SIGNAL PROCESSING CIRCUIT, AND DRIVE SYSTEM FOR MOTOR

To remove the output voltage offset of a magnetic sensor that is caused to occur by an external magnetic field.SOLUTION: A signal processing circuit pertaining to the disclosed embodiment amplifies the signal of a magnetic sensor that changes in accordance with the magnitude of a magnetic force. The signal of the magnetic sensor is a complementary signal consisting of a pair of signals which are mutually in reverse to a reference voltage. This signal processing circuit comprises a high-pass filter for applying high-frequency pass processing to a complementary signal from the magnetic sensor, a differential amplifier for accepting the complementary signal subjected to high-frequency pass processing by the high-pass filter as a differential input signal and amplifying the differential input signal with a prescribed rate of amplification based on the reference voltage, and a comparator for outputting a binary signal that indicates the result of comparison of the output signal of the differential amplifier and the reference voltage.SELECTED DRAWING: Figure 5 【課題】外部磁場によって生ずる磁気センサの出力電圧のオフセットを除去する。【解決手段】開示される実施形態に係る信号処理回路は、磁力の大きさに応じて変化する磁気センサの信号を増幅する回路である。磁気センサの信号は、基準電圧に対して互いに反転した一対の信号である相補信号である。この信号処理回路は、磁気センサからの相補信号に対して高域通過処理を施すハイパスフィルタと、ハイパスフィルタによって高域通過処理が施された相補信号を差動入力信号として、基準電圧を基準に所定の増幅率で差動入力信号を増幅する差動増幅器と、差動増幅器の出力信号と基準電圧の比較結果を示す２値の信号を出力する比較器と、を備える。【選択図】図５