TEFT4300 Series Phototransistor. The TEFT4300 series, from Vishay Semiconductor, are silicon NPN phototransistors. They come in standard 3mm (T-1) through-hole packages. A black plastic package provides daylight blocking filter for ambient visible light. The TEFT4300 is ideal for applications such as optical switches, counters and sorters, interrupters, encoders and position sensors.. Features of the TEFT4300 phototransistors: 3mm (T-1) package Through-hole mounting Black plastic package Daylight filter High radiant sensitivity Fast response times Angle of half intensity: 30° Operating temperature: -40 to +100 °C