| 摘要 |
PURPOSE:To simplify the adjusting work of frequency characteristic by applying a detected output of a video intermediate frequency amplifier circuit to a peak value detecting circuit and applying automatic gain control to the video intermediate frequency amplifier circuit by the peak value detected output externally. CONSTITUTION:When the output signal S1 of a video detecting circuit is impressed to a terminal 17, a phase polarity inverting circuit 18 outputs an output signal S2 inverting the phase and polarity to an output terminal P1. On the other hand, a gate signal g1 is impressed to a terminal 19 and a transistor (TR) 20 is turned on at a period where a main sweep period and a sub-sweep period are changed over. Then, an output waveform of a buffer amplifier 24 is C. In adjusting each trap point of the video intermediate frequency amplifier circuit, the output signal S3 of the buffer amplifier 24 is inputted to a peak hold circuit 34. Since a signal E obtained at an output P4 of a buffer amplifier 35 is not a complete DC voltage, further one stage of peak hold circuit 40 is prepared so as to obtain a sufficient DC voltage F and a difference between a peak value votage and an adjusting reference voltage is obtained by a differential amplifier 53 and it is used for automatic gain control. |
