gates of the MOS transistors constituting the first to third series circuits are connected in common.

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