Saturday, November 9, 2013
AN7415 FM Stereo Demodulator
The circuit shown is a stereo FM PLL demodulator designed based on the AN7415. C1 is the input coupling capacitor to block any DC voltage present on the multiplexed input signal. LED D1 is an LED and R1 is the current limiting resistor. C4 and C5 are DC decoupling capacitors to the output channels left and right. C2 and C3 are bypass capacitors for noise output channels left and right. POT R2 can be used to adjust the separation between channels.
The resistor R5 and capacitors C7 and C8 form a network of low-pass filter for the internal DC amplifier circuit (see block diagram AN7415). C10 is a filter capacitor for the internal amplifier circuit Schmitt trigger IC. C9 is a filter capacitor for the circuit wave surge inside the AN7415. Resistor R3, R4 and capacitor C6 POT set the time constant of internal VCO circuit. Therefore POT R4 can be used to adjust the frequency of the VCO. A control signal 19KHz frequency is available in 12 pin IC. The switch S1 can be used to activate and deactivate the forced mono.
The resistor R5 and capacitors C7 and C8 form a network of low-pass filter for the internal DC amplifier circuit (see block diagram AN7415). C10 is a filter capacitor for the internal amplifier circuit Schmitt trigger IC. C9 is a filter capacitor for the circuit wave surge inside the AN7415. Resistor R3, R4 and capacitor C6 POT set the time constant of internal VCO circuit. Therefore POT R4 can be used to adjust the frequency of the VCO. A control signal 19KHz frequency is available in 12 pin IC. The switch S1 can be used to activate and deactivate the forced mono.
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