JP4342352B2 - Band gap reference circuit - Google Patents

Description

  The present invention relates to a bandgap reference circuit that generates a temperature-compensated reference voltage, that is, a reference voltage that does not change even when the temperature changes.

As reported in Patent Documents 1 and 2, a bandgap reference circuit that supplies a constant reference voltage to an integrated circuit (IC) or the like with respect to a temperature change is known.
Japanese Patent Laid-Open No. 2001-154749 (see FIG. 1 of that gazette) Japanese Patent Laid-Open No. 2002-149252 (see FIG. 1 of that gazette)

FIG. 9 shows an example of a band gap reference circuit that generates the reference voltage V _BGR . The band gap reference circuit has one end connected to the operational amplifier OP21, one end connected to the output terminal OUT of the operational amplifier OP21, and the other end connected to the non-inverting terminal (+) of the operational amplifier OP21. Is connected to the output terminal OUT of the operational amplifier OP21, the other end is commonly connected to the inverting terminal (−) of the operational amplifier OP21 and one end of the third resistor R23, and a plurality of diodes (D1 to D). (N + 1)).
This diode may be a diode composed of a base and an emitter by short-circuiting the base and collector of the bipolar transistor.
Among the plurality of diodes (D1 to D (n + 1)), one diode D1 is connected to the other end of the first resistor R21. A parallel circuit including diodes (D2 to D (n + 1)) other than the diode D1 is connected to the other end of the third resistor R23.
The plurality of diodes (D1 to D (n + 1)) are all formed by the same manufacturing process, and each diode has the same structure.

The voltage (V22) between the electrodes of the diode D1 and the parallel circuit composed of the other diodes (D2 to D (n + 1)) is based on the band gap of the pn junction formed in the diode. The voltage is known to have a negative characteristic (approximately −2 mV / K) with respect to temperature rise. Further, it is a well-known fact that this band gap reference circuit satisfies the following relational expression with respect to the output voltage V _BGR .
V _BGR = V21 + (R22 / R23) · V _T · ln ((R22 / R21) · (I _S2 + I _S3 + I _S4 + ·· + I _{S (n + 1)} ) / I _S1 ))
I _S1 , I _S2 ... I _{S (n + 1)} are reverse saturation currents of the respective diodes, and V _T indicates a thermal voltage.

The area ratio of the pn junction area of the diode D1 connected to the first resistor R21, the total pn junction area of the plurality of diodes (D2 to D (n + 1)) connected to the third resistor R23, and each resistance value ( By setting R21, R22, and R23) to predetermined values, it is possible to prevent the temperature from affecting the reference voltage V _BGR . Using the above relational expression, the area ratio of the pn junction and the resistance values (R21, R22, R23) where the reference voltage V _BGR does not affect the temperature can be set, and thereby the reference voltage V which is not influenced by the temperature. _A bandgap reference circuit that outputs _BGR is obtained.

  In this type of technology, a diode formed by the same manufacturing process is used in order to set the area ratio of the pn junction of the diode to a predetermined ratio. The diodes formed by the same manufacturing process are grouped into a predetermined number of ratios to set the pn junction area ratio to a predetermined ratio. Since the diodes are formed by the same manufacturing process, the pn junction areas of the individual diodes should be equal. Therefore, the ratio of the number of diodes can be treated as it is as the ratio of the pn junction areas.

However, even if the diodes are formed by the same manufacturing process, the current manufacturing process inevitably causes variations between the diodes due to manufacturing tolerances. Therefore, even if the diodes are grouped into a predetermined number, a band gap reference circuit cannot be formed with a pn junction area ratio corresponding to the number ratio. For this reason, it has been difficult for the conventional band gap reference circuit to supply a constant output voltage by accurately compensating for the influence of temperature change.
An object of the present invention is to provide a technique for compensating for variations in the manufacturing process of a diode configured in a band gap reference circuit. As a result, an object is to realize a band gap reference circuit according to the design value.

One band gap reference circuit of the present invention includes an operational amplifier. One end is connected to the output terminal of the operational amplifier, and the other end is provided with a first resistor connected to the non-inverting terminal of the operational amplifier. Furthermore, one end is connected to the output terminal of the operational amplifier, and the other end is provided with a second resistor commonly connected to the inverting terminal of the operational amplifier and one end of the third resistor. In addition, a plurality of diodes are provided that are connected to the other end of the first resistor and the other end of the third resistor via switch means.
A switch means is prepared, and the switch means selects a plurality of diodes into two groups so as to have a predetermined division ratio, and a parallel circuit formed by one diode group is connected to the other end of the first resistor. A parallel circuit formed by the other diode group is connected to the other end of the third resistor. The switch means switches the diode group connected to the first resistor and the third resistor with time. That is, the diode group selected for the first resistor and the third resistor is changed with time.
Note that the diodes to be grouped may be grouped by one and many other relationships. In this case, one diode to be selected is connected in series with the resistor without forming a parallel circuit.
In addition, the diode here is sufficient if it has a pn junction interface in the element. For example, a diode composed of a base and an emitter by short-circuiting the base and collector of a bipolar transistor is used. May be.

Even in the case of the band gap reference circuit described above, the manufacturing process varies between the diodes. Therefore, the pn junction area formed in each diode is not constant, and the ratio of the number of transistors to be selected may not match the predetermined area ratio determined by the design value. However, in the band gap reference circuit described above, different diodes are selected over time using the switch means and connected to the respective resistors. Thus, even if the ratio of the pn junction area of the diode connected to the first resistor and the pn junction area of the diode connected to the third resistor at a certain moment deviates from the area ratio set by the design value, the switching means The ratio between the pn junction area of the diode connected to the first resistor and the pn junction area of the diode connected to the third resistor is an area set by a design value. It will match the ratio.
For example, it can be made to correspond to the area ratio set by the design value as follows. The output voltage output when the diode group connected to the first resistor and the third resistor is variously combined is measured in advance. The temperature range to be measured is set at least at its lower limit, room temperature, and upper limit in consideration of the operating environment in which this band gap reference circuit is used. As a result, the temperature characteristics of individual diodes within this temperature range or the temperature characteristics of the combination can be grasped in advance. In accordance with the grasped temperature characteristics, the combination of the diodes and the time interval for switching the switch means are adjusted. The time interval need not be a constant period.
As a result, the ratio of the pn junction area of the diode connected to the first resistor and the pn junction area of the diode connected to the third resistor can be made to coincide with a predetermined design value, and the accurately temperature compensated reference voltage can be obtained. Can be supplied. In addition, according to the present invention, even if variations in the manufacturing process of each diode occur, the variations can be compensated for, so that it can be said that it is easy to manufacture a desired band gap reference circuit with high reproducibility. It is possible to reduce defective products and is suitable for mass production.
In addition, the present invention uses a technique for compensating for the influence of variations in each diode, and not only generates a reference voltage that is maintained at a constant value with respect to a temperature change, but also, for example, a temperature change. It is also possible to supply a reference voltage that varies along a predetermined temperature coefficient.

It is preferable to further include a clock generator and a shift register circuit. Based on the pulse signal from the clock generator, the input signal to each switch provided in the switch means is switched between high and low. Each switch to which the pulse signal is supplied is switched by the shift register circuit, so that the diode connected to each resistor can be changed.
With the above configuration, the diodes to be selected can be accurately changed at a predetermined cycle. Stable operation can be realized.

It is preferable that the switching means can change the diode to be selected at a constant period. In this case, the plurality of diodes are preferably formed by the same manufacturing process. The diodes formed by the same manufacturing process vary within manufacturing tolerances. There is a variation of ± A in the pn junction area of each diode. In the present invention, this variation can be averaged as a whole to compensate for variations in individual diodes. It is not necessary to know the characteristics of individual diodes in advance, and a temperature-compensated reference voltage can be generated very easily.
The switch means can be accurately changed at a constant cycle by the clock generator and the shift register circuit. As a result, variations in the manufacturing process of each diode are averaged without deviation, so that variations in each diode are easily compensated.

In the present invention, it is possible to propose means for supplying a reference voltage with more accurate temperature compensation by taking measures against variations in the transistors forming the operational amplifier.
The operational amplifier includes a first transistor, a second transistor that forms a differential pair with the first transistor, a third transistor connected to the first transistor via a first connection point, a second transistor, and a second transistor. And a fourth transistor connected via two connection points. Further, when the potential of the inverting terminal is supplied to the gate of the first transistor, the potential of the non-inverting terminal is supplied to the gate of the second transistor, and when the potential of the inverting terminal is supplied to the gate of the second transistor, the potential is not inverted. First switch means capable of supplying the potential of the terminal to the first transistor gate is provided. Second switch means is provided that can alternately supply the potential of either the first connection point or the second connection point to the gates of the third transistor and the fourth transistor. Further, there is provided third switch means capable of alternately supplying the potential of either the first connection point or the second connection point to the output terminal. The first switch means, the second switch means, and the third switch means are switched in the same phase by the switching circuit.

In the above operational amplifier, (1) the signal from the inverting terminal is supplied to the gate of the first transistor, the potential at the first connection point is supplied to the gates of the third transistor and the fourth transistor, and the signal from the non-inverting terminal. Is supplied to the gate of the second transistor and the potential of the second connection point is supplied to the output terminal, and (2) the signal from the inverting terminal is supplied to the gate of the second transistor, and the second connection point Is supplied to the gates of the third transistor and the fourth transistor, the signal from the non-inverting terminal is supplied to the gate of the first transistor, and the potential of the first connection point is supplied to the output terminal. Can be repeated.
In order to alternately repeat the first state and the second state, the symmetry of the first transistor and the second transistor and the symmetry of the third transistor and the fourth transistor are temporally averaged and substantially compensated. .

The operational amplifier is ideally configured to have an offset voltage of 0, but in practice, it is necessary to set a predetermined offset voltage due to variations in the transistors formed in the internal circuit of the operational amplifier. There is. This is because the symmetry between the first transistor and the second transistor and the symmetry between the third transistor and the fourth transistor are not substantially realized.
In the present invention, by using the switch means, the symmetry between the first transistor and the second transistor and the symmetry between the third transistor and the fourth transistor can be substantially ensured. Therefore, it is not necessary to set the offset voltage, and the temperature-compensated reference voltage can be supplied more accurately.

Another bandgap reference circuit according to the present invention includes an operational amplifier. One end is connected to the output terminal of the operational amplifier, and the other end is provided with a first resistor connected to the non-inverting terminal of the operational amplifier. Furthermore, one end is connected to the output terminal of the operational amplifier, and the other end is provided with a second resistor commonly connected to the inverting terminal of the operational amplifier and one end of the third resistor. In addition, a plurality of diodes are provided that are connected to the other end of the first resistor and the other end of the third resistor via switch means.
A switch means is prepared, and the switch means selects a plurality of diodes into two groups so as to have a predetermined division ratio, and a parallel circuit formed by one diode group is connected to the other end of the first resistor. A parallel circuit formed by the other diode group is connected to the other end of the third resistor.
In the above band gap reference circuit, in consideration of the operating environment in which the band gap reference circuit is used, various combinations of diode groups connected to the first resistor and the third resistor within a predetermined temperature range are used. The output voltage output to is measured in advance. Thereby, the characteristic of each diode or the temperature characteristic of the combination can be grasped in advance. From the result of the grasped characteristic, the switch means is fixed to the combination that provides the optimum temperature characteristic among the combinations of the diode groups connected to the first resistor and the third resistor. Alternatively, the switch means is fixed to a combination that provides temperature characteristics that meet the actual specifications. As a result, it is possible to supply a reference voltage that is accurately temperature compensated.

  According to the band gap reference circuit of the present invention, variations in the manufacturing process between transistors can be compensated, and a constant reference voltage can be supplied with respect to temperature changes.

First, the main features of the embodiment are listed.
First Embodiment It is preferable that an LPF (Low Pass Filter) is provided on the output terminal side of the operational amplifier. The high frequency noise accompanying the switching means can be removed, and a stable reference voltage can be generated.

Embodiments will be described in detail below with reference to the drawings.
First Embodiment FIG. 1 shows an example of a band gap reference circuit according to a first embodiment.
The band gap reference circuit includes an operational amplifier OP1, a first resistor R1, a second resistor R2, a third resistor R3, a plurality of diodes (D1 to D16), and a switch means S. In this embodiment, a total of 16 diodes are used.
One end of the first resistor R1 is connected to the output terminal of the operational amplifier OP1. The other end of the first resistor R1 is connected to the non-inverting terminal (+) of the operational amplifier OP1.
One end of the second resistor R2 is connected to the output terminal of the operational amplifier OP1. The other end of the second resistor R2 is connected to the DAC, and the DAC is connected to the inverting terminal (−) of the operational amplifier OP1 and one end of the third resistor R3. An LPF (Low Pass Filter) is provided on the output terminal OUT side of the operational amplifier OP1, and cuts high frequency noise generated by switching.
As shown in FIG. 2, the DAC includes multi-stage resistors, and any one of the nodes 1 to 16 is connected to the operational amplifier OP1 based on a 4-bit signal sent from the instruction circuit D that indicates the level of the reference voltage. Input to the inverting terminal. In this circuit, the level of the reference voltage can be selected by the instruction circuit D.
The plurality of diodes (D1 to D16) are all formed by the same manufacturing method, and each diode has the same structure.

S in the figure is switch means, and FIG. 1 shows an example of a switch state at a certain moment. In the state of the switch means S, the diode D1 among the plurality of diodes is connected to the first resistor R1, and the remaining diodes constitute a parallel circuit by the switch means S and are connected to the third resistor R3. Therefore, the area ratio of the pn junction of the diode D1 connected in series with the first resistor R1 and the total pn junction area of the parallel circuit composed of the other diode groups (D2 to D16) is ideally The relationship is 1:15.
The switch means S is sorted into two groups so as to obtain a division ratio of 1:15 (in this embodiment, one diode and 15 diodes) from a plurality of diodes (D1 to D16). One selected diode is connected to the other end of the first resistor R1. A parallel circuit formed of 15 diode groups is connected to the other end of the third resistor R3.

FIG. 3 shows the state of the bandgap reference circuit after a predetermined time has elapsed. It can be seen that the switches S1 and S2 of the switch means S are switched. Thereby, the diode D2 is connected to the first resistor R1 via the switch S2, and the parallel circuit formed by the remaining diodes is connected to the third resistor R3.
Although illustration is omitted, when the next predetermined time elapses, the switch S2 and the switch S3 are switched, the diode D3 is connected to the first resistor R1, and a parallel circuit formed by other diodes is connected to the third resistor. The Thus, in this embodiment, the respective diodes are sequentially connected to the first resistor R1 with time in order from the diode D1.

This switch means S is controlled by a clock generator CL and a shift register circuit SF, and its timing chart is shown in FIG.
Sclk is a pulse signal from the clock generator CL, and S1 to S16 are input signals to the switches. Each switch is connected to the wiring connected to the first resistor R1 when the input signal is high, and is connected to the wiring connected to the third resistor R3 when the input signal is low.
The input signal to each switch is switched from low to high when the signal of the clock generator CL rises, and the state is maintained until the next rise. Then, when the signal of the next clock generator CL rises, the signal is switched from high to low. In the present embodiment, the pulse signal of the clock generator CL is sequentially input from S1 to S16 using the shift register circuit SF. Therefore, the input signal of each switch switches from low to high at the timing when the input signal to the previous switch switches from high to low, and then the timing at which the switch input signal switches from high to low. Thus, the input signal of the next switch is switched from low to high. According to this timing chart, the switch S1 is connected to the first resistor R1 in order, and when the input signal to the switch S16 is switched from high to low, the input signal to the switch S1 is switched from low to high. Accordingly, the switches S1 to S16 are repeatedly connected to the first resistor R1 at a constant cycle.

For example, when the switch S1 is connected to the first resistor R1 and the switches S2 to S16 are connected to the third resistor, the pn junction area ratio may not be 1:15. Similarly, when S2 is connected to the first resistor R1 and the switches S1 and S3 to S16 are connected to the third resistor, the pn junction area ratio may not be 1:15.
However, looking at the pn junction area of the diodes connected to the first resistor R1 and the third resistor R3 at the time interval in which all 16 switches are connected to the first resistor R1, the pn junction at each timing It can be treated as the average of the area. Each of the diodes D1 to D16 varies within the range of manufacturing tolerances, but when averaged, the variation can be treated as zero. As a result, variations in the manufacturing process of the diodes D1 to D16 are compensated. Therefore, since the band gap reference circuit can be configured with a pn junction area ratio according to a predetermined design value, a temperature-compensated reference voltage can be generated.

In place of the above-described embodiment, the generation of the temperature-compensated reference voltage can also be realized by the following method.
First, output voltages are measured in advance in 16 combinations in which each of the diodes D1 to D16 is connected to the first resistor R1. The temperature range to be measured is set in consideration of the operating environment in which the band gap reference circuit is used, and at least the lower limit (low temperature), room temperature, and upper limit (high temperature) are measured. As a result, each of the 16 temperature characteristics can be known. From this grasped temperature characteristic, for example, when only the switch S1 and the switch S2 are switched at a predetermined time interval (it is not necessary to have a constant cycle), the most temperature compensated reference voltage can be generated. If so, the switch means S is controlled using the shift register circuit SF and the clock generator CL in accordance with this setting. As a result, it is possible to generate a reference voltage that is accurately temperature compensated.
Alternatively, the switch means S may be fixed and used as long as the temperature compensation reference voltage sufficiently matching the actual specification can be generated from the grasped temperature characteristics. In this case, since the high frequency noise by the switch means S does not generate | occur | produce, it is not necessary to provide the low pass filter LPF. Configuration is simplified.
Note that a temperature sensor may be provided separately, and the switch means S may be controlled following the temperature. It is possible to use the reference voltage with more accurate temperature compensation, or to generate a desired reference voltage following the temperature change.

Even with the above measures alone, it is possible to generate a reference voltage that is sufficiently temperature compensated as compared with the prior art. However, in this embodiment, the temperature compensation is further accurately performed for the internal circuit of the operational amplifier OP1. Measures are taken to generate a reference voltage. FIG. 5 shows a specific configuration of the internal circuit of the operational amplifier OP1.
The operational amplifier OP1 includes a pMOS first transistor Tr1, a second transistor Tr2, a fifth transistor Tr5, a sixth transistor Tr6, an nMOS third transistor Tr3, a fourth transistor Tr4, and a seventh transistor Tr7. .
The first transistor Tr1 is connected to the third transistor Tr3 via the first connection point 11. The second transistor Tr2 constituting a differential pair with the first transistor Tr is connected to the fourth transistor Tr4 via the second connection point 12. The third transistor Tr3 and the fourth transistor Tr4 constitute a current mirror circuit.

First switch means Sa is provided for alternately supplying the potential of either the inverting terminal (−) or the non-inverting terminal (+) to the gates of the first transistor Tr1 and the second transistor Tr2.
Second switch means Sb for alternately supplying the potential of either the first connection point 11 or the second connection point 12 to the gates of the third transistor Tr3 and the fourth transistor Tr4 is provided.
There is provided third switch means Sc for alternately supplying the potential of either the first connection point 11 or the second connection point 12 to the gate of the seventh transistor Tr7. The capacitor C1 is a capacitor for preventing oscillation.
The fifth transistor Tr5 and the sixth transistor Tr6 are constant current generation sources, and the gate voltage Vbb is applied to both transistors.
The switch means Sa, Sb, Sc of the operational amplifier OP1 are simultaneously switched by the switching circuit SH in synchronization with the pulse signal of the clock generator CL of the switch means S shown in FIG.

Transistors are configured in a symmetrical positional relationship in the internal circuit of the operational amplifier OP1. In the above example, the first transistor Tr1 and the second transistor Tr2 are in a symmetrical positional relationship, and the third transistor Tr3 and the fourth transistor Tr4 are configured in a symmetrical positional relationship. Ideally, it is desirable that the transistors in the symmetrical positional relationship have the same structure. However, since there is actually a variation in the manufacturing process, it is necessary to apply an offset voltage to compensate for the variation. There is. Since this offset voltage affects the design value of the bandgap reference circuit, if this offset voltage is unstable, naturally it becomes difficult to compensate the temperature of the bandgap reference circuit.
In the present embodiment, the switch means Sa, Sb, Sc is used to switch over time, and realizes a state where it is not necessary to apply an offset voltage by realizing a substantial object by averaging. . Therefore, the band gap reference circuit can be configured without considering the offset voltage, and the reference voltage compensated for temperature more accurately can be supplied.

FIG. 6 shows an actual measurement value of the reference voltage generated by this embodiment, where the vertical axis represents the magnitude of the reference voltage and the horizontal axis represents time.
S1 in the figure is a reference voltage generated when the switch S1 is connected to the first resistor R1. When the switch S2 is connected to the first resistor R1 at the next timing, the magnitude of the reference voltage is S2 in the figure. Thus, looking at the reference voltage generated at the timing when each switch switches, it can be seen that the magnitude of the generated reference voltage varies greatly due to variations in each diode.
In this embodiment, since the switching of the switches is performed at an extremely short interval, the substantially generated reference voltage magnitude appears as the averaged reference voltage (broken line in the figure).
The reference voltage after passing through the LPF filter is very stable, and a temperature-compensated reference voltage can be generated.

FIG. 7 shows the magnitude of the reference voltage when the ambient temperature is changed. The result of this example is shown by a solid line. As a comparative example, the result when the switch means (S, Sa, Sb, Sc) is not provided is indicated by a broken line.
In the present embodiment shown by the solid line, substantially the same reference voltage is generated even when the ambient temperature changes. A constant reference voltage that is independent of temperature change, that is, temperature compensated, is generated. On the other hand, in the result when the switch means (S, Sa, Sb, Sc) is not provided (corresponding to the prior art), the reference voltage generated with respect to the temperature change greatly changes. Temperature compensation is not performed and a constant reference voltage cannot be generated.
As described above, when the technique of this embodiment is used, it is possible to provide a temperature-compensated reference voltage.

FIG. 8 shows a modification of the embodiment, which is an example of a band gap reference circuit that generates the reference voltage V _BGR from the power supply voltage Vcc. The power supply voltage Vcc is supplied to the anodes of the plurality of diodes (D11 to D116), and the timing at which the plurality of diodes are connected to the first resistor R11 and the third resistor R13 is switched by the switch means.
Also in this case, the temperature compensated reference voltage can be generated by the same effect as the above-described embodiment.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
Further, in this specification, the variation in the characteristics of the diode is described as the variation in the pn junction area due to manufacturing tolerances, but the cause of the variation in the characteristics of the diode is not limited to the variation in the pn junction area. This also occurs due to the impurity concentration distribution and stress distribution of the pn junction. For these causes, the temperature compensated reference voltage can be generated by using the technique of the present invention.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of purposes at the same time, and has technical utility by achieving one of the purposes.

1 shows a bandgap reference circuit of a first embodiment (1). 1 shows a DAC internal circuit of a first embodiment. 2 shows a bandgap reference circuit of the first embodiment (2). The timing chart of a clock generator and a switch means is shown. 1 shows an internal circuit of an operational amplifier according to a first embodiment. The relationship between the generated reference voltage and time is shown. Indicates the magnitude of the reference voltage under different ambient temperatures. An example of the modification of 1st Example is shown. An example of a conventional band gap reference circuit is shown.

Explanation of symbols

OP: operational amplifier SF: shift register circuit CL: clock generator R1, 2, 3: resistors S1 to S16: switches D1 to D16: diode LPF: low-pass filters Tr1, 2, 5, 6: p-type MOSFET
Tr3, 4, 7: n-type MOSFET

Claims (4)

An operational amplifier;
A first resistor having one end connected to the output terminal of the operational amplifier and the other end connected to the non-inverting terminal of the operational amplifier;
One end connected to the output terminal of the operational amplifier, the other end connected in common to the inverting terminal of the operational amplifier and one end of the third resistor;
A plurality of diodes connected to the other end of the first resistor and the other end of the third resistor via switch means;
The switch means selects a plurality of diodes into two groups so as to have a predetermined division ratio, and connects a parallel circuit formed by one diode group to the other end of the first resistor and forms the other diode group. A band gap reference circuit characterized in that a parallel circuit to be connected is connected to the other end of the third resistor and the diode group connected to the first resistor and the third resistor is switched over time. A clock generator and a shift register circuit;
Based on the pulse signal from the clock generator, the input signal to each switch provided in the switch means is switched between high and low, and each switch to which the pulse signal is supplied is switched by the shift register circuit. 2. The bandgap reference circuit according to claim 1, wherein: The operational amplifier is
A first transistor;
A second transistor constituting a differential pair with the first transistor;
A third transistor connected to the first transistor via a first connection point;
A fourth transistor connected to the second transistor via a second connection point;
When the potential of the inverting terminal is supplied to the gate of the first transistor, the potential of the non-inverting terminal is supplied to the gate of the second transistor, and when the potential of the inverting terminal is supplied to the gate of the second transistor, First switch means capable of supplying a potential to the first transistor gate;
Second switch means capable of alternately supplying the potential of either the first connection point or the second connection point to the gates of the third transistor and the fourth transistor;
Third switch means capable of alternately supplying the potential of either the first connection point or the second connection point to the output terminal;
A switching circuit for switching the first switch means, the second switch means, and the third switch means in the same phase;
The band gap reference circuit according to claim 2, further comprising: An operational amplifier;
A first resistor having one end connected to the output terminal of the operational amplifier and the other end connected to the non-inverting terminal of the operational amplifier;
One end connected to the output terminal of the operational amplifier, the other end connected in common to the inverting terminal of the operational amplifier and one end of the third resistor;
A plurality of diodes connected to the other end of the first resistor and the other end of the third resistor via switch means;
The switch means selects a plurality of diodes into two groups so as to have a predetermined division ratio, and connects a parallel circuit formed by one diode group to the other end of the first resistor and forms the other diode group. A bandgap reference circuit, wherein the parallel circuit is connected to the other end of the third resistor.

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