| 摘要 |
PURPOSE:To switch a constant of a reading-out circuit by adding a simple circuit, by switching a read-out demodulation circuit characteristic by switching a resistance value of a differential constant of a differentiation circuit, when reading out the outside periphery of a magnetic disk, and when reading out the inside periphery of the magnetic disk. CONSTITUTION:Transistors 21a, 21b, load resistances 22a, 22b, constant-current sources 23a, 23b, an inductance 13, resistances 14, 15, a differential capacitor 16, and an FET switch 17 are placed, respectively. The FET switch 17 is switched by a control of a microcomputer, etc., by using a specified track of a magnetic disk as a boundary. When the FET switch 17 is turned on, a high frequency characteristic of a differentiation circuit becomes a characteristic being suitable for reading the inside periphery of a full line, and when said switch is off, said characteristic becomes a characteristic being suitable for reading the outside periphery of a dotted line. In this way, a frequency characteristic of a reading-out circuit can be switched by an extremely simple circuit constitution. |
