The A42 from Galaxy Century Microelectronics is a Bipolar Junction Transistor with Emitter Base Voltage 5 V, Base Emitter Saturation Voltage 0.9 V, Emitter Cut off Current 0.1 µA, Collector Base Voltage 300 V, Collector Cut off Current 0.25 µA. Tags: Surface Mount, NPN Transistor. More details for A42 can be seen below.