| 摘要 |
PURPOSE:To extract a synchronizing signal securely by stepping down the peak holding output of a means which holds the negative peak value of a video signal at a fixed ratio, and comparing the step-down output with a video output. CONSTITUTION:The video signal Vin inputted to an input terminal M1 is passed through a capacitor C1 to remove its DC component and is inputted to an amplifier A1. The amplifier A1 inverts the signal voltage and applies to a transistor TR1, and a capacitor C2 holds the peak value of the positive voltage of an emitter output. The charge in this capacitor C2 is discharged properly through a resistance R3, but a voltage V2 is applied to an inverting amplifier A2 having a <=1 gain to obtain an output voltage V3. This voltage V3 is applied to the uninverted input terminal of a comparator CM1 and compared with a signal voltage V1 to separate and extract a horizontal synchronizing signal HD. |
