The BC817K-40 from Diotec Semiconductor is a Bipolar Junction Transistor with Emitter Base Voltage 5 V, Base Emitter Saturation Voltage 1.2 V, Emitter Cut off Current 100 nA, Collector Base Voltage 50 V, Collector Cut off Current 100 nA. Tags: Surface Mount, NPN Transistor. More details for BC817K-40 can be seen below.