| 摘要 |
PURPOSE:To attain the circuit constitution suitable for an integrated circuit, by sampling and holding a voltage representing a back level with a capacitor and comparing this voltage with a luminance signal at a differential amplifier. CONSTITUTION:When a luminance signal Sy given to a terminal T1 is at a black level, it is applied to a capacitor C1 through a terminal T1, a transistor (TR) Q11, a resistor R11, a TR Q12, and a signal line of the capacitor C1, and the capacitor C1 is charged up to the black level of the signal Sy. When the signal Sy is not at the black level, the TR Q12 is turned off and the capacitor C1 is not charged. A voltage of the capacitor C1 is compared with the luminance signal Sy at a differential amplifier A1 and a luminance signal where the black level is clamped to a prescribed level is extracted at terminals T2 and T3. |
