| 摘要 |
PURPOSE:To obtain a less-variation detected value by connecting the base and collector of one transistor (TR) in a differential amplifier together through a diode, and using the other TR for detecting the current value of the former TR. CONSTITUTION:A current from a composite video signal voltage source 1 having the same polarity with the synchronizing signal of a television receiver is received by the differential amplifier consisting of TRs 3' and 3'' connected mutually at the bases. The TR3' is diode-connected so that it turns on only at a peak part of the synchronizing signal; currents having the same value are flowed from the TR3' and TR3'' to a C5 and those currents are converted by a resistance 10' into a voltage to obtain a synchronizing peak waveform. A TR61, resistances 62-64, a diode 65 constitute a discharging current source for the C5. The resistance value as the resistance 10' is set large regardless of the turn- on level of the TR3' and its voltage value has less variance. A noise exceeding the synchronizing peak is amplified by differential amplifiers 13 and 14 to obtain only a noise output at an output terminal 17. |
