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Check transistor

Discussion in 'General Electronics Discussion' started by Avidestroyer, Jan 17, 2013.

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  1. Avidestroyer


    Jan 11, 2013
    How to check a bipolar junction transistor(bjt) that how can I trace what is emitter, collector and base.
  2. duke37


    Jan 9, 2011
    The transistor may be npn or pnp and the polarity will differ.
    Small transistors can be EBC or BCE.
    Big transistors usually have the collector in the centre and it is often connected to a tab for cooling.

    You can use a meter to measure resistance between the leads. The base will be the lead which has approximately the same resistance to the other two leads. It should be low resistance in one direction and high in the other direction. Do not use the lowest resistance range on the meter, this may give enough current to blow a small transistor.

    Compare with a known transistor to determine whether it is npn or pnp.

    Some meters have a transistor test, one way will give a high gain and one way will give a very low gain. This will distinguish between E and C.

    If all else fails, look up the data sheet.
  3. Avidestroyer


    Jan 11, 2013
    Thank you so much
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