Ultra high sensitivity on-chip amplifier for VLSI CCD image sensor

A novel high-sensitivity on-chip amplifier for CCD (charge coupled device) image sensors is evaluated within a very small signal range of under 20 electrons, which is the photon counting region for highly sensitive imaging devices. Because the output noise of 0.084 mV RMS is smaller than the output voltage/electron of 0.22 mV/electron measured in the larger-signal region, the discrete voltage levels corresponding to numbers of signal electrons were directly observed in an oscilloscope in the small signal region. By this observation, it was confirmed that high responsivity is maintained in the very-small-signal region. Therefore, it is possible to realize a photon-counting solid-state image sensor and a highly sensitive megapixel-level HDTV (high-definition television) imager