Gain controller using switched capacitors

A gain controller for controlling gain of an analog input signal, said gain controller being operable in a sampling operational mode and an amplifying operational mode, comprising:

• an operational amplifier for controlling the gain of the analog input signal and generating an output signal having the controlled gain, the operational amplifier being operable in a switching mode and having an output which includes first and second output terminals, an output terminal switch being operable to connect the first and second output terminals together when the operational amplifier is in the switching mode;
• input capacitors connected in parallel to the input side of the operational amplifier;
• a feedback capacitor connected between the input side and the output side of the operational amplifier;
• a plurality of switches for selectively connecting at least one of the input capacitors to at least one of the input signal and a reference voltage, in response to the operational mode and an externally applied predetermined digital gain control signal;
• an input which differentially inputs an output of a correlated double sampler (CDS), the CDS sampling and holding a photographed image and providing the sampled and held image as the output of the CDS;
• gain controlling circuitry which controls the gain of the output of the CDS in response to a digital gain control signal, the digital gain control signal being provided by a digital signal processor in response to a digital signal;
• and
• an output which provides a gain-controlled output signal to an analog-to-digital converter which converts the gain-controlled/output signal into the digital signal.