NPN transistor for general-purpose switching and amplification
The Infineon BC817-16B5003 is an NPN bipolar junction transistor in a SOT-23-3 surface-mount package, rated for 45 V collector-emitter breakdown and 500 mA continuous collector current. With a minimum DC current gain of 100 at 100 mA and a transition frequency of 170 MHz, it suits low-to-medium speed switching and linear amplification in power supplies, motor drives, and signal conditioning stages. The 500 mW power dissipation limit and 150°C junction temperature allow operation in compact, thermally constrained boards.
Ratings that define the load and voltage headroom
The 45 V Vce breakdown gives a comfortable margin for 12 V and 24 V rails, but keep derating in mind if the supply sees transients above 40 V. The 500 mA collector current is the absolute maximum — continuous operation at 300 mA to 400 mA leaves headroom for inrush and ripple. Saturation voltage is 700 mV at 50 mA base drive and 500 mA collector current, so confirm base drive current for the load you are switching. The 500 mW power limit in the SOT-23-3 package means the junction temperature climbs fast above 300 mA continuous. If the board runs hot or the transistor is near other heat sources, measure the actual dissipation or step up to a larger package variant.