JPS62262513A - Voltage comparison circuit - Google Patents

Abstract

PURPOSE:To improve the input/output transmission characteristic and the temperature characteristic by using a collector load of an input NPN transistor (TR) as a constant current circuit so as to activate critically a PNP TR of the next stage. CONSTITUTION:When an input of a built-in voltage VBE or over is impressed between the base and emitter of the NPN TR 1, a collector current starts flowing (point a). When the current moves on a characteristic curve L5 of the constant current circuit 5 and reaches an output current (d) of the constant current circuit 5, the current moves momentarily to a point (b) at that point of time and the base current of the PNP TR 2 flows. In this case, the collector voltage of the NPN TR 1 is lowered from the power supply Vcc by the base- emitter voltage VBE of the PNP TR 2. Then the increment becomes the base current of the PNP TR 2 and the current moves on a characteristic curve L3. Thus, the response sensitivity is improved more than that using a resistor for the collector load. In using a resistor 6 having a positive temperature characteristic, the temperature compensation is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to electronic circuits, and particularly to a voltage comparison circuit suitable for improving input/output transfer characteristics and improving discrimination performance with a simple circuit.

[Conventional technology]

〢 Conventionally, as a circuit that suppresses voltage comparison with a simple circuit configuration, for example, No. 42 of Practical Electronic Circuit Handbook 1 published by CQ Publishing Co., Ltd.
A configuration as shown in Section 6 Figure 7-53 is used. The principle diagram is shown in Fig. 2.

In FIG. 2, when the base potential Va of the NPN transistor 1 becomes higher than the built-in voltage (hereinafter referred to as vBE) between the base and emitter with respect to the emitter potential Va, the NPN transistor 1 becomes ONL, and the resistor 4 is connected to the ffl source Vcc. Current begins to flow through its collector. Then, when the voltage across the resistor 4 becomes equal to or higher than the VBE of the PNP transistor 2, the PNP transistor 2 turns on and supplies its collector current to the output circuit 3, and the output circuit receives this and the input comparison voltage reaches the specified voltage. Outputs a signal to the outside that it has been reached.

For voltage comparison, for example, the base V of NPN transistor 1
Connect either n or emitter VE to the reference voltage source, connect the voltage source to be measured to the other, and then set the base! ! ! Compare the magnitude with the voltage. Now, if the reference voltage is Vs, when the reference voltage is connected to the emitter side, the base input voltage Va is VBF! When the voltage exceeds +Vs, the base S
When the voltage is connected, the Nimitsuta input voltage VE is Vs −
When the voltage drops below VBE, the output circuit will issue a signal.

[Problem that the invention seeks to solve]

In a voltage comparator circuit, in response to changes in the input comparison voltage,
Input/output problems where the output signal is critically inverted; It is desirable to have a consistent characteristic, and it is also desirable to be able to always obtain output operation with a constant input comparison voltage even with temperature changes, etc. However, in the conventional circuit described above, There is a problem with this point, which will be explained below. In the above conventional circuit, PNP
The base-emitter of transistor 2 and resistor 4 are connected in parallel, and the collector power supply of transistor 1 is PNP.The emitter-base current of transistor 2 is I2.
and the current flow through resistor 4. Now, the potential difference between base VB and emitter VE of NPN transistor 1 gradually increases, NPN transistor 1 turns on, and resistor 4
The current flowing through the transistor 1 increases and the voltage across it becomes VB11 of the PNP transistor 2! When the base current 2 of the PNP transistor 2 reaches 2, the base current 2 of the PNP transistor 2 begins to be determined, but in order to secure a sufficient output current and operate the output circuit reliably, it is necessary to further increase the base current XZ. PNP) - Since the base current 12 of the transistor 2 is brought about by the voltage across the resistor 4, in order to increase the pace current 2, the current 1 flowing through the resistor 4 must also be increased. does not directly contribute to the output current of the PNP transistor 2, and is, so to speak, an ineffective component. For the NPN transistor 1, since it also absorbs the above-mentioned reactive component, an extra base current is required, which reduces the response sensitivity of the PNP transistor 2 to changes in the base current of the NPN transistor 1, that is, changes in the input comparison voltage. It turns out.

FIG. 3 shows the operation status of the conventional circuit shown in FIG. 2 above.

FIG. 3 is a diagram showing the load characteristics of the NPN transistor 1, with the vertical and horizontal axes representing the collector current and collector voltage of the NPN transistor 1, respectively. PNP on L
The voltage-current characteristic between the emitter and base of transistor 2, L2 is the voltage-current characteristic of resistor 4, and L4 is N P
The collector current-collector voltage characteristics of N transistor 1 are shown, and the operating point of PNP transistor 1 is Ls.
stays above. This will be explained below.

The collector current of the NPN transistor 1 begins to flow from the point at which the base-emitter potential difference, that is, the input comparison voltage, of the INPN transistor 1 reaches its built-in voltage Vna, and this point is point a in FIG. 3. When the comparison input voltage further increases and the base current of the NPN transistor 1 increases, the operating point of the NPN transistor 1 changes on the characteristic Ls of the resistor 4. Eventually, when the voltage across resistor 4 reaches VBH of PNP transistor 2, the base current of PNP transistor 2 begins to flow, and the current flowing through resistor 4 and the base current of PNP transistor 2 flow to the collector of NPN transistor 1. . Point b in FIG. 3 indicates the point at which the base current of the PNP transistor 2 begins to flow.

In addition, L3 has a characteristic that Ls and L2 are vertical, and P
One NPN transistor production point changes on this L3.

The base current of PNP transistor 2 is represented by the difference between L2 and L8 in FIG. It can be seen that compared to the characteristic Li only between the base and emitter, a larger change in the collector current of the N P N transistor 1, that is, a change in the comparison input voltage, is required to ensure the same base current. This is because the increased current of resistor 4 is effective. As described above, since the change in the base current of PNP transistor 2 in response to a change in comparison input voltage is slowed down, the response Ir of PNP transistor 2 in response to a change in input comparison voltage is
3 degrees decreases, leading to deterioration of input/output transfer characteristics.

In addition, in this conventional circuit example, when the junction temperature of the PNP transistor 2 changes, a built-in voltage V between the base and emitter
Since BE has a temperature coefficient of approximately -2mV/''C, P
The operation starting point of the NP transistor 2 changes depending on the temperature. In Fig. 3, point b is the starting point of the PNP transistor 2, but when the temperature is high, this point b moves to the point a side, and when the temperature is low, it moves to the point C side on Lz, so the output circuit 3 changes depending on the temperature. The input comparison voltage at which the two devices operate will be different. Furthermore, if the circuit shown in FIG. 2 is formed on a semiconductor substrate and made into a monolithic IC, since the resistor 4 has a positive temperature coefficient, it tends to promote fluctuations in the starting point of one PNPN transistor. Furthermore, NPN
Since the variation in vaE due to the temperature change of the transistor 1 causes a variation in the base current with respect to the input comparison voltage, this also causes the input comparison voltage at which the output circuit 3 starts operating to vary.

SUMMARY OF THE INVENTION An object of the present invention is to provide a voltage comparison circuit that improves input/output transfer characteristics with a simple circuit configuration and can stably perform voltage comparisons even with temperature changes.

[Means for solving problems]

For the above purpose, a constant current circuit is provided between the collector of the NPN transistor 1 and the power supply 700 in FIG.

By connecting the base of PNP transistor 2 between this constant current circuit and the collector of NPN transistor 1,
Input/output transfer characteristics can be improved, and temperature compensation for the PNP transistor 2 can also be achieved.

Furthermore, temperature compensation for the NPN transistor 1 can be achieved by providing a series resistor at the emitter of the NPN transistor 1. Furthermore, by biasing the emitter of the PNP transistor 2 to a voltage lower than the voltage WXvcc, the voltage comparison circuit can be operated in the stable operation region of the constant current circuit, and a more practical circuit can be obtained. .

[Effect]

When the collector current of NPN transistor 1 exceeds the output current of the constant current circuit, the base current of PNP transistor 2 begins to flow. After that, even if the collector current of NPN transistor 1 increases due to a change in the input comparison voltage, the output current of the constant current circuit remains constant, so any change in the collector current becomes a change in the base current of PNP transistor 2, and P Critical operation of the N P transistor 2 can be expected. Also PNP transistor 2-(7)
Even if V Be changes with temperature, the base current of PNP transistor 2 will not flow unless the collector current of NPN transistor 1 exceeds the constant current value. Therefore, PNP transistor 2 always operates under the same conditions. As a result, a stable voltage comparison operation can be performed against changes in the temperature of the PNP transistor 2.

When a circuit is formed on a semiconductor substrate, a resistor has a positive temperature coefficient, so if it is connected in series with the emitter of NPN transistor 1, the vB of NPN transistor 1 will be reduced.
8. Can compensate for temperature changes. This compensation operation is NP
When the collector current of N transistor 1 reaches a constant current value, the change in voltage across the resistor due to temperature change in resistance value and N
VFI of PN transistor 1! ! It seems that the temperature change is about the same.

This can be achieved by selecting the constant current value and resistance value.

Also, the emitter of PNP transistor 2 is connected to the power supply Vcc.
If the voltage is biased to a lower voltage, a large shared voltage of the constant current circuit can be secured, which is effective in stabilizing the operation of the constant current circuit. Also, the VRE of PNP transistor 2
Since a sufficient voltage shared by the constant current circuit can always be ensured even with temperature changes, sufficient temperature compensation can be made for the operation of the PNP transistor 2, making it possible to obtain a more practical circuit.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 shows a first embodiment of the present invention.

In FIG. 1, a constant current circuit 5 is connected between the collector of an NPN transistor 1 whose base and emitter are input terminals for voltage comparison and a power supply Vcc, and the base of a PNP transistor 2 is an NPN transistor 1. Noko,
The collector is connected to the power supply Vcc, and the collector is connected to the output circuit 3.

The operation of this embodiment will be explained using FIG. 4.

Figure 4 shows the load characteristics of the NPN transistor 1 in Figure 1, with the vertical and horizontal axes representing each NPN transistor.
l~ indicates the collector current and collector voltage of transistor 1. Also, LX in the figure represents the emitter-base voltage-current characteristic of PNP transistor 2.

La indicates the collector voltage-collector current characteristic of the NPN transistor 1, and Ls indicates the voltage-current characteristic of the constant current circuit 5, respectively.

Now, when an input comparison voltage higher than the built-in voltage Vaε is applied between the base and emitter of the NPN transistor 1, the NPN transistor 1 turns ON and a collector current starts to flow. This point is point 8 in FIG. 4, and from then on, as the input comparison voltage increases, the operating point of the NPN)- transistor 1 changes on the characteristic Ls of the constant current circuit 5, but N
When the collector current of the PN transistor 1 reaches the output current value d of the constant current circuit 5 shown at point b', the operating point instantaneously moves to point b. Here, point b indicates the point at which the base current of PNP transistor 2 begins to flow, and at this time, the collector voltage of NPN)-transistor 1 is
It is at a point lower than c by the built-in voltage VnE between the base and emitter of the PNP transistor 2. After that, the output current of the constant current circuit 5 is kept at a constant value d, so the NPN
All increases in collector current of transistor 1 are PNP
) - the base current of the transistor 2, and the operating point is as L3<base-emitter of the PNP transistor 2 [1 voltage -
As a result, the response sensitivity of the PNP transistor 2 to changes in the collector current of the NPNh transistor 1, that is, changes in the input comparison voltage, is compared to the conventional one. , and the input/output transfer characteristics are improved.

In addition, in this embodiment, even if the VBE of the PNP transistor 2 varies depending on the temperature, the PNP ()-
The starting point of operation of transistor 2 is the characteristic LI of constant current circuit 5.
Since it moves on I, as long as point b is on the left side of point b', that is, within the constant current operation area of constant current circuit 5, N
When viewed from the collector current or base current of the P N transistor 1, the PNP transistor 2 always starts operating at the same current value, so that the input comparison voltage value at which the output circuit operates can be kept constant.

FIG. 5 shows a second embodiment of the invention.

In FIG. 5, N in the first embodiment of the present invention is shown.
A resistor 6 is connected between the emitter of the PN transistor 1 and the comparison voltage input terminal VE on the emitter side. When the circuit of this embodiment is formed on a semiconductor substrate, the resistor has a positive temperature coefficient, while the built-in voltage VBE between the base and emitter of the transistor has a negative temperature coefficient. The circuit of this embodiment utilizes this property to make it possible to compensate the temperature of the NPN transistor 1.

In FIG. 5, the output circuit 3 operates almost in NPN.
This is the point in time when the collector current of the transistor 1 reaches the constant current value of the constant current circuit 5. Therefore, let the constant current value be Ic, and N
The temperature change in VBH of PN transistor 1 is ΔVBE,
If the temperature change of the resistor 6 is ΔR8, by designing the resistance value or constant current value of the resistor 6 so that 1ΔVaal: ΔR5XIc, the input comparison voltage is always constant even with the VIII2 temperature change of the NPN transistor 1. The output circuit 3 can be operated at.

According to this embodiment, it is possible to perform temperature compensation for the entire circuit, such as when it is implemented as a monolithic IC, and to obtain a voltage comparison circuit with good input/output transfer characteristics.

FIG. 6 shows a third embodiment of the present invention.

In FIG. 6, the emitter of the PNP transistor 2 in the above embodiment is connected to the midpoint of a resistor 7 and a resistor 8 which are connected in series between the power supply Vcc and GND, and m
Pierced to a voltage VEP lower than gV CC. Further, the constant current circuit 5 in the above embodiment is shown as an example of a configuration based on a PNP transistor 12 and a resistor 9.10°11.

The operation in this embodiment will be explained below using FIG. 7.

FIG. 7 shows the load characteristics of N P N transistor 1 in FIG. 6, and the vertical and horizontal axes represent each NPN
The collector current and collector voltage of transistor 1 are shown.

Further, L3 in the figure represents the operating point locus of the NPN transistor 1, and L4 represents the collector current of the NPN transistor 1 -
L6 represents the output characteristics of the constant current circuit 5, and Ll represents the base current characteristics of the PNP transistor 2.

NPN transistor 1 is now connected between comparison input terminals VB and VE.
When an input comparison voltage higher than the built-in voltage VBE between the base and emitter of
N and collector current begins to flow.

This point is point a in FIG. 7, and from then on as the input comparison voltage increases, the operating point of the NPN transistor 1 changes on the characteristic Ls of the constant current circuit 5, but the collector current of the NPN transistor reaches point b'. When the output current of the constant current circuit 5 reaches d or more as shown by , the operating point momentarily changes to b.
transition to a point.

Here, point b indicates the point where the base current of PNP transistor 2 begins to flow, and at this time, the collector electricity of the NPN transistor voltage star is the built-in voltage between the base and emitter of PNP transistor 2, which is further than the emitter bias of PNP transistor 2 [1Vap]. VBE
The voltage will drop by that amount. From then on, since the output current of the constant current circuit 5 is kept at a constant value d, all the increase in the collector current of the NPN transistor becomes the base current of the PNP transistor 2, and the operating point is the superposition of L6 and Ll and remains above 8. do. The slope of L3 after point Lr or b depends on the resistance 7.

The effects of this embodiment will be explained below.

The ideal characteristic of the constant current circuit 5 is d in FIG.
, e, and a, and this means that a constant current output can be obtained even in a voltage region where the voltage across the constant current circuit 5 is extremely small.

However, in reality, when a constant current circuit is configured as shown in FIG. 6 of this embodiment, in order to obtain a stable constant current output, it is clear that a voltage at least higher than the voltage drop across the resistor 9 must be applied to the constant current circuit 5. must be applied. Therefore, as an example of the characteristics of an actual constant current circuit, the characteristics have a slope as shown at point a-b' in FIG.

If the potential difference between points a and b' is PNP transistor 2
If the base-emitter built-in voltage VBE is greater than the base-emitter built-in voltage VBE, when the emitter of the PNP transistor 2 is connected to the power supply Vcc, its operation starting point will be between a-57, which will impair the effects of the present invention.

According to this embodiment, the emitter level of the PNP transistor 2 can be freely set by the resistors 7 and 8, and therefore the operation starting voltage of the PNP transistor 2, that is, the 7th
Point b in the figure can be set at a voltage at which the constant current circuit 5 operates stably, that is, at a point with sufficient margin relative to point b' in FIG.

Therefore, the V[I E 'GA ratio of the PNP transistor 2 can be changed to have a margin, and the constant current circuit 5
It is possible to provide a sufficient margin for variations in characteristics, that is, variations in point b', and a practical circuit can be obtained.

FIG. 8 shows a fourth embodiment of the present invention.

In FIG. 8, a PNP transistor 2 in the above embodiment is shown.
A P-channel field effect transistor 9 is provided instead, the source is placed between the resistors 7 and 8, and the gate is an NPN transistor.
) - drain to collector of transistor 1, output circuit 3
is connected to.

In this embodiment, when the collector current of the NPN transistor 1 exceeds the output current of the constant current circuit 5.

The NPN transistor 1 shifts to the saturation region, and its collector potential, that is, the gate potential Vc of the P-channel field effect transistor 9, decreases to Vo″F VE+ Ra X I c+ Vcps. Here, V[ is the potential of the comparison input terminal VE, Re is the resistance value of the resistor 6, Ic is the output current of the constant current circuit 5, and V
CES represents the saturation voltage of NPN I-transistor 1. At this time, if the potential difference between the source and gate of the P-channel field effect transistor 9 is equal to or higher than its threshold voltage Vtb, the P-channel field effect transistor 9 is turned on and the output circuit 3 is operated. The reason why the source of the P-channel field effect transistor 9 is connected to the resistors 7 and 8 in FIG. 8 is to expand the degree of freedom in designing its threshold voltage V th . The source may be directly connected to the power supply vcc as long as it has a voltage necessary for stable operation, that is, a threshold voltage equal to or higher than the potential difference between points Qt-b' in FIG.

According to this embodiment, the same effects as those of the previous embodiment can be obtained.

FIG. 9 shows a fifth embodiment of the present invention.

In FIG. 9, an NPN transistor 1 in the above embodiment is shown.
Instead, an N-channel field effect transistor 10 is provided, and voltage comparison is performed between its gate and source. Since the threshold voltage V th of a field effect transistor generally has a negative temperature coefficient, if the resistor 6 is provided, temperature compensation of the N-channel field effect transistor 10 can be performed as in the case of the NPN transistor 1 in the above embodiment. It is possible.

According to this embodiment, the same effect as in the previous embodiment can be obtained, and especially when the output impedance of the comparison input voltage source is high, if this is connected to the gate terminal Va, the input current will flow to the gate terminal. Since no current flows, the detection accuracy of the input comparison voltage can be improved.

FIG. 10 shows an example of application of the present invention.

In FIG. 10, the voltage is determined by a resistor 10 and a resistor 11 connected in series between the power supply Vcc and the OND, a PNP transistor 12° whose base is connected to the midpoint thereof, and a resistor 9 connected between its emitter and the voltage gVcc. A current circuit 5 is constructed in which the collector of the PNP transistor 12 is connected to the collector of the voltage comparison NPN transistor 1. The base of the N P N transistor 1 is connected to the midpoint of a resistor 13 and a resistor 14 connected in series between agvcc and OND, and its emitter is connected via a resistor 6 to a comparison voltage input terminal VE. In addition, the emitter of the PNP transistor 2 is connected to the midpoint of the resistor 7 and resistor 8 which are connected in series between fM, WXV cc and OND,
The base is connected to the collector of the NPN transistor 1, and the emitter is connected to the output circuit 3. Furthermore power supply vcc
A resistor 15 is connected between VE and the comparison voltage input terminal VE.
A resistor 16 is connected between them.

1 exemption According to this application example, the resistance value detection circuit can be used in practice.

This will be explained below.

N P N The base of transistor 1 is resistor 13°14
The NPN transistor 1 is turned on, and the same operation as in the previous embodiment is performed. The potential of the comparison voltage input terminal VE becomes a divided potential of the power supply voltage Vcc depending on the resistance ratio of the resistors 15 and 16. Therefore, first find the resistance ratio between resistors 15 and 16 so that the circuit operates using a known resistance, then connect the unknown resistor to either resistor 15 or resistor 16, and connect the known resistor to the other. If we find the resistance value at which the circuit operates, we can find out the value of the unknown resistance from that resistance value and the previous resistance ratio.

In this application example, the comparison input voltage is resistor 13.14 and resistor 1
5.16, so even if the power supply Vcc fluctuates, the divided potentials are in the same phase in terms of comparison, and the influence thereof can be almost eliminated. According to this application example, a resistance value detection circuit that is resistant to power supply voltage fluctuations can be obtained.

This application example is particularly effective for systems that detect whether a specified resistance has been reached. That is, as mentioned above, the resistance ratio of the resistors 15 and 16 at which the circuit operates is determined in advance, the resistor to be detected is connected to either the resistor 15 or 16, and the resistor to be detected is connected to the specified resistance at the other resistor. The resistance value can be set based on the resistance ratio determined for the daylight at which the circuit operates when . In this case 1, due to the characteristics of the voltage comparator circuit of the present invention, slight fluctuations in the comparison input voltage,
In other words, it captures subtle fluctuations in detection resistance.

Since an output can be obtained, a resistance detection circuit with good detection accuracy can be obtained. A specific example of detecting such resistance fluctuations is temperature detection using a thermistor, etc.6
Since the resistance value of the thermistor changes depending on the temperature, temperature control etc. can be performed by detecting the change in the resistance value of the thermistor.

When using a thermistor, it is necessary to be careful about heat generation in the thermistor. This is because when self-heating occurs, the resistance value of the thermistor changes, making accurate temperature detection impossible.

When it is desired to suppress heat generation, that is, generated loss, in a resistor to be detected, not just a thermistor, in the configuration shown in FIG.
This is not preferable because current flows more than c. In order to solve this problem, in FIG.
It is sufficient to provide a switch capable of 0N-OFF control between the and OND, and control the time that the current flows through the detected resistor to suppress the average loss.
As shown in the figure.

FIG. 11 shows an example in which a thyristor 17 is used as a switch between the resistor 15 in FIG. 10 and the comparison voltage input terminal VE. This is done by drawing current.

According to FIG. 11, the thyristor 17 can be controlled ON/OFF by the control input signals of the control input terminals 19 and 20.
If a thyristor is used as a switching element as in this application example, the current flowing through the resistor to be detected, that is, the resistor 15 or 16, can be controlled by the thyristor 17. If a thyristor is used as a switching element as in this application example, the ON drive current of the thyristor can be controlled during the detection operation by the ON holding function of the thyristor. There is no need to keep flowing, and it is possible to prevent excess current from flowing into or out of the detection resistor, etc., which is effective in improving detection accuracy.

〔Effect of the invention〕

According to the present invention: 1. It is possible to obtain a critical output response to changes in comparison input voltage, improving input/output transfer characteristics,
Furthermore, a temperature-compensated voltage comparator circuit can be obtained.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a circuit diagram showing a first embodiment of the present invention, Fig. 2 is a circuit diagram showing a conventional example, Fig. 3 is a characteristic diagram showing the operation of the conventional example, and Fig. 4 is a circuit diagram showing a conventional example. The figure is a characteristic diagram showing the operation of the first embodiment of the invention, FIG. 5 is a circuit diagram showing the second embodiment of the invention, and FIG. 6 is a circuit diagram showing the third embodiment of the invention. , FIG. 7 is a characteristic diagram showing the operation of the third embodiment of the invention, FIG. 8 is a circuit diagram showing the fourth embodiment of the invention, and FIG. 9 is a characteristic diagram showing the operation of the third embodiment of the invention. FIG. 10 is a circuit diagram showing a first application example of the present invention, and FIG. 11 is a circuit diagram showing a second application example of the invention. Vcc...power supply, Va + Va...comparison voltage input terminal, 1...NPN) - transistor, 2...PNP
Transistor, 3... Output circuit, 5... Constant current circuit, 6, 7, 8° 15.16... Resistor, 9... P channel type field effect transistor, 10... N channel type electric field Effect transistor, 17...thyristor.

Claims (1)

[Claims] 1. An NPN transistor whose base and emitter are input for voltage comparison, and a PNP transistor whose base is connected to its collector and whose emitter is connected to a power supply, and between the collector of the NPN transistor and the power supply. A voltage comparison circuit characterized in that a constant current circuit is provided in the voltage comparison circuit. 2. The voltage comparison circuit according to claim 1, characterized in that a resistor is provided at the emitter of the NPN transistor. 3. A voltage comparator circuit according to claims 1 and 2, characterized in that the emitter of the PNP transistor is connected to a voltage source smaller than the power supply voltage. 4. It has an NPN transistor whose base and emitter are inputs for voltage comparison, and a P-channel field effect transistor whose collector is connected to the gate, power supply, and source.
A voltage comparison circuit characterized in that a constant current circuit is provided between a collector of a PN transistor and a power supply. 5. It has an N-channel field effect transistor whose gate and source are inputs for voltage comparison, and a P-channel field effect transistor whose drain is connected to the gate, the power supply, and the source. A voltage comparison circuit characterized in that a constant current circuit is connected between the voltage comparison circuit and the voltage comparison circuit.