800 nm phototransistor — 32 V, 30 mA switching ceiling
The RPT-38PB3F is a top-view NPN phototransistor from ROHM Semiconductor, sensitive at 800 nm and housed in a T1 through-hole package. It is designed for optical sensing in industrial and consumer systems where a discrete photodetector with a moderate switching current is needed. Rated for a supply voltage up to 32 V and a switching current of 30 mA, the device can drive logic inputs or small relays directly without a separate amplifier stage. The 72° viewing angle provides a wide acceptance cone, simplifying alignment in through-beam or reflective sensor assemblies.
Temperature grade and operating envelope
The RPT-38PB3F is specified over -25°C to 85°C ambient, a standard industrial temperature range. The 0.15 W power dissipation limit governs the collector current under continuous illumination — at 32 V bias the maximum steady-state collector current is approximately 4.7 mA before exceeding the dissipation ceiling. The 800 nm peak sensitivity matches common infrared LEDs (e.g., 850 nm or 940 nm emitters) with good responsivity. The top-view orientation means the lens faces upward when the leads are inserted through the PCB, suited for edge-mounted or panel-mounted sensor windows.