| 摘要 |
PROBLEM TO BE SOLVED: To attain miniaturization and low costs, and to reduce the influence of a noise as much as possible in a magnetic field sensor using a magnetic body. SOLUTION: A transmission line element 11 is inserted into the feedback circuit of a phase shift type oscillator circuit using a closed loop operating amplifier OP as an amplifier so that a magnetic field sensor can be constituted. In this magnetic field sensor, the output of the operating amplifier OP is feedbacked through the transmission line element 11 to the input of the operating amplifier OP so that the change of oscillation frequencies fc depending on the strength of an outside magnetic field Hext. can be extracted as a sensor output (OUT). Thus, the influence of an incoming noise can be reduced as much as possible, and the outside magnetic field Hext. can be more accurately detected in an extremely simple constitution.
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