An IGBT driver provides the drive voltage to the gate of an IGBT to switch it  “ON” or “OFF”. As an optocoupler, it optically isolates the low voltage control circuitry from a high voltage load like a 3 phase motor. IGBT drivers provide the high output voltage, from 15 V to 32 V, to turn on the IGBT and a low or negative voltage to turn off the IGBT. To do this, the IGBT driver has an emitter and photodetector with an integrated control IC, shown here in orange, which drives the two output transistors Tr1 and Tr2 according to the truth table shown.