| 摘要 |
PURPOSE:To detect stably the noise level without increasing the number of pins led out externally from a noise detecting circuit, by providing a level shift circuit, the 2nd noise detecting circuit and a noise cancellor for the post-stage of a synchronizing signal amplifier. CONSTITUTION:The pre-stage of the synchronizing signal amplifier 18 is provided with the 1st noise detecting circuit comprising the 1st noise detecting differential amplifiers 11, 12 and the 1st noise detecting circuit output transistor (TR) 15 and the like. Further, the post-stage of the amplifier 18 is provided with a level detecting circuit 35 and the 2nd noise detecting circuit comprising the 2nd noise cancellor TR40, the 2nd noise detecting differential amplifiers 37, 38 and the 2nd noise detecting circuit output TR33 and the like. Moreover, the pins led out externally and input terminal 3 for the noise detecting circuit and the synchronizing signal amplifier, a synchronizing separating capacitor and resistor connecting terminal 25, a synchronizing separating output terminal 29, and a power supply voltage applying terminal 31 in total four, and the detection of the noise level is done stably without increasing the number of pins. |
