The ELS511 series devices each consist of an infrared emitting diode, optically coupled to a high speed photo detector transistor. A separate connection for the photodiode bias and output-transistor collector increase the speed by several orders of magnitude over conventional phototransistor couplers by reducing the base-collector capacitance of the input transistor. The ELS611 series devices are consists of an infrared emitting diode optically coupled to a high speed
integrated photo detector logic gate with a st ora ble output. The devices in a 6-pin small DIP package.