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Transistor - NPN

Created on: 30 July 2012

There are two types of Bipolar Junction Transistors (BJTs), namely, NPN and PNP. Here we look at the NPN transistor used in the tutorials.

NPN Transistor Symbol

The NPN transistor symbol used in circuit diagrams is shown on the left in the diagram below. The NPN transistor symbol has an arrow pointing out. The PNP symbol has an arrow pointing in.

NPN and PNP transistor symbols
NPN and PNP Transistor Symbols

BJT transistors have three terminals called emitter (e), base (b) and collector (c).

Transistor Pinout

Pinout in electronics refers to the mapping of pins from the component's symbol to its physical pins, or location and names of the component's pins.

You will need to find the pinout for each different transistor that you use. Pinouts for some NPN transistors used in the tutorials are shown below:

PN2222 pinout
PN2222 and KSP2222 Transistor Pinout
2N2222 transistor pinout
2N2222, BC107, BC108 and BC109 Transistor Pinout