A thin-film magnetic head has a lower magnetic pole section including a front portion close to a face of the head opposing a recording medium. The drive device includes an amplifier unit for amplifying a voltage applied to an input to obtain an amplified gradation voltage, and a voltage generation unit for generating the positive polarity gradation voltage and the negative polarity gradation voltage according to the amplified gradation voltage. The method generates a hand wheel angle signal that indicates a position of a hand wheel of the vehicle based on the yaw rate.