ON Semiconductor, MMBTA42LT1G, Transistors, Bipolar (BJT) Transistors

 MMBTA42L Series 300 V 500 mA 225 mW NPN High Voltage Transistor - SOT-23-3

https://www.futureelectronics.com/p/semiconductors--discretes--transistors--bipolar-transistors/mmbta42lt1g-on-semiconductor-8133795