OP593 and OP598 Series Phototransistors. The OP593 and OP598 series, from Optek Technology Inc., are a family of NPN silicon phototransistors. They are in dark blue plastic TO-18 equivalent packages. They offer a wide receiving angle in a variety of different sensitivity ranges.. Features of the OP593 and OP598 phototransistors: Through-hole mounting TO-18 equivalent package Dark blue lens Wide receiving angle Operating temperature: -40 to +100 °C