08 September 2013

Testing Bipolar Transistors


  1. Obtain a silicon diode, simple analog ohmmeter or DMM, test leads, 100K resistor & mystery bipolar transistor
  2. Set the ohmmeter to a low resistor reading scale
  3. Identify which is the positive lead and which is the negative lead by forward biasing the diode
  4. Identify the Base as the lead on the transistor that is common to the Collector/Emitter in the forward bias condition.
  5. If the Base is negative then it is a PNP transistor. If it is positive then it is NPN.
  6. Take a guess. Connect the test leads to the Emitter/Collector
    1. Forward bias the transistor by connecting the 100k resistor between Base and Collector by guessing which is the Collector. The forward bias condition is seen as the ohmmeter showing a low resistance reading.
    2. For a PNP transistor the Emitter will be connected to the positive lead.
    3. For an NPN transistor the Emitter will be connected to the negative lead

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