| 摘要 |
PURPOSE:To decrease the number of component parts of an IC, by using a rectifying circuit for automatic gain control in a recording mode also for DC feedback in a reproduction mode. CONSTITUTION:In a recording mode, the signal applied to an input terminal 17 is amplified by a recording amplifier 8, a switch 4 and an output amplifier 5 via a variable attenuator 7 and then monitored at an output terminal 16. This signal is also supplied to a head 1 via a record peaking amplifier 9. As a switch 26 cuts off a transistor TR23, an LP filter/rectifying circuit 35 functions as a rectifier. The DC voltage proportional to the signal amplitude of an output terminal 16 is produced at a terminal 28, and the circuit 35 functions as an automatic gain controller. In a reproduction mode, the signal reproduced by the head 1 is reproduced in a normal way. The TR23 conducts by the switch 26, and the circuit 35 functions as an LP filter. Then the DC fluctuation component of the output terminal 16 is fed back negatively to a reproducing amplifier 3. |
