A CMOS-based photosensor array, having a plurality of photodiodes therein, includes a spillover protection circuit associated with each photodiode. The spillover protection circuit causes a potential to be applied to a photodiode in response to a charge spillover or "blooming" condition. The spillover protection device is momentarily disabled whenever a bias charge is injected onto the photodiode by the transfer circuit. Also, a reference voltage applied to the gate of a transistor forming the spillover protection device is higher than a threshold voltage of the transistor but is lower than a sum of the threshold voltage and a maximum light-intensity signal from the photodiode.