Basic Info

  • Transistor_picThe transistor is a type of electrical switch. They are great for using a low-voltage low-current control device, such as a microcontroller or a single-board computer, to drive a device that draws  much more current from an external source, such as a DC motor being externally powered  by four AA batteries or a 9V battery.
  • There are a number of different types of transistors, based on their sensitivity and semiconductor makeup. Some are quite large and require heat sinks to be attached. Transistors are the key component in computers–modern microprocessors can have over 100 million of them!
  • There’s three different leads on most bipolar-junction transistors. The center one, the base, receives an electrical signal that turns the transistor on or off. With the rounded side facing toward you, the lead on the left is the collector, and takes the input of whatever larger current you’re switching. The lead on the right, the emitter, is the output of the switch, and is usually connected to ground.
  • Here’s how a transistor works. Basically, current is allowed to pass from the collector to the emitter only when the base gets a signal (i.e. current). You can imagine it as a gate; the transistor only allows the gate to be open when the base has a current on it.

    Transistor schematic symbol.