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hfe

Discussion in 'Electronic Basics' started by j van c, Sep 24, 2004.

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  1. j van c

    j van c Guest

    Im my thread "transistors" from 22/9/04 Roger explained me how to determine
    the C and E with the hfe test after determining the B.
    I did a test with a H9012, which is a pnp(diode test).(Black at B measuring
    600 mv versus E en C)
    B,E and C are marked on the transistor. There's no doubt about this.
    The two hfe values are 174 and 41.
    So i took the 174-combination. It's quit the opposite.

    Am i doiing something wrong.
     
  2. Well, that's a strange result.

    Many transistors work equally well even if you reverse the C and E
    connections, but it should work better if you connect it as the
    manufacturer has intended it to be used.

    You could try to use it in a common type of circuit, like a common
    emitter amplifier circuit, and try it both ways and see what works best.

    Maybe this type of test doesn't work so well for that particular type of
    transistor, or maybe it is wrongly marked, I don't know, but that way to
    identify the pins usually works.
     
  3. Well -- you did qualify the claim that the transistor would work
    'equally well', but the differences are very serious. For example,
    the collector breakdown voltage in reverse would likely be much
    much lower for most transsitors. Also, most discrete transistors
    have much lower beta in reverse (however, you can find some that
    have high beta in reverse, which can have significant effect on
    Vce saturation voltage.)

    John
     
  4. I hope this clarifies the issue to "j van c" better than
    what I could give him.

    Thanks.
     
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