| 摘要 |
PURPOSE:To obtain a simple configured and inexpensive video signal detection circuit by constituting to compare a detecting output voltage which is outputted from the AGC detection circuit of an AGC loop circuit in a video tape recorder at a comparator. CONSTITUTION:An AGC detection circuit 12 generates a smoothed signal by detecting the pedestal part and the white peak of a video signal 100 inputted to the AGC circuit 11 and settles the level of a video signal inputted to the AGC detection circuit 12 by controlling the gain of the AGC circuit 11 through this smoothed signal. Hereupon, a comparator 13 compares the detecting output voltage inputted from the AGC detection circuit 12 with a reference voltage and it is detected that there is no input video signal because the output of a video signal detecting signal 500 is suppressed to a low level when the detecting output voltage is higher or lower than the reference voltage. Accordingly the configuration of a circuit is simplified as stated above.
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