| 摘要 |
PURPOSE:To always keep the high reading quality and to improve both the yield and the lifetime of an MR head by using a means to detect the up/down amplitude of a reproduction waveform, a means to extract the difference voltage between detected upper and lower amplitudes and a means to control the external current value to minimize said difference in voltage. CONSTITUTION:A voltage difference detecting circuit 12 using an operational amplifier supplies the envelope voltages of both positive and negative polarity sides and produces the voltage difference between both voltages to the output. This voltage difference is digitized and sent to a microprocessor 14. The processor 14 can know the difference between upper and lower amplitudes of a reproduction waveform with a signal and then transmits a signal indicating the current value to a register 15 under the proper conditions and based on the prescribed judgement. The current value set to the register 15 is transferred to a D/A converter 16 under the control of the processor 14 and converted into the voltage. This voltage is applied to the base of a current source transistor 2, and the current value to be given to an MR head is varied with the change of said voltage. This current value is previously set at such a level that minimizes the difference between the upper and lower amplitudes. Thus, the waveform distortion can be minimized. |
