David Hook

A transistor is a component that works as a current amplifier or a switch.  When used as an amplifier, a small amount of current at one end produces a large amount of current between the other two terminals. When used as a switch, a small amount of current at one terminal opens up a gate for current to flow between two other terminals.

NPN transistors (like our NPN Transistor module) typically have three terminals:

  • Base – your sort of “control” voltage. Current applied here affects what happens between the other two.
  • Collector and Emitter – based on the input from your base terminal, current will flow from the collector to the emitter (essentially the output); Note that in some cases current can flow in reverse as well.
Photo of Circuit Scribe NPN transistor module

Circuit Scribe NPN Transistor module

To learn more about transistors, SparkFun has a great overview, and ExplainThatStuff also has a good primer.