Patent ID: 8891787

Claim:
A POP noise suppressing circuit, for an audio system, comprising a blocking capacitor and an outputting element connected to said blocking capacitor, a current generating unit, a charging unit connected to said current generating unit, a discharging unit connected to said current generating unit, a switching unit connected to said charging unit and said discharging unit and a power amplifying unit connected between said switching unit and said blocking capacitor, wherein said current generating unit provides two slowly increasing currents respectively to said charging unit and said discharging unit; said switching unit is for switching between said charging unit and said discharging unit; a charging current which firstly increases slowly and smoothly and then decreases slowly and smoothly is formed in said charging unit; a discharging current which increases slowly and smoothly and then decreases slowly and smoothly is formed in said discharging unit; a voltage of said blocking capacitor increases smoothly when the audio system is powered on and decreases smoothly when the audio system is powered off; and wherein said current generating unit comprises a third field-effect transistor (FET), a fourth FET, a fifth FET, a sixth FET, a seventh FET, an eighth FET, a ninth FET, a referential current source, a first resistance and a first capacitor, wherein a first terminal of said referential current source is connected to a gate electrode and a source electrode of said third FET and a gate electrode of said fourth FET; a second terminal of said referential current source is connected to earth; a source electrode of said fourth FET is connected to a drain electrode of said ninth FET, a gate electrode of said eighth FET and a positive terminal of said first capacitor; a drain electrode of said eighth FET, a gate electrode and a source electrode of said fifth FET, a gate electrode of said sixth FET and a gate electrode of said seventh FET are all connected with each other.