| 摘要 |
PURPOSE:To prevent the generation of shock noise when a stand-by function is turned off again by using the drop of the potential of a ripple capacitor to stop the driving of a transistor (TR). CONSTITUTION:When the electric potential of a node between resistors 2, 3 is dropped down to VF or less due to the voltage drop of a terminal 1, TRs 4, 13 are turned off and current from a TR 5 to a bias is cut off. A TR 15 is turned on by the electrostatic charge of a capacitor 12, and while discharging the charge of the capacitor 12 in a ripple filter, the TR 15 supplies the discharged current to the base of a TR 16 to drive the TR 16. The TR 16 discharges an output coupling capacitor C17 to turn the DC voltage of the output terminal to '0'. When the C12 is discharged and the potential of the ripple filter terminal is dropped down to <=3VF, the TRs 14-16 are successively turned off and the complete stand-by state is obtained.
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