| 摘要 |
PURPOSE:To attain suitably the detection of a dropout control signal without being susceptible to the effect of noise, in a video disc player and a video tape recorder, by providing a positive feedback circuit to an output of a limiter amplifier circuit or a comparator circuit. CONSTITUTION:If an RF signal having a dropout part enters the limiter amplifier circuit 2, a part of the output is given to the positive feedback circuit 9 for applying a DC feedback for the purpose of adjustment. Then, the DC oscillation is produced for the part without any RF signal and the output becomes the upper limit state as T3 in Fig. (B), allowing to prevent any distortion and noise at the output of an FM demodulator 3. The noise of the part having dropout becomes an RF signal without noise by applying the positive feedback to the amplified noise at the limiter amplifier circuit 2, and an output (B) of the limiter amplifier circuit 2 is obtained. The misdetection is reduced by applying the output of the limiter amplifier circuit 2 to a frequency detecting circuit 6 for detecting the dropout, in comparison with the detection using a signal having much noise. |
