45 V, 500 mA general-purpose NPN — now obsolete
The Infineon BC817K40WE6327HTSA1 is a general-purpose NPN epitaxial silicon transistor in the SC-70 (SOT-323) surface-mount package. This part is now listed as obsolete by the manufacturer.
What the 45 V breakdown and 500 mA Ic mean for your design
The 45 V Vce breakdown gives comfortable headroom for 24 V and 12 V rails, but the 250 mW power limit in the SC-70 package means the safe operating area is constrained. At 500 mA continuous, Vce(sat) is 700 mV at 50 mA base drive, so the conduction loss in saturation is about 350 mW — above the package's 250 mW rating. For continuous saturation switching, derate the current or pulse the load. The 170 MHz fT is fine for switching up to a few MHz and for audio-frequency amplification.
For BOM lines that still require this exact order code, the remaining stock in the independent distribution channel is the only option. For new designs or long-term production, a pin-compatible alternative in the BC817 family with the same SC-70 footprint should be qualified.