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Thread: Transistor question

  1. #1
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    Transistor question

    I was reading on this site Troubleshooting & Repair Guide
    Section 5.1

    In the most general of terms, with any bipolar transistor (FETs and MOSFETs are completely different!), there should be about 600-700mV measured between the emitter and base

    Am I correct in understanding one probe on emitter and one on base?

    Thanks,

    nosaj

  2. #2
    g1
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    Yes that is correct. And the polarity of 'which probe where' will be determined by whether it is NPN or PNP.
    Reversed will measure 'OL' or equivalent, forward will measure any where from mid 400's to mid 700's in my experience.
    Certified Dotard

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    I have an old 'note' that I saved that Fahey said a while back. I'm still no transistor master so I save it for reference. Hope it helps

    Universal "expected voltage rules"
    a) a base must be some 600/700mV more positive than the emitter for NPN, negative in PNP.
    b) a collector must be at least 2V more positive than the emitter for NPN, negative in PNP
    that's it

  4. #4
    Old Timer olddawg's Avatar
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    .6-.7v for a foreword biased emitter/base junction for a SILICON transistor.

    .3-.4v for a foreword biased emitter/base junction for a GERMAINIUM transistor.

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