| 摘要 |
PURPOSE:To obtain a signal suitable for A/D conversion by applying filter processing to a picture signal during black level clamp period only so as to clamp a signal after filter processing thereby eliminating the reset noise of dummy bit. CONSTITUTION:An output picture signal from a solid-state image pickup element 11 is subjected to impedance conversion by an emitter follower circuit 12 and subjected to filter processing by a filter circuit 21 for a clamp period only, then the clamping for a black level is applied via an AC coupling amplifier circuit 17 and a clamp circuit 18. In this case, the circuit 21 is constituted as a low pass filter comprising a resistor R and a capacitor C and a switching transistor. TrQ is connected between the capacitor C and ground and the same pulse as the clamp pulse controlling the circuit 18 is inputted. Since the clamp pulse goes to an H level during the dummy bit period of the black level, the clamping is applied, the Tr Q is turned on to function the circuit 21. Then the reset noise of the dummy bit is eliminated and a signal suitable for A/D conversion is obtained.
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