| 摘要 |
<p>PURPOSE:To fix the DC level of an output terminal by supplying a bias to a current output type amplifier circuit which amplifies control signals in accordance with readout and write pulses and impressing a voltage across the output terminal of the amplifier circuit through a resistance. CONSTITUTION:A fixed voltage is applied across the output terminal 16 of a current output type amplifier circuit 15 constituted of bipolar transistors through a resistance 18 and a bias is caused to be supplied to the amplifier circuit 15 at the time of reproducing control (CTL) signals. Then CTL signals from a CTL head 9 are impressed upon transistors 12 and 13 respectively through bases of transistors 10 and 11. As a result, electric currents corresponding to the CTL signals are made to flow to the collectors of the transistors 12 and 13 and the difference current of the two currents is produced at the output terminal 16. The amplified CTL signals are led to an output terminal 39 after they are impressed and further amplified. Therefore, the DC level of the output terminal 39 can be fixed regardless of the switching operations between readout and writing.</p> |
