A new concept of circuit structure of FPA multiplexer is proposed here, which incorporates an additional MOS switch and a charge-storage capacitor into each pixel of the conventional circuit. The MOS switches are actuated with a high frequency pixel clock, thus enabling the photoexcited charges in each detector to be shared and shielded by the individual storage capacitor. The action of the charge sharing has been analyzed in close form and been simulated by SPICE program. It shows that the saturation capacity indeed can be enhanced. The technique therefore can provide a longer integration time and an additional electronic iris function by controlling the pixel-clock behavior.