Designed as a miniaturized surface-mount device for infrared detection in sensing applications, OPTEK Technology (Carrollton, TX) has developed a series of NPN silicon phototransistors in 1206 chip packages. The devices are packaged with a flat molded lens; the OP520 features an opaque lens to shield it from ambient light, while the OP521 lens is water clear, giving it a wider response range. The devices exhibit response times of 15 μs with peak response to 880-nm light. Electrical performance of the OP520/521 Series is characterized by collector-emitter voltages of 30 V, emitter-collector voltage of 5 V, collector current of 20 mA and power dissipation of 75 mW at 25 °C. They are RoHS-compliant and are compatible with high-temperature (260 °C), lead-free soldering processes. Rated for operation from -25 °C to +85 °C, the phototransistors are designed to be mechanically and spectrally matched to OPTEK’s OP250 series surface mount infrared LEDs.