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about hFE multimeter test...

Discussion in 'Electronic Basics' started by ArameFarpado, Apr 19, 2008.

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  1. ArameFarpado

    ArameFarpado Guest

    Hi all...

    a transistor "BD435" is giving me 440 in hFE test on the multimeter, when
    the tecnical data i've found tell me min=40 max=475...

    does this mean the transistor is really in good shape?
    can it be busted and still give a good hFE test result on the multimeter?

    thanks
    ArameFarpado
     
  2. Not necessarily. The hFE will vary for each transistor depending on IC
    (Collector Current). So for the same transistor the hFE will vary depending
    on what collector current you drive through it. So the range of hFE they
    give is probably not so much an indictation of manufacturing tolerance (this
    transistor is better than that one) but more an indication that ant
    transistor will vary depending on how you drive it.

    Of course there are manufacturing tolerances aswell so the range is a
    combination of the two.

    The tester probably uses a low IC which will lead to a high hFE. If in your
    application you drive IC to say 1A you would probably find the hFE for your
    transistor would drop down low.

    Cheers,

    Nigel
     
  3. ArameFarpado

    ArameFarpado Guest

    Thanks.

    i've just made a strange descovery:
    if i leave the base pin not connected, the hFE result is the same.

    so i guess this hFE test is not for checking if the transistor is fine or
    busted.

    thanks again
    ArameFarpado



    Em Sábado, 19 de Abril de 2008 11:06, Nigel Heather escreveu:
     
  4. Phil Allison

    Phil Allison Guest

    "ArameFarpado"
    ** You have it connected wrong or it is a dud.


    ...... Phil
     
  5. Phil Allison

    Phil Allison Guest

    "ArameFarpado"

    ** You have it connected wrong or it is a dud.


    ** You have it connected wrong or it is a dud.

    Connect a good device correctly and the Hfe reading wil be in the order of
    50 - 150.



    ........ Phil
     
  6. ArameFarpado

    ArameFarpado Guest

    Em Sábado, 19 de Abril de 2008 23:30, Charles escreveu:
    got it, thanks
     
  7. neon

    neon

    1,325
    0
    Oct 21, 2006
    Hfe is an impirical number it actauly means nothing not until it is used in an application.The tester tells as usual that it is good or bad. now here the thing that you must know it does not tells how good it is or how bad it is. It is just an indicator.
     
  8. ArameFarpado

    ArameFarpado Guest

    Em Sábado, 19 de Abril de 2008 23:30, Charles escreveu:
    busted transistor !
    replaced and the circuit started to work...


    thanks again
     
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