A four transistor CMOS active pixel sensor with high dynamic range operation

A new CMOS APS using standard CMOS logic technology is proposed to allow high dynamic range operation. The new cell is constructed by incorporating one additional transistor to the conventional three transistor APS. The experimental results demonstrate that extended dynamic range is obtained when operates with a ramped reference voltage source. The cell offers flexible nonlinear transfer characteristics, which can be designed by modifying the operational timing diagram. Furthermore, charge collection on the parasitic capacitor allows for the use of the signal due to hole accumulation. An alternative operation of this cell is also proposed to provide enhanced characteristics in both its sensitivity and dynamic range.