| 摘要 |
PURPOSE:To ensure the dynamic range while reducing power consumption by controlling a power current to an amplifier circuit of an amplifier circuit of a reception signal in response to a line current. CONSTITUTION:A smoothing circuit 71 smooths a line current of a telephone line and its output voltage changes corresponding to the line current. A logic circuit 64 outputs a prescribed constant voltage signal from terminals 5, 6 corresponding to a control signal of terminals 9, 10 and a prescribed constant current flows from a current circuit 74. The constant current is supplied to an amplifier circuit 73 as a power supply current via an NPN transistor 58 acting like the supply circuit via a current mirror circuit 72. Thus, when the line current is increased, the power current is also increased and the dynamic range of an amplifier circuit 73 is increased. |
