  We introduce a new output amplifier for fully-depleted thick p-channel CCDs
based on double-gate MOSFETs. The charge amplifier is an n-type MOSFET
specifically designed and operated to couple the fully-depleted CCD with high
charge-transfer efficiency. The junction coupling between the CCD and MOSFET
channels has enabled high sensitivity, demonstrating sub-electron readout noise
in one pixel charge measurement. We have also demonstrated the non-destructive
readout capability of the device. Achieving single-electron and single-photon
per pixel counting in the entire CCD pixel array has been made possible through
the averaging of a small number of samples. We have demonstrated fully-depleted
CCD readout with better performance than the floating diffusion and floating
gate amplifiers available today, in both single and multisampling regimes,
boasting at least six times the speed of floating gate amplifiers.
