| 摘要 |
PURPOSE:To perform less-distortion recording by determining the quantity of negative feedback on the basis of a voltage depending upon the inductance of a head. CONSTITUTION:The gain of an amplifier for detection is r+R/r (R: resistance value of magnetic head), so the voltage across a detection resistance (r) is Ir where I is the head current, and the output voltage of the detection amplifier 12 is (r+R/r)Ir(r+R)I. When a bias trap circuit, etc., are ignored, on the other hand, the voltage of the output stage of a recordint amplifier 5 is I(R+r+ZL), where ZL is the impedance depending the inductance of the head. The impedance ZL becomes larger and larger as the voltage IZL depending upon the inductance and the frequency become higher and higher, and the current I decreases to the contrary, so no frequency characteristic is obtained. A frequency compensating circuit 14, however, is provided, so negative feedback control under which a constant current characteristic to the frequency is obtained is provided. |
