The HCPL-4502/HCPL-2503, 6N135/6 and HCPL-2530/HCPL-2531 optocouplers consist of an AlGaAs LED optically coupled to a high speed photodetector transistor. 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 10kV/s. An improved package allows superior insulation permitting a 480 V working voltage compared to industry standard of 220 V.