| 摘要 |
PURPOSE:To eliminate the pop noise that is produced in supplying power source and at a start/cancel of muting action, by giving a slow change to the DC voltage of a DC blocking capacitor for a muting circuit in an amplifying circuit which delivers an output via the blocking capacitor. CONSTITUTION:The 1st transmission gate MISFETQ1 that is controlled by the muting control signal is provided between the output and the DC blocking capacitor C2 of the amplifying circuit 1, along with the serially connected 2nd and 3rd transmission gates MISFETs Q2 and Q3 which are controlled by the signal having the reverse phase to the muting control signal. Then the capacitor C1 is installed between the connection point between the MISFETs Q2 and Q3 and the Ac-type earth terminal. At the same time, the level change is made slow by the muting control signal in the direction where the MISFETQ1 is turned on. |
