| 摘要 |
A video detecting circuit and an intercarrier sound signal generating circuit suited for implementation in an integrated circuit for use in a television receiver, comprising a video intermediate frequency amplifier including a final stage video intermediate frequency transformer, a tuning circuit coupled to the video intermediate frequency amplifier to be tuned to the video intermediate frequency for withdrawing a video intermediate frequency carrier signal, a diode connection coupled to the tuning circuit for pulsing the video intermediate frequency carrier signal, a double balanced synchronous detector responsive to the video intermediate frequency amplifier and the pulsing circuit for synchronous detecting the video intermediate frequency signal for providing a detected video signal, and a double balanced multiplier coupled to receive the primary and secondary signals at the primary and secondary windings of the video intermediate frequency transformer for evaluating the product of the primary and secondary signals for providing a sound intermediate frequency signal. Preferably, a phase shifter is provided in the double balanced multiplier for causing a phase difference of an odd number times the phase of pi /2 between the primary and secondary signals to be applied to the double balanced multiplier.
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