| 摘要 |
PURPOSE:To simplify the circuit constitution by providing a voltage level detec tion circuit supervising a gain decision voltage of an AGC amplifier and apply ing the correction by servo information representing the position shift quantity of a magnetic head. CONSTITUTION:A start part of parts A, B of a servo data 15 of a magnetic disk 1 is searched by a motor index signal 13, after a lead-in end time of the AGC amplifier 9 is awaited from the start of the parts A/B of the data 15, the gain decision voltage VAGCA/B is detected by a voltage level detection circuit 18 to obtain servo information representing the position shift of the magnetic head 4. Then a proper correction quantity is operated from the differ ence between the voltages VAGCA and VAGCB, the result is outputted to a servo correction circuit 7, a motor drive circuit 6 drives a stopping motor 5 of a magnetic head positioning mechanism to apply positioning correction. As a result, a read amplifier for a servo motor is not required, the necessity of fixed gain of the AGC amplifier is not required and since the gain decision voltage offers the servo information, the circuit constitution is simplified.
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