Importance

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Abstract

An actively driven, metal light shield for shielding floating diffusion regions and amplifiers of multi-port CCD or CMOS imager arrays from unwanted light is disclosed. The driven shield overlies one or more floating diffusion regions and buffer amplifiers lying outside the active pixel area of the imager (non-imaging area), which is also protected from unwanted light by a fixed potential shield. The driven shield is directly electrically connected to a source node of a source-follower amplifier stage, i.e., the buffer amplifiers non-inverting output. The fixed potential shield is electrically connected to a DC voltage capable of eliminating charging of the fixed potential shield and substantially overlies the non-imaging area and at least partially overlapping the driven shield. The voltage on the source-follower output follows the voltage impressed on the floating diffusion region capacitance which then drives the driven shield, thereby reducing parasitic capacitance added by the fixed potential shield to floating diffusion regions by about an order of magnitude, which improves the ratio of output voltage of the floating diffusion regions to applied charge. Separate driven shields can also be applied to subsequent stages of source follower amplifiers to reduce parasitic capacitance induced by the fixed potential shield.

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First Claim