General-purpose NPN in a tiny SOT-323
The BC 817K-25W E6433: The Infineon BC 817K-25W is a general-purpose NPN bipolar transistor in a surface-mount SC-70 (SOT-323) package. It handles a collector current up to 500 mA and a collector-emitter breakdown voltage of 45 V.
250 mW power — thermal budget in a small package
With a maximum power dissipation of 250 mW in the SOT-323 body, this transistor is not meant for continuous high-current loads. At 500 mA the Vce saturation is 700 mV, so the on-state power at full current is 350 mW — above the package limit. Practical continuous collector current is derated to roughly 350 mA at 25 °C ambient, and less at elevated temperatures. Use it for switching loads like relay coils, LED drivers, or signal-level amplification where the average dissipation stays under the ceiling.
The BC 817K-25W is listed as Obsolete by Infineon. For BOM lines that call this exact order code, supply is limited to existing stock in the independent distribution channel.