| 摘要 |
PURPOSE:To stabilize bias current at the time of receiving a black and white signal and to eliminate a color noise at the time of receiving the black and white signal by separating the current path of a color signal from a bias current path at the time of receiving the black and white signal. CONSTITUTION:When the color signals V1, V4 of a PAL system and an NTSC system are received, a switch 5 is connected to a bias voltage V2 source 2 side, since V1>V2, the signal V1 is demodulated by transistors(TRs) 18, 19 through a TRr 9, and the signal V4, since V4>V2, is demodulated by TRs 20, 21 through TR 12. At the time of receiving the black and white signal of the PAL system and the NTSC system, the switch 5 is connected to a bias voltage V3 source 3 side, since V3>V1, V4, mutually equal currents are conducted TRs 10, 11 through TRs 13, 14 by the bias voltage V3 and a constant voltage is outputted to the output of a resistance 24.
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