| 摘要 |
An AFC circuit is employed in a television signal receiving apparatus which comprises a tuner having a local oscillator and a mixer for mixing a received high-frequency video signal and an output local oscillation frequency signal of the local oscillator so to frequency-convert the received high-frequency television signal to an intermediate frequency signal, and a tuning voltage generating circuit for generating a tuning voltage responsive to a desired receiving channel which is selected so as to apply the tuning voltage to the local oscillator of the tuner. The AFC circuit comprises a frequency discriminating circuit for frequency-discriminating an output intermediate frequency signal of the tuner, a lowpass filter supplied with an output signal of the frequency discriminating circuit, and a limiter circuit supplied with an output signal of the lowpass filter, for limiting the voltage level of the output signal of the lowpass filter depending on the desired receiving channel. The local oscillator receives an output signal of the limiter circuit. The limiter circuit performs a limiting operation in each receiving band when receiving a channel in which a change in the local oscillation frequency is large with respect to a change in the tuning voltage.
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