MAGNETIC SUBSTANCE DETECTOR

摘要

PROBLEM TO BE SOLVED: To provide a magnetic substance detector capable of preventing a malfunction due to an external magnetic field. SOLUTION: This magnetic material detector 10 includes an amplifying transistor 12. A first resistor block 14 is connected between a base and an emitter of the amplifying transistor 12. A series circuit formed of a constant current circuit 16 and a chattering preventing resistor 18 is connected between a collector and the base of the amplifying transistor 12. The constant current circuit 16 includes a FET 20 and a second resistor block 22. The first resistor block 14 and the second resistor block 22 respectively include a semiconductor magnetic resistor element. The first resistor block 14 and the second resistor block 22 are set so that one of them reacts with a magnetic material stronger than the other and that both of them react with an external magnetic field at a similar degree.