| 摘要 |
<p>PURPOSE:To prevent the influence of noise upon a magnetic head by not only opening a switch on the input side of a motor driver but also stopping the PWM output only in the period when a reproduced envelope signal is obtained from a magnetic head and not only closing this switch but also outputting the PWM output in the other period. CONSTITUTION:Opening/closing of a switch 32 on the input side of a motor driver 18 is controlled by the switch control pulse obtained by 1/2 frequency division of the output of a head switching pulse generating circuit 34. The switch 32 is opened and the operation of PWM generators 21, 23, and 26 is stopped in a period T1 when the reproduced envelope signal is obtained from a head A, but the switch 32 is closed and this operation is executed in a period T2 when this signal is not obtained. At this time, the voltage just before opening of the switch 32 is held by a signal holding part 33, and the driver 18 is controlled by this voltage. A high frequency component included in the PWM wave is propagated in the space and is not mixed in a magnetic head 24 to improve S/N of recording and reproduced signals.</p> |
