The HCPL-2200/2219 are optically coupled logic gates that combine a GaAsP LED and an integrated high gain photo detector. The detector has a three state output stage and has a detector threshold with hysteresis. The three state output eliminates the need for a pullup resistor and allows for direct drive of data busses. The hysteresis provides differential mode noise immunity and eliminates the potential for output signal chatter. A superior internal shield on the HCPL-2219 guarantees common mode transient immunity of 2.5 kV/μs at a common mode voltage of 400 volts.