The FOD050L and FOD053L optocouplers consist of an AlGaAs LED optically coupled to a high speed photodetector transistor. These devices are specified for operation at a 3.3 V supply voltage. A separate connection for the bias of the photodiode improves the speed by several orders of magnitude over conventional phototransistor optocouplers by reducing the base-collector capacitance of the input transistor.. An internal noise shield provides superior common mode rejection of CMH = 50 kV/μs (typical) and CML = 35 kV/μs (typical).