Abstract: In a CCD imager, a charge is accumulated in pixels of an image area representative of the intensity of incident radiation and is subsequently transferred to a store section and then on a row by row basis to an output register by applying suitable drive pulses to drive electrodes. Signal charge in the output register is transferred to a multiplication register by drive pulses applied to drive electrodes to give charge transfer in the direction shown by the arrows. One or more drive pulses applied to the electrodes of the multiplication register are of sufficiently large amplitude to produce high field regions in the register element to cause signal multiplication by impact ionisation. This gives a low noise amplification of the signal charge, the multiplied signal charge being detected at charge detection circuit.