| 摘要 |
PURPOSE:To perform an accurate clamping operation without being influenced by noise, to make a large-capacity capacitor unnecessary and to make a device into an integrated circuit by using a switch capacitor provided with the first small-capacity capacitor and the second capacitor whose capacity is sufficiently larger than that of the first capacitor. CONSTITUTION:In a period T1 when a clock signal phi is in the high level, a transistor (TR) 24 is turned on, and an electric charge corresponding to an input signal V1 in the pedestal level is stored in a small-capacity capacitor 25. In a period T2 when a clock signal phi' is in the high level, a TR 26 is turned on, and the capacitor 25 and a capacitor 27 whose capacity is sufficiently larger than that of the capacitor 25 are connected electrically and electric charges matched to respective capacities are distributed to these capacitors. The voltage between both ends of the capacitor 27 is an average value of the pedestal level of the input signal V1. Even if a noise component exists in the pedestal part of the input signal V1 and is held in the capacitor 25, the voltage between both ends of the capacitor 27 is not changed greatly, and the accurate clamping operation is performed. |
