AM RADIO RECEIVER

PURPOSE:To ensure the tuning operation while the stabilization of a local oscillation frequency is attained by adding an AFC circuit and an AFCON OFF circuit. CONSTITUTION:An output signal of a pin 19 of a stereo demodulator IC is fed to a base of a transistor (TR) Q1, and an emitter output of the TR Q1 becomes an AFC control voltage via a resistor R2. On the other hand, an AFCON OFF circuit 20 is controlled by an output signal from a pin 10 of the IC. That is, in the PLL synchronizing state, an FETQ5 is turned off, the AFC control voltage VA is fed to a diode D 11 in the local oscillation circuit 10 to activate the AFC circuit. On the other hand, when the PLL is unlocked, the FET Q5 is turned on during the unlocked period and succeeding locking operation to inactivate the AFC circuit. Thus, the tuning operation is ensured while the local oscillating frequency is stabilized.