For example , Schottky Diode , LED ( Light Emitting Diode ) , Photo Diode , Laser Diode , Varactor Diode , Current Regulator Diode , PIN Diode , Tunnel Diode , Step Recovery Diode , IMPATT Diode , etc. The most common function of a diode is to allow an electric current to pass in one direction ( called the diode 's forward direction ) while blocking current in the opposite direction ( the reverse direction ) . Thus , the diode can be thought of as an electronic version of a check valve .