General-purpose NPN in a small SOT-323 package
The Infineon BC817K16WH6327XTSA1 is a 45 V, 500 mA NPN epitaxial planar transistor in the SC-70 / SOT-323 surface-mount package. It is a general-purpose switching and amplification device — the kind you find in load drivers, relay coils, small-signal preamp stages, and level shifters on 12 V or 24 V rails. The '16' gain group guarantees a minimum DC current gain (hFE) of 100 at 100 mA collector current and 1 V VCE, which means consistent base drive requirements across the reel.
45 V breakdown and 500 mA collector current — where it fits
The 45 V VCEO breakdown covers 12 V and 24 V industrial rails with margin, but it is tight for 48 V systems — derate or move to a 60 V or 80 V part. The 500 mA continuous collector current handles solenoid drivers, small relays, and LED strings; the 250 mW power limit in the SOT-323 package is the real constraint. At 500 mA the VCE(sat) is 700 mV max at 50 mA base drive, so junction temperature climbs fast if you run near the current limit in a warm enclosure.
170 MHz transition frequency — switching speed context
The 170 MHz fT is typical for a medium-speed NPN in this package class. It is fast enough for 1–10 MHz DC-DC converter gate drivers, relay coil snubbing, and audio-frequency amplification, but not for RF front-ends or high-speed digital logic. The 100 nA max collector cutoff current (ICBO) is low enough that leakage in high-impedance bias networks is not a concern at room temperature; budget for the 150°C junction temperature rating if the part sits near a heat source.
Infineon lists this exact variant as Last Buy. If your BOM calls out this exact suffix, you are now sourcing from the surplus and broker market, where date-code consistency and traceability matter. The BC817-16 in a more common package (SOT-23) is the functional equivalent for new designs that can accommodate the larger footprint.