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How to Hook Up a Transistor

Transistors are semiconductors often used as amplifiers and switches. They have three layers, with a lead attached to each one. The layers are called the base, emitter, and collector. The base, often in the middle, controls the current through the other two. For an NPN transistor, the middle layer is the base, and the emitter and collector sandwich the base. To hook up a transistor, build a common emitter (CE) circuit --- so called because the ground side of each of the power sources connects to the transistor's emitter.

Things You'll Need

Solderless breadboard
100k resistor
Battery holders
1k resistor
3- and 9-volt batteries
Jumper wire
Digital multimeter

Instructions

- 1
  Identify which leads are the base, emitter,and collector on the transistor. You' should find this information on the package, manufacturer's website or data sheet. Some electronics texts also have them in the appendix.
- 2
  Separate the leads of the transistor slowly and carefully. Insert the device into a breadboard, placing each lead into a separate column.
- 3
  Connect a 100k resistor to the same column to which you've connected the base lead. Add the red lead of a 3-volt battery holder to this column. If necessary, use jumper wires. Connect a battery holder's black lead to a separate column on the breadboard, and treat this column as ground, which means zero voltage.
- 4
  Add a 1k resistor to the same column in which you've placed the collector. Connect the red lead of the 9-volt battery holder to the free end of the resistor. Connect the battery holder's black lead to the ground column.
- 5
  Place a jumper wire into the same column in which you've placed the emitter, and attach the wire's other end to the ground column. Insert the batteries into the holders.
- 6
  Measure Vce, the voltage between the collector and the emitter, by holding the probes of a digital multimeter against the collector and emitter legs of the transistor. In the same manner, measure Vbe, the voltage between the emitter and the base. A representative value for Vce is 7.95 volts, though ideally it should be 9 volts --- the battery voltage. A representative value for Vbe is 0.7 volts.

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