| 摘要 |
PURPOSE:To simplify the circuit constitution of a magnetic erasing device for miniaturization together with high reliability, by using a magnetic head for recording, reproduction and erasing properly with switching through the ON/OFF operations of a semiconductor switch and the control of a DC constant current source carried out by a current mirror. CONSTITUTION:The reference current I0, i.e., a DC current which is reduced gradually is produced by a current/voltage conversion circuit II with input of an erasion command 10 of a terminal A. Then the current I0 flows to a reference transistor Tr3 of a switch over circuit III. Here both Tr6 and Tr7 are turned on and off alternately for each switch of polarity by a switch control circuit V. Then the collector currents I1 and I2 equal to the current I0 flow alternately owing to the current mirror effect. Thus an erasion current flows to a coil 4 of a magnetic head 3 for execution of erasion. While no current I0, I1 nor I2 are produced with input of a recording/reproducing command 11 of the terminal A and both Tr6 and Tr7 are turned on by a switch control command. Then the recording and reproducing signals are transferred via a recording/reproducing amplifier 13 and a transformer 12. Thus the recording and reproducing actions are carried out.
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