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different hfe's on these transistors

Discussion in 'Electronic Basics' started by Johan Wagener, May 7, 2004.

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  1. I bought the following transistors for an amplifier project. 2N5416
    and 2N3440 made by CDIL.

    I checked their hfe's and had the following result:

    All the 2N5416's have hfe of 100 except one which had hfe of 66.

    2N3440's had hfe's of about 69-72 except one which had a hfe of 58.

    Is this ok?

    Is the hfe of these transistors high enough? I checked the datasheets
    and the specify hfe's of 40-160 for 2N3440 and 30-150 of 2N5415

    Can I use transistors with different hfe's?
     
  2. CWatters

    CWatters Guest


    A good electronics engineer will design his circuit to tollerate worse case
    parts. The spec says hfe can be as low as 40 or 30 and yours are higher than
    that so you should be ok.
     
  3. CWatters

    CWatters Guest

    I forgot.... sometimes it is necessary to use parts with a specific minimum
    hfe. Normally in such cases the designer will specify you need the C version
    of a transistor. For example they will specify you need a BC109C rather than
    just a BC109....however this is very bad practice. It's much better to
    design out the need for a specific hfe.
     
  4. So you are saying that all your transistors are within datasheet
    limits.

    hfe is not a very well controlled parameter (typically varying over a
    3 to 1 range in production). You had better learn how to design
    circuits to handle this range of variation or trim every circuit by
    hand.
     
  5. Sofie

    Sofie Guest

    Johan Wagoner:
    Your actual test results of the transistors were well within the
    manufacturer's specified range that you posted.
    If you need matched pairs for push-pull or parallel circuitry considerations
    then you can use selected transistors based on the results of your tests,
    otherwise they all meet specifications.
     
  6. John Larkin

    John Larkin Guest

    They're in spec.
    Depends on what you need.
    Decent circuit designs are beta-variation-tolerant. Fixed base current
    linear design is called "suicide bias"... some transistors may work,
    and some may not. Design to work over the transistor's spec'd beta
    range, or worse.

    John
     

  7. This is for use in the leach amplifier.
     
  8. Jason D.

    Jason D. Guest

    I never heard of CDIL, but that markings usually screams "GENERIC"!
    Didn't you got them for good price? If so that's the reason and and
    are faked.

    I got few stuff made by NSC and few of them looked real and had
    correct brands too marked and I don't trust them either because of too
    good to be true prices.

    In audio stuff, close hfe values usually is preferred to get smaller
    0V crossing distortations.

    The large transistors made for high power audio stuff are in 20 to 40
    dollars range not 5 bux range that generics abounds.

    Cheers,

    Wizard
     
  9. Al

    Al Guest

    Hfes from one transistor lot should be close. Variations are to be
    expected between lots. That's why the range in the spec is so high. If
    you want them close, you will pay extra for it. And most likely the mfgr
    will just select them for you.

    As an example, years ago, we tested a large lot of resistors of one
    value we had purchased. The purchase tolerance was +-5%. Yes, They were
    all in that range. But...there was a big hole in the plot at +- 1%. It
    looks like the mfgr had separated out all the resistors that were +- 1%
    from the lot and sold them as such. We got he +- 5%, which is what we
    had asked for. We were too stupid to specify a normal distribution in
    the resistor values.

    The same will hold for almost any component you buy.

    Al
     
  10. John Larkin

    John Larkin Guest

    Oh, audio. In that case, all rational design considerations are void.
    File the corners off the packages or dip them in red wine or whatever
    makes it sound best.

    John
     
  11. Jim Thompson

    Jim Thompson Guest

    ROTFLMAO!

    ...Jim Thompson
     

  12. Yous guys should start circulating a claim among the audiophiles that
    only amps and other audio electronics sound excellent if they were
    designed and drafted with pencil and drafting board. Any audio
    component won't have the right sound if it was designed with a lowly
    computter program!
     
  13. Jim Thompson

    Jim Thompson Guest

    What do you mean start circulating a "claim", it's TRUE ;-)

    ...Jim Thompson
     
  14. John Larkin

    John Larkin Guest

    The best audio interconnects are gold-plated, custom-bent hardline
    coaxial cables with SMA connectors.

    John
     
  15. Jim Thompson

    Jim Thompson Guest

    On Tue, 11 May 2004 08:04:08 -0700, John Larkin

    [snip]
    Not necessarily so!

    I had a fellow working for me that bought a Heapshit Preamp Kit many
    years ago.

    He didn't like the looks of the audio coax included with the kit, so
    he substituted some nice ultra-small diameter teflon cable (shielded)
    that we had in the lab.

    Bye, bye, high frequency response.

    ...Jim Thompson
     
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