Patent ID: 8447046

Claim:
A circuit with three-stage of power-on sequence used for suppressing the pop noise in audio system, comprising: a first resistor (R 1 ), having a first end with a voltage of V 1 and a second end with a voltage of V out ; a capacitor (C out ), having a first end electrically connected to the second end with the voltage of V out of the first resistor (R 1 ) and a second end electrically connected to a second resistor (R 2 ); a first switch (SW 1 ), having a first end and a second end electrically connected to the first end with the voltage of V 1 of the first resistor (R 1 ), used for controlling the electronic signal passing or blocking; a second switch (SW 2 ), having a first end and a second end electrically connected to the first end with the voltage of V 1 of the first resistor (R 1 ), used for controlling the electronic signal passing or blocking; a soft start device, having an input end with a voltage of V REF SSD and an output end with a voltage of V o1 electrically connected to the first end of the first switch (SW 1 ), used for providing a specific voltage raised with small steps; a first feedback amplifier, having an operational amplifier (OP 1 ) having a first input end, a second input end with a voltage of V REF OP1 and an output end with a voltage of V O2 , a first resistor (R 3 ) having a first end with a voltage of V in and a second end electrically connected to the second input end of the operational amplifier (OP 1 ), a second resistor (R 4 ) with a first end electrically connected to the first input end of the operational amplifier (OP 1 ) and a second end electrically connected to the output end with the voltage of V O2 of the operational amplifier (OP 1 ); and a second feedback amplifier, having an operational amplifier (OP 2 ) having a first input end, a second input end with a voltage of V REF OP2 and an output end with a voltage of V O3 , a first resistor (R 3 ′) with a first end with a voltage of V in and a second end electrically connected to the second input end of the operational amplifier (OP 2 ), a second resistor (R 4 ′) with a first end electrically connected to the first input end of the operational amplifier (OP 2 ) and a second end electrically connected to the output end with the voltage of V O3 of the operational amplifier (OP 2 ).