STEREO NOISE REDUCTION CIRCUIT IN FM STEREO

摘要

PURPOSE:To reduce multi-path noise by providing a V-I convertion section comparing the 2nd current value corresponding to a negative ripple component with the 1st current value and outputting a current equal to the 2nd current value exceeding the 1st current value. CONSTITUTION:If a ripple component such as a multi-path takes place in an S meter output voltage, it is subject to voltage-current conversion at the V-I converter 6 through a non-inverting amplifier 5. Since the multi-path component has a negative ripple component mainly, the non-inverting amplifier 5 is an amplifier responding to the negative ripple component and consists of a differential amplifier. Then the value is compared with a current set by a resistor R8 and only when the current corresponding to the output of the non inverting amplifier 5 is larger than the setting current, a voltage-current conversion is applied as a dead band. Then the charge/discharge control circuit 7 generates a negative voltage proportional to the ripple component of the multi-path component. The voltage inputted to a DC input section 3 is lowered corresponding to the discharge of the capacitor C by the ripple component such as multi-path and the result is sent to a DC output section 2.