The HN4C51J from Toshiba is a Bipolar Junction Transistor with Emitter Base Voltage 5 V, Emitter Cut off Current 0.1 µA, Collector Base Voltage 120 V, Collector Cut off Current 0.1 µA, Collector Emitter Voltage 120 V. Tags: Surface Mount, NPN Transistor. More details for HN4C51J can be seen below.