| 摘要 |
PURPOSE:To prevent malfunction even under a high gain, by setting the gain of an operation amplifier circuit on a constant level regardless of the level of a reproduced control signal. CONSTITUTION:A reproduced control signal is supplied to an input terminal of an operational amplifier circuit 3 to which a reference bias VB is applied via a capacitor C3 to obtain a positive phase output. The output of the circuit 3 is applied to an input terminal of a peak holding circuit 5 via a clipping circuit 4 which receives application of the bias VB through its input terminal of one side. At the same time, the output of the circuit 3 is applied to the input terminal of one side of a comparing/detecting circuit 6. The output of the circuit 5 is applied to the input terminal of the other side to obtain a short pulse output compared with the output of the circuit 6, i.e., the output of a reproducing circuit for a control signal. This can set the gain of an amplifying circuit on a constant level to prevent malfunction even under a high gain. |
