Skip to content

Transistor

NPN and PNP transistors and Darlington arrays: BC547, BC557, 2N2222, 2N3906, TIP120, TIP122, D400, C1815 and ULN2803A.

Bipolar transistors in TO-92 and TO-220 packages for switching and amplifying: small-signal NPN (BC547, BC548, 2N2222, C1815, 2SC828A) and PNP (BC557, BC558, 2N3906, 2N5401) types, the D400, TIP120 and TIP122 Darlingtons for heavier loads, the 2N7000 small MOSFET and the ULN2803A eight-channel Darlington array.

Switching a load from a microcontroller

For LEDs, buzzers and small relays, an NPN transistor such as the BC547 or 2N2222 with a base resistor of about 1kΩ is enough. For motors and solenoids use a TIP120 or a logic-level MOSFET, and put a diode across inductive loads. Always check the pinout in the datasheet: it differs between part numbers.

Main Menu