Abstract: A photodetection system includes first and second photodetectors, each having an anode and a cathode. The anode of one of the photodetectors is ohmically connected to the cathode of the other photodetectors. The photodetectors are suitably electrically biased and disposed for receiving one or two light beams. Output circuit means are electrically connected to the anode and cathode junction between the two photodiodes for providing an output electrical signal having low or no common mode noise. A preferred embodiment of the invention using a single semiconductor chip for the entire circuit arrangement is also illustrated.