Active NPN transistor in a common SOT-23 footprint
The MMBT3904LT3XT is an NPN general-purpose transistor rated for 200 mA continuous collector current and 40 V collector-emitter breakdown, with a minimum DC current gain of 100 at 10 mA collector current and 1 V Vce. It comes in the TO-236-3 / SC-59 / SOT-23-3 surface-mount package, supplied on Tape & Reel. The 300 MHz transition frequency makes it usable for small-signal amplification and switching up through VHF, while the 330 mW power dissipation ceiling suits low-to-moderate power stages in compact designs.
Saturation voltage and gain — what they mean for a driver stage
The 50 nA collector cutoff current keeps off-state leakage negligible in battery-powered circuits. The minimum hFE of 100 at 10 mA / 1 V gives enough current gain to switch a 200 mA load from a 2 mA base drive — a standard GPIO pin can handle that directly.