Amplification device and measuring equipment

Abstract

To provide an amplification device having excellent radiation resistance, capable of reducing drift on an output value due to applying over voltage at an input voltage without requiring complicated management.SOLUTION: An amplification device includes: an amplifier circuit 10, whose differential amplification part 19 to which a pair of input signals are inputted is configured with a pair of transistors whose channels are SiC, for amplifying the difference in the voltage between the pair of input signals and output it; and a voltage control part 20 for controlling voltage at each of signal input terminals to which the pair of input signals are inputted so as to be equal to or less than the voltages of a positive power supply and a negative power supply to be supplied to the amplifier circuit 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an amplifier device and a measuring instrument for use in a radiation environment. [Background technology]

[0002] In environments exposed to radiation, such as nuclear power plants, there is a need to measure a variety of things, including temperature, water levels, and radiation. However, the semiconductor elements contained in the electronic circuits of measuring instruments deteriorate due to the ionization effect of radiation, making it difficult to use electronic circuits, especially in high-radiation environments.

[0003] One of the causes of failure of these measuring instruments due to radiation is failure of amplifier devices that contain semiconductor elements. Deterioration due to radiation in op-amps (short for operational amplifier), which are commonly used in amplifier devices, reduces output and causes the performance of the measuring instrument to deteriorate. Since op-amps amplify according to the potential difference between the input terminals using a differential amplifier circuit composed of at least two transistors, deterioration of individual transistors makes the op-amp prone to performance degradation (failure).

[0004] One effective way to ensure that electronic circuits containing semiconductor elements operate normally in a radiation environment is to change the semiconductor material of the operational amplifier from conventional Si (silicon) elements to SiC (silicon carbide) elements, which have superior radiation resistance.

[0005] The inventors have experimentally found that an operational amplifier using SiC (hereinafter also referred to as an "SiC operational amplifier") experiences drift in output value due to the effects of external noise and radiation. Patent Document 1 discloses a method for reducing drift in output value during use by irradiating a semiconductor element using SiC with radiation in advance and incorporating it into an actual device once degradation has ceased. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-043187 A Summary of the Invention [Problem to be solved by the invention]

[0007] The above-mentioned method is effective in reducing the drift of the output value of SiC op-amps, but since it uses a radiation source, it is complicated to manage and costly. Furthermore, it has been newly discovered that drift due to electrical stress must also be considered. Specifically, it has been experimentally revealed that when the input voltage to a SiC op-amp exceeds 80% of the power supply voltage Vdd or power supply voltage Vss of the SiC op-amp, positive charges are trapped in defects at the interface between the oxide film (insulating layer) and the semiconductor layer, causing the offset voltage to drift. Radiation generates electron-hole pairs at the interface, but electrons move quickly and tend to pass through the interface. On the other hand, holes move slowly and tend to remain at the interface.

[0008] Unlike conventional Si-based op-amps (hereafter referred to as "Si op-amps"), SiC op-amps have many defects at the interface. Therefore, it has been newly discovered that in order to stabilize the output of SiC op-amps, it is necessary to fully consider the drift of the output value (offset voltage) due to electrical stress, i.e., a large input voltage.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an amplifier and measuring instrument that have excellent radiation resistance and can reduce drift in output values ​​without requiring complicated management. [Means for solving the problem]

[0010] In order to solve the above problems, an amplifier device according to one embodiment of the present invention includes an amplifier circuit having a differential amplifier section to which a pair of input signals are input, the differential amplifier section being composed of a pair of transistors having SiC channels, and amplifying and outputting the voltage difference between the pair of input signals, and a voltage control section that controls the voltage of each of the signal input terminals to which the pair of input signals are input so that it is equal to or lower than the voltages of the positive and negative power supplies supplied to the amplifier circuit. A measurement device according to one aspect of the present invention includes a measurement section that outputs a signal corresponding to a measurement result for a target, and an amplifier having the above configuration that amplifies the signal output by the measurement section. Effect of the Invention

[0011] According to at least one aspect of the present invention, the amplification device and the measurement instrument have excellent radiation resistance and can reduce drift in output values ​​without requiring complicated management. Therefore, the amplification device and the measurement instrument according to one aspect of the present invention can realize accurate and stable output in a radiation environment. Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0012] [Figure 1] 1 is a diagram showing a basic configuration of an amplifier device according to an embodiment of the present invention; [Diagram 2] 1 is a graph showing an example of the amount of drift of the offset voltage after application of an overvoltage in an operational amplifier using SiC. [Diagram 3] FIG. 1 is a diagram showing an example of a circuit configuration in a case where an amplifier device is configured with an operational amplifier using SiC according to an embodiment of the present invention. [Figure 4] 1 is a diagram for explaining drift threshold values ​​with respect to input voltages for different types of operational amplifiers; [Diagram 5] 1 is a diagram showing an example of a schematic configuration of a measuring device using an amplifier device according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an example of a mode for carrying out the present invention (hereinafter referred to as an "embodiment") will be described with reference to the attached drawings. In this specification and the attached drawings, the same or similar components are given the same reference numerals, and duplicated explanations may be omitted or only differences may be described. The number of each component may be singular or plural unless otherwise specified.

[0014] [Basic configuration of the amplifier] FIG. 1 is a diagram showing a basic configuration of an amplifier according to an embodiment of the present invention. 1 includes an operational amplifier 10 and a voltage control section 20. Vin- and Vin+ are input signals to the amplifying device 1 (voltage control section 20), and Vout is an output signal from the operational amplifier 10.

[0015] The operational amplifier 10 is an example of an amplifier circuit using semiconductor elements. A positive power supply voltage Vdd and a negative power supply voltage Vss are supplied to the operational amplifier 10. The operational amplifier 10 outputs an output signal Vout in response to a differential pair of input signals.

[0016] An input signal Vin- and an input signal Vin+ are supplied to the voltage control unit 20. The voltage control unit 20 controls the voltages (negative phase "-" and positive phase "+") of the input signals to the differential amplification unit 19 of the operational amplifier 10 according to the voltages of the input signals Vin- and Vin+.

[0017] In semiconductor elements used in electronic circuits such as operational amplifiers, when the insulating layer is irradiated with radiation, electron-hole pairs are generated due to the Compton effect, and fixed charges and interface states are formed at the interface between the insulating layer and the semiconductor layer. This effect causes fluctuations in the operating threshold voltage, degrading the characteristics of the semiconductor element.

[0018] In response to this, the inventors solved the above problem by changing the material of the semiconductor element used in the operational amplifier from the conventional Si (silicon) to SiC (silicon carbide), a wideband semiconductor with excellent radiation resistance. In other words, by using SiC, the generation of interface states due to radiation exposure is suppressed, and the radiation resistance of the semiconductor element is significantly improved. Specifically, it was confirmed that while conventional Si-based operational amplifiers break down at several kGy, SiC-based operational amplifiers can operate normally in their amplification function even at radiation levels on the order of MGy.

[0019] In this way, the effects of radiation can be significantly reduced with SiC op-amps. However, SiC op-amps have the characteristic that there are more lattice defects at the interface between the semiconductor layer and the oxide layer than with conventional Si op-amps.

[0020] The inventors have demonstrated through experiments that when a strong electrical stress is applied to the input voltage of an op-amp using SiC, positive charges are trapped in lattice defects, causing the offset voltage to drift. Specifically, the drift becomes noticeable when a voltage of 90% or more of the absolute value of the power supply voltage Vdd (positive power supply) or power supply voltage Vss (negative power supply) for driving the op-amp is applied to the input terminal. In the following explanation, when we say "a certain percentage of the power supply voltage," it means the percentage of the absolute value of the power supply voltage.

[0021] [Offset voltage drift after overvoltage application] Figure 2 is a graph showing an example of the offset voltage drift amount after application of an overvoltage in an op-amp using SiC. In Figure 2, the vertical axis shows the offset voltage drift amount [mV], and the horizontal axis shows the elapsed time [h] after the overvoltage was applied.

[0022] Figure 2 shows the change in the offset voltage of an op amp after voltages of 80%, 90%, and 100% of the power supply voltage Vdd and power supply voltage Vss are applied to the negative and positive input terminals of the SiC op amp.

[0023] It can be seen that when the negative and positive phase input voltages are 80% of the power supply voltages Vdd and Vss, respectively, the amount of drift in the offset voltage is small and the drift converges within one minute. When the negative and positive input voltages exceed 80% of the power supply voltages Vdd and Vss, a drift in the offset voltage is observed.

[0024] And when the negative and positive input voltages are 90% or more of the power supply voltage Vdd and Vss, respectively, the drift amount of the offset voltage becomes significantly large. In the experiment, the drift amount becomes larger when the input voltage exceeds 3.5V (87.5%) with respect to the power supply voltage of ±4V, and becomes more noticeable when it exceeds 90%. Thus, it is observed that the drift amount gradually increases as the input voltage becomes larger than 80% of the power supply voltage.

[0025] Within one minute after application of the overvoltage, there is almost no difference in the amount of drift between 90% and 100%, but after one hour the increase in the amount of drift is smaller for the 90% case than for the 100% case. There is also a tendency for the 90% case to converge more quickly than the 100% case.

[0026] From the above results, the input voltage to the SiC operational amplifier should be equal to or lower than the power supply voltage Vdd and power supply voltage Vss, preferably 90% or lower. Strictly speaking, 87.5% or lower is preferable. More preferably, in order to operate the amplifier (measurement device) more stably, the input voltage of the SiC operational amplifier is 80% or less of the power supply voltage Vdd and the power supply voltage Vss, but the input voltage is of course equal to or greater than the operating threshold voltage of the transistors that make up the SiC operational amplifier.

[0027] In order to realize a SiC op-amp with a small drift amount of offset voltage, in the amplifying device 1 according to this embodiment, the differential amplifying section of the amplifying circuit (SiC op-amp) is configured with a pair of transistors with SiC as a channel (current path). Furthermore, the amplifying device 1 is configured to include a voltage control section that controls the voltage of each of the signal input terminals (inverting input, non-inverting input) to which a pair of input signals are input so that it is equal to or lower than the voltage of the power supply voltage Vdd and the power supply voltage Vss.

[0028] The above-mentioned configuration makes it possible to reduce the drift of the offset voltage of the SiC operational amplifier due to electrical stress without requiring the conventional complicated management. Therefore, the amplifier device 1 can achieve a stable output for a long period of time in a radiation environment.

[0029] [Circuit configuration when an amplifier is constructed using an op-amp made of SiC] FIG. 3 is a diagram showing an example of a circuit configuration in which the amplifying device 1 is configured with an operational amplifier 10 using SiC.

[0030] In the operational amplifier 10, a pair of n-type MOS field effect transistors 11 and 12, each having a channel made of SiC, constitutes a first-stage differential amplifier 19 in the differential pair circuit. Hereinafter, the field effect transistor is referred to as "FET." The gate of the n-type MOSFET 11 is connected to a signal input terminal 31 to which an input signal Vin- (inverting input) is input. The gate of the n-type MOSFET 12 is connected to a signal input terminal 32 to which an input signal Vin+ (non-inverting input) is input.

[0031] The drain of the n-type MOSFET 11 is connected to the drain of the upper-stage p-type MOSFET 13. The source of the p-type MOSFET 13 is connected to a power supply input terminal 34 to which a positive power supply voltage Vdd is supplied.

[0032] Similarly, the drain of the n-type MOSFET 12 is connected to the drain of the upper stage p-type MOSFET 14. The source of the p-type MOSFET 14 is connected to a power supply input terminal 34 to which a positive power supply voltage Vdd is supplied.

[0033] The midpoint between the drain of n-type MOSFET 11 and the drain of p-type MOSFET 13 is connected to the midpoint between the gate of p-type MOSFET 13 and the gate of p-type MOSFET 14. That is, p-type MOSFET 13 and p-type MOSFET 14 form a current mirror circuit.

[0034] The source of n-type MOSFET 11 is connected to the drain of n-type MOSFET 15, and the source of n-type MOSFET 12 is connected to the drain of n-type MOSFET 15. The source of n-type MOSFET 15 is connected to a power supply input terminal 35 to which a negative power supply voltage Vss is supplied.

[0035] The midpoint between the n-type MOSFET 12 and the p-type MOSFET 14 is connected to the gate of a p-type MOSFET 16 and one end of a capacitor C1. The source of the p-type MOSFET 16 is connected to a power supply input terminal 34, and the drain is connected to a signal output terminal 33 that outputs an output signal Vout. The other end of the capacitor C1 is also connected to the signal output terminal 33. The capacitor C1 is a phase compensation capacitor.

[0036] The anode of the Zener diode D1 is connected to the signal input terminal 31, and the cathode of the Zener diode D1 is connected to the power supply input terminal 34. In addition, the anode of the Zener diode D2 is connected to the signal input terminal 32, and the cathode of the Zener diode D2 is connected to the power supply input terminal 34.

[0037] Furthermore, the cathode of Zener diode D3 is connected to signal input terminal 31, and the anode of Zener diode D3 is connected to power supply input terminal 35. Furthermore, the cathode of Zener diode D4 is connected to signal input terminal 32, and the anode of Zener diode D4 is connected to power supply input terminal 35. Zener diodes D1 to D4 configure voltage control unit 20.

[0038] Zener diodes D1, D3 are provided as voltage protection elements between the signal input terminal 31 and the power supply input terminal 34, and between the signal input terminal 31 and the power supply input terminal 35. This makes it possible to control the voltage applied to the n-type MOSFET 11 of the operational amplifier 10 through the signal input terminal 31 and protect the operational amplifier 10.

[0039] Similarly, Zener diodes D2, D4 are provided as voltage protection elements between the signal input terminal 32 and the power supply input terminal 34, and between the signal input terminal 32 and the power supply input terminal 35. This makes it possible to control the voltage applied to the n-type MOSFET 12 of the operational amplifier 10 through the signal input terminal 32, thereby protecting the operational amplifier 10.

[0040] Furthermore, the amplifying device 1 includes a control terminal 36 for controlling the idling current Iset. The control terminal 36 is connected to the drain and gate of the n-type MOSFET 18. The source of the n-type MOSFET 18 is connected to the power supply input terminal 35. The control terminal 36 is connected to the gate of the n-type MOSFET 15 . Furthermore, the control terminal 36 is connected to the gate of the n-type MOSFET 17. The drain of the n-type MOSFET 17 is connected to the drain of the p-type MOSFET 16, and the source of the n-type MOSFET 17 is connected to the power supply input terminal 35.

[0041] The control terminal 36 for the idling current Iset is a circuit for adjusting the drive current of the operational amplifier 10, but is not essential. The current consumption of the operational amplifier 10 can be adjusted by the idling current Iset. The larger the drive current of the operational amplifier 10, the more stable the operational amplifier 10 becomes, but the current consumption increases. Therefore, the drive current is adjusted by adjusting the idling current using a resistor (not shown) connected to the control terminal 36.

[0042] In this embodiment, it is assumed that the operational amplifier 10 includes at least two transistors (differential amplifier 19) forming a differential pair, such as n-type MOSFETs 11 and 12. The differential amplifier 19 may be configured with a pair of p-type MOSFETs instead of a pair of n-type MOSFETs. In that case, the p-type and n-type of the other MOSFETs are changed as appropriate. SiC is used as the semiconductor material for the two MOSFETs that form the differential amplifier. However, MOSFETs are an example of transistors, and other field effect transistors may be used.

[0043] Furthermore, SiC may be used as the semiconductor material of the two transistors (p-type MOSFETs 13, 14) that configure the upper-stage current mirror circuit of the differential amplifier 19. Note that the function of the current mirror circuit can be substituted with a resistor, although the amplification factor will be reduced.

[0044] Of course, SiC may be used for other transistors constituting the operational amplifier 10. It is preferable to use SiC elements for the other transistors as well from the viewpoint of radiation resistance, but they may be used Si elements in an environment with a relatively low radiation dose.

[0045] The Zener diodes D1 to D4 are set so that the voltage applied to the signal input terminals 31, 32 does not exceed the range between the power supply voltage Vdd and the power supply voltage Vss. Specifically, when the power supply voltage is Vdd=4V and Vss=-4V, the Zener diodes D1 to D4 are set so that the voltage at the signal input terminals 31, 32 does not exceed 4V or fall below -4V. For example, when an input signal Vin+ of 5V is input to the amplifying device 1, the voltage at the signal input terminal 32 is clamped (limited) to 4V by the Zener diodes D2 and D4. Therefore, the non-inverting input of the operational amplifier 10 is limited to 4V, which is the same as the power supply voltage Vdd.

[0046] The amplifying device 1 according to the present embodiment described above is characterized in that a voltage protection element (voltage control unit 20) is provided at the input of the operational amplifier 10 having a SiC channel. According to this embodiment, drift of the offset voltage can be reduced even in a radiation environment with a simple configuration without the need for the conventional complicated management. Therefore, the amplifying device 1 including the operational amplifier 10 can obtain a stable output for a long period of time.

[0047] In the above configuration, the circuit elements constituting the voltage control unit 20, i.e., the voltage protection elements (for example, Zener diodes D1 to D4), may be integrated within the chip of the operational amplifier 10. With such a configuration, it is possible to reduce the drift of the offset voltage at low cost without changing the size of a conventional operational amplifier. That is, the operational amplifier 10 and the voltage control unit 20 are integrated into a single chip as a SiC-IC (Integrated Circuit). In the case of integration into a single chip, the circuit area can be reduced, which has a cost advantage.

[0048] Conversely, the voltage protection element (voltage control unit 20) may be attached externally as a peripheral circuit of the operational amplifier 10. In that case, the circuit scale of the operational amplifier 10 plus the voltage control unit 20 will be larger than that of a conventional operational amplifier, but there is an advantage that the value of the protection voltage can be flexibly changed. By providing the voltage control unit 20 as a peripheral circuit, it becomes easier to change the protection voltage (circuit constant) according to the power supply voltage for driving the operational amplifier 10.

[0049] In this embodiment, a Zener diode is used as the voltage protection element, but the voltage protection circuit (voltage control unit 20) can be configured using elements other than Zener diodes. For example, in addition to the clamp circuit using a Zener diode (FIG. 3), other possible voltage protection circuits include a clamp circuit using a diode, a clamp circuit using a varistor, and a protection circuit using a protection capacitor. When a protection capacitor is used as the voltage protection element, a capacitor is connected between the signal input terminal 31 and the ground, and between the signal input terminal 32 and the ground.

[0050] In the above configuration, it is preferable to configure the voltage protection element using a SiC element from the viewpoint of radiation resistance, however, in an environment with a relatively low radiation dose, the voltage protection element may be configured using a Si element.

[0051] In the above description, the set value (set voltage) of the voltage at which the voltage protection element (voltage control unit 20) performs protection is within the range between the positive power supply voltage Vdd and the negative power supply voltage Vss, but this is not limited to the example. As described above, in order to further reduce the drift of the offset voltage, it is desirable to set the set value of the voltage protection element to 90% or less (e.g., 87.5%) of the power supply voltage Vdd and the power supply voltage Vss. More desirably, it is 80% or less.

[0052] [Drift threshold for op-amp type and input voltage] Fig. 4 is a diagram for explaining the drift occurrence threshold with respect to the input voltage for each type of operational amplifier. In Fig. 4, the vertical axis indicates the voltage [V] of the input signal, and the horizontal axis indicates time [h].

[0053] Conventional Si op-amps have a high input signal voltage value (hereinafter referred to as the "drift threshold value") at which offset voltage drift occurs with respect to the power supply voltage Vdd and power supply voltage Vss. The drift threshold value is the input voltage value at which an unacceptable or preset drift amount occurs in the offset voltage of the op-amp. For example, when the power supply voltage is 4V, the drift threshold value Th si is a value that far exceeds 4V. Therefore, in normal applications, drift caused by input voltage is rarely a problem for Si op-amps. Si indicates the allowable input range of a Si op-amp.

[0054] On the other hand, experimental results have revealed that SiC op-amps experience drift when the input signal exceeds the power supply voltage. This is thought to be caused by positive charge trapping at the interface of the semiconductor layer of the MOSFET that makes up the SiC op-amp. Compared to Si, SiC has more defects at the interface of the semiconductor layer near the oxide film, which increases the trapping of positive charge to the defects.

[0055] Therefore, in SiC op-amps, the drift threshold Th siC is set to a value lower than the power supply voltage (e.g., 4V) and the input voltage is controlled to be lower than the power supply voltage. This reduces the trapping of positive charges at interface defects in the SiC op-amp, and achieves stable output with little offset voltage drift over a long period of time even in a radiation environment. The setting value of the voltage protection element is the drift occurrence threshold Th siC In FIG. 4, AR SiC indicates the allowable input range of the SiC op-amp. Allowable input range AR SiC is the allowable input range AR of the Si op amp. Si and its upper limit is smaller than the power supply voltage.

[0056] Although SiC is used as a semiconductor having a larger band gap than Si for semiconductor elements such as the operational amplifier 10, gallium nitride (GaN) or diamond semiconductors may also be used.

[0057] [Measuring equipment using the amplifier of the present invention] Next, a measuring instrument using an amplifier according to one embodiment of the present invention will be described with reference to FIG.

[0058] FIG. 5 is a diagram showing an example of a schematic configuration of a measuring device 40 using the amplifier device 1 according to an embodiment of the present invention. The measuring device 40 shown in the figure includes a measuring section 41 and an amplifier device 1 .

[0059] The measurement unit 41 is a circuit that outputs a signal according to the measurement result of the physical quantity, characteristics, etc. of the target. The amplifier 1 receives a pair of input signals Vin-, Vin+ output by the measurement unit 41. Then, the amplifier 1 amplifies the voltage difference between the input signals Vin-, Vin+ and outputs an output signal Vout. As shown in FIGS. 1 and 3, a positive power supply voltage Vdd and a negative power supply voltage Vss are supplied to the amplifier 1. When the voltage of the pair of input signals exceeds the power supply voltage Vdd or the power supply voltage Vss, the voltage control unit 20 (FIG. 3) controls the input voltage to a set voltage that is equal to or lower than the power supply voltage. The operational amplifier 10 performs an amplification operation based on the pair of input signals whose voltage values ​​have been adjusted by the voltage control unit 20.

[0060] Here, we will use a pressure transmitter as an example of a measuring device. Pressure transmitters that operate in high radiation environments are required to reduce initial drift. Specifically, the time it takes for the output of a SiC op-amp to stabilize after it is turned on can be as long as 60 to 200 minutes for a SiC op-amp, compared to about 10 minutes for a conventional Si op-amp. The drift amount of the offset voltage is about 1 mV to several mV, so it is small enough that it is not noticeable depending on the application. However, for example, in a pressure transmitter that measures minute differential pressure, this can lead to a measurement error of about 0.1 to 0.3%.

[0061] Experiments conducted by the present inventors have revealed that the rise characteristics of the power supply voltage and input voltage of the op-amp when the power is turned on affect the offset voltage drift. Specifically, it has been experimentally found that drift occurs when the power supply voltage or input voltage deviates from the allowable input range of the SiC op-amp during the period of several μs to several ms until the power supply voltage or input voltage stabilizes. Possible examples of input voltage deviating from the allowable input range include chattering (waveform fluctuations) and noise.

[0062] In contrast, the amplifier 1 having the above-mentioned configuration can reduce the drift of the offset voltage of the SiC operational amplifier and achieve both high radiation resistance and operational stability without the need for the conventional complicated management. Therefore, an accurate and stable output can be realized in a radiation environment. Furthermore, applying the amplifier 1 according to this embodiment to the measuring instrument 40 contributes to improving the reliability of plant operation.

[0063] The amplification device according to this embodiment can be applied to a measuring instrument that measures the state (physical quantity or characteristic) of an object, assuming use in a radiation environment. The measuring unit 41 may be any sensor that uses a sensing method to measure pressure, temperature, flow rate, water level, radiation, ultrasonic waves, etc. The measuring unit 41 may also be an image sensor. Furthermore, the measuring instrument according to this embodiment can be applied to systems and fields such as radiation utilization facilities in nuclear power plants, medical care, and space measurement.

[0064] It is preferable that the measuring unit 41 does not include electronic circuits, is an analog circuit that is relatively more resistant to radiation than a digital circuit, or is made of a wide band gap semiconductor such as SiC that has excellent radiation resistance.

[0065] The present invention is not limited to the above-described embodiment, and various other applications and modifications are possible without departing from the gist of the present invention described in the claims. For example, the above-described embodiment is a detailed and specific description of the configuration in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to a configuration having all of the components described. In addition, it is also possible to add, replace, or delete other components to a part of the configuration of the embodiment. [Explanation of symbols]

[0066] 1... Amplification device, 10... Operational amplifier, 11, 12... n-type MOS field effect transistor (n-type MOSFET), 13, 14... p-type MOSFET, 15... n-type MOSFET, 16... p-type MOSFET, 17... n-type MOSFET, 18... n-type MOSFET, 19... Differential amplifier section, 20... Voltage control section, 31... Signal input terminal (reverse phase), 32... Signal input terminal (positive phase), 33... Signal output terminal, 34... Power supply input terminal (positive power supply), 35... Power supply input terminal (negative power supply), 40... Measuring instrument, 41... Measurement section, D1 to D4... Zener diodes (voltage protection elements)

Claims

1. an amplifier circuit including a differential amplifier unit configured with a pair of transistors having SiC channels to which a pair of input signals are input, and which amplifies and outputs a voltage difference between the pair of input signals; a voltage control unit that controls the voltage of each of the signal input terminals to which the pair of input signals are input so that the voltage is equal to or lower than the voltage of a positive power supply and a negative power supply supplied to the amplifier circuit. Amplification device.

2. The voltage control unit limits each of the pair of input signals input to the differential amplifier unit of the amplifier circuit to 90% or less of the absolute value of each voltage of the positive power supply and the negative power supply.

2. The amplifier device according to claim 1.

3. The voltage control unit limits each of the pair of input signals input to the differential amplifier unit of the amplifier circuit to 80% or less of the absolute value of each voltage of the positive power supply and the negative power supply.

3. An amplifier device according to claim 2.

4. The voltage control unit is voltage protection elements provided between a signal input terminal to which one of the pair of input signals is input, and a power supply input terminal to which the positive power supply voltage is supplied and a power supply input terminal to which the negative power supply voltage is supplied; a signal input terminal to which the other of the pair of input signals is input, and a voltage protection element provided between a power supply input terminal to which the positive power supply voltage is supplied and a power supply input terminal to which the negative power supply voltage is supplied, When an input signal having a voltage exceeding a set voltage is input to each signal input terminal, each voltage protection element limits the voltage of each signal input terminal to a voltage equal to or lower than the voltage of the positive power supply and the negative power supply supplied to the amplifier circuit.

2. The amplifier device according to claim 1.

5. When an input signal having a voltage exceeding a set voltage is input to each signal input terminal, the voltage control unit limits the voltage of each signal input terminal to 90% or less of the absolute value of each voltage of the positive power supply and the negative power supply by each voltage protection element.

5. An amplifier device according to claim 4.

6. When an input signal having a voltage exceeding a set voltage is input to each signal input terminal, the voltage control unit limits the voltage of each signal input terminal to 80% or less of the absolute value of each voltage of the positive power supply and the negative power supply by each voltage protection element.

5. An amplifier device according to claim 4.

7. The voltage control unit is a capacitor provided between a signal input terminal to which one of the pair of input signals is input and ground; a capacitor provided between a signal input terminal to which the other of the pair of input signals is input and ground, When an input signal having a voltage exceeding a set voltage is input to each signal input terminal, the voltage of each signal input terminal is limited by each capacitor to be equal to or lower than the voltage of the positive power supply and the negative power supply supplied to the amplifier circuit.

2. The amplifier device according to claim 1.

8. The amplifier circuit is an operational amplifier.

2. The amplifier device according to claim 1.

9. The circuit elements constituting the voltage control section are integrated on the same chip as the amplifier circuit.

2. The amplifier device according to claim 1.

10. A measuring device including a measuring unit that outputs a signal corresponding to a measurement result of an object, and an amplifier that amplifies the signal output by the measuring unit, The amplifier device comprises: an amplifier circuit including a differential amplifier unit configured with a pair of transistors having SiC channels to which a pair of input signals are input, and which amplifies and outputs a voltage difference between the pair of input signals; a voltage control unit that controls the voltage of each of the signal input terminals to which the pair of input signals are input to be equal to or lower than the voltage of a positive power supply and a negative power supply supplied to the amplifier circuit. Measuring equipment.

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