| 摘要 |
PURPOSE:To obtain a clamping circuit having a simple constitution by providing a switch circuit whose turning on/off and conduction and resistance are controlled by means of an output from a synchronizing signal detection circuit, and a reference value calculation circuit controlled by means of an output from the synchronizing signal detection circuit. CONSTITUTION:If the synchronizing signal is not detected, the conductive and resistant values of the switch circuit 9 are controlled to prescribed values, and said circuit 9 is continuously closed. The reference value calculation circuit 6 outputs a prescribed constant value and supplies it to the switch circuit 9 through a D/A converter. Thus, a time constant circuit formed with the conductive and resistant values of a capacitor 2 and a switch circuit 9 cuts only the low frequency of the output from a buffer circuit 1. After the synchronizing signal is detected, the reference value calculation circuit 6 supplied the signal to be the reference of the DC level of a reproduction signal and a clamping signal generation circuit 7 closes said circuit 9 for a prescribed period in an input signal. Conduction and resistance of the switch circuit 9 is controlled to such a small value as to have an enough DC reproduction capacity.
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