Clamp signal generating method and clamp signal generator

摘要

PPROBLEM TO BE SOLVED: To provide a clamp circuit which is suitable for a combination with a current-output solid-state imaging element. PSOLUTION: A current signal detection unit 5 performs a CDS process in a current mode to an image signal in the current mode outputted from a solid-state imaging element 3 to suppress an FPN noise, a variable gain amplifier 200 amplifies an imaging signal S0 outputted from the current signal detection unit 5 to a predetermined level, and a current voltage conversion unit 220 converts the imaging signal S0 into a voltage signal S3. In a clamp circuit 250 having a current-output differential amplifier 252 and a current summing unit 280; the differential amplifier 252 compares the voltage signal S3 with a reference voltage from a reference voltage source 290, and feeds back a clamp current Scp to a current summing unit 280 so that a difference voltage is zero. Since a current type clamp circuit is configured with these circuits, a simple configuration in which a signal current S1 is simply added to the clamp current Scp can be applied for the current summing unit 280. PCOPYRIGHT: (C)2007,JPO&INPIT