| 摘要 |
PURPOSE:To improve the S/N ratio of a screen by providing an attenuator connected to the 1st terminal, the 1st amplifier which amplifies its output, the 2nd amplifier which amplifies a signal applid to the 2nd terminal, and a circuit which switches the outputs of both the amplifiers. CONSTITUTION:A normal television signal is inputted to an input terminal 22 and then led to one input of a switching circuit 27 through an attenuator 23 and an amplifier 24. An external primary-color signal, on the ther hand, is applied to a terminal 25 and then led to the other input of the switching circuit 27 through an amplifier 26. The output 28 of the switching circuit 27 is connected to an output amplifier. The attenuator 23 has its attenuation ratio set so that the signal from the terminal 22 has amplitude equal to that of the external primary-color signal applied to the termial 25. Consequently, leakage of carrier components is reduced by the attenuator 23 according to a picture signal, so deterioration in the S/N ratio of a screen is evaded. |
