We have developed a SiC operational amplifier (op amp) and applied it to a pressure transmitter with high radiation resistance. The op amp was prototyped on the basis of SiC complementary MOS (CMOS) technology. Generally, in CMOS, electric charges are accumulated in the oxide film by irradiation. In op amps using CMOS, the offset voltage increases owing to the induction of defects in the semiconductor layer, which result from the accumulation of electric charges. On the other hand, SiC is a wide-bandgap semiconductor and has the characteristic that defects are less likely to be induced. The prototype SiC op amp showed radiation resistance of 2 MGy or more. We mounted this op amp on a pressure transmitter and evaluated the pressure transmitter in terms of input/output characteristics, temperature characteristics, step response, and radiation resistance. We confirmed that the measurement accuracy of the input/output characteristics and temperature characteristics was within ±0.5％. The step response was 450-455 ms. Regarding use in radiation environments, we confirmed that the transmitter can be operated at doses up to 580 kGy with a measurement error of 10％ or less. These results show that the device effectively improves the reliability of nuclear power plants.

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