| 摘要 |
A video signal compensating circuit for a TV/VCR comprising a first amplifier for amplifying TV video signal which is input from a TV video signal input terminal, a second amplifier for amplifying VCR video signal which is input from VCR video signal input terminal, a control signal generator, a switching element, a third amplifier for amplifying the output signal of the switching element, a first photocoupler for outputting a signal proportional to the output signal of the third amplifier, an output amplifier for amplifying and outputting the output signal of the first photocoupler, a second photocoupler which is turned on and off according to the control signal of the control signal generator, and a negative feedback element for varying the emitter output signal of the transistor of the output amplifier according to "ON" or "OFF" of the second photocoupler and then feedbacks negatively to the base of the light receiving transistor of the first photocoupler. The circuit provides TV/VCR with clear pictures by preventing the input of video noise signals according to the frequency differences between the TV video signal and the VCR video signal.
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