In an image sensor having a plurality of photodiodes, subsets of photodiodes share a common node for signals to be sent to an amplifier. Within each subset, each individual photodiode is selected for sending signals to the amplifier by an associated selection device. The selection device is a MOS device operating in a linear region. The subset of photodiodes share a common "fill and spill" or "bucket brigade" transfer circuit to the amplifier, the transfer circuit including at least one MOS device which operates in a subthreshold region.