The BC109B from Central Semiconductor is a Bipolar Junction Transistor with Emitter Base Voltage 5 V, Base Emitter Saturation Voltage 0.7 to 1.05 V, Collector Base Voltage 30 V, Collector Cut off Current 4 µA, Collector Emitter Breakdown Voltage 25 V. Tags: Through Hole, NPN Transistor. More details for BC109B can be seen below.