Readout design for imagers with non-saturated integrating

GaAs CCD readout circuit in this paper increases the integrating time up to 16 times by increasing the charge readout ability and no worry about degeneration of sensitivity. The readout circuit is composed of a pair of CMI pre-amplifiers, a counting unit, and a CDS, which use 0.35um 2P4M 5V technology. Simulation shows that the integrating time can easily break 250μs when the current flows out from the floating diffusion area of CCD I_det=100nA, current gain A_c=2 and integrating capacitor C_int=2pF. The noise power at the output C_sh node is around 1.08×10^-12 V² by 4 kHz, which equals only 13e^- equivalent noise electrons compared with 3×10⁸e^- full charge readout ability.