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BC337 hfe distribution

Discussion in 'Electronic Design' started by E, Apr 9, 2010.

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  1. E

    E Guest

    Just measured hfe from some BC337-40 at about 5 mA collector current.
    Unfortunately nothing very interesting there

    Sample size: 960 pcs
    minimum hfe: 388
    maximum hfe 513
    (datasheet limits are 250 and 630)
    avarage: 452
    avarage deviation: 27
    median: 463
    mode: 477
    Distribution is a bit strange looking with two spikes
    Histogram here:

  2. E

    E Guest

    Possibly, alltought they were all from same bag.
    Or maybe just from different wafers?
    How many BC337 fit one wafer? Probably quite many...

  3. Perhaps they take all the middle ones for a tighter-spec version?
  4. E

    E Guest

    They have still not managed to get their processes so much under control
    that they can
    make what is needed instead of what happens to come out? BC337, BC547,
    2N2222 etc. have been
    around for quite some time... (Google didn't know how long)

  5. Sjouke Burry

    Sjouke Burry Guest

    That looks awfully like a mix of two production runs......
  6. Tim Williams

    Tim Williams Guest

    First hit for "2N2222 history", a few pages in:

    Introduced by Motorola in 1962.

    Anyone know how much it retailed for that year?

    With the loose specs on a 2N2222, you'd think a fairly loose run could be
    binned into all sorts of parts. Maybe they did, once upon a time. 'Course,
    the 2N2222 spec (and the other three in the series) is so loose as to avoid
    that, at least initially.

    I've heard at least one suggestion that modern 2N2222s should be avoided
    because, due to the lax specifications, modern processes could be
    dangerously faster than the original, leading to parasitic oscillation where
    you aren't expecting it.

    Personally, I use 2N3904 and 2N4401, which have proper spec sheets.

  7. Hammy

    Hammy Guest

    I wouldnt waste your time. Transistors will be obsolete according to
    HP. ;-)

    I never heard of this (memristors)?

    "Hewlett-Packard scientists on Thursday are to report advances in the
    design of a new class of diminutive switches capable of replacing
    transistors as computer chips shrink closer to the atomic scale. "

    "The most advanced transistor technology today is based on minimum
    feature sizes of 30 to 40 nanometers — by contrast a biological virus
    is typically about 100 nanometers — and Dr. Williams said that H.P.
    now has working 3-nanometer memristors that can switch on and off in
    about a nanosecond, or a billionth of a second. "
  8. Tim Williams

    Tim Williams Guest

    Wow, that's slow. I have 2N3904s that avalanche faster than that!

    'Course, they're referring to the memristance effect, which is fundamentally
    different. When it comes to moving ions in a crystal, that's not too bad.

    Heh...speaking of moving ions... wouldn't the gate threshold voltage
    hysteresis of sodium impurities have a similar effect? But since it's on a
    gate, it would be more of a transmemristance effect? :) I wonder if a
    couple sodium ions buried into a regular DRAM cell could have any useful
    effect. (Note it's probably a good idea to deposit sodium only in the
    active cells, and not the word line switches...)

  9. In Europe, traditionally a letter is appended at the end of the type
    designator to signify the current gain group. If you specify just
    "BC337", it is quite possible that transistors belonging to a specific
    group may have been taken out.

    In a similar way, if you order 5 or 10 % resistors/capacitors, there
    might be deep dips in the distribution close to the nominal E12/E24
    values, as these are selected out and sold as 1 % components.
  10. Hello ek,

    Have you measured half of the transistors on the other day when the
    room temperature was a few degrees different?
    Current gain of transistors heavily depends on temperature.

    Best regards,
  11. E

    E Guest

    No, they are all measured within three hours.
    I just looked at the data file in 250 pcs slices and
    distribution looks about same in each slice.

  12. legg

    legg Guest

    BC337-40 is a binned-by-hfe part number, so you can't expext a
    'natural' hfe distribution curve.

    For such a natural distribution, you'd need a part number not subject
    to selectuive processing, 'probably' made by a firm that does not
    offer that service for any of it's produce.


  13. E

    E Guest

    Yes, it is hfe binned part. Unfortunately I don't have many non-hfe
    binned transistors, but found some MPSA42 high voltage bipolars.
    hfe distribution is actually pretty similar in those than in bc337.
    Min-max:118-142, relative avarage deviation: 2.6%

    Maybe I need to buy some more of them to get some idea about
    batch-to-batch variation
  14. I can only speak for NXP, but it's more like 200k on a 6" wafer (I can
    look up the actual number).
    Not quite. They auto-bin whole wafers into different selection groups of
    the same type. Meaning that entire wafers end up in one group.
    Absolutely. More than 10pcs/sec eutectic die bonding and wire bonding,
    and a whole assembly line still many hours for a single BAV99 wafer.

  15. Yes they have.
    They do. Maybe it hasn't been always that way, but nowadays when a batch
    starts into the line as BC547 it'll come out as 547.

  16. legg

    legg Guest

    For applications requiring gain spreads that are narrower than those
    offered by the vendor, you already seem well situated to address the
    issue, by direct measurement.

    Before accepting hfe as a critical design parameter, you'd best
    examine effects on measurement method-induced and general
    environmental effects on this feature, reversible or otherwise.

    This information may be more economically obtained from a good
    reference library, or even a simple google search......

  17. Also don't forget that certain parameters may shift over the lifetime of
    the part while staying in spec. An extremely unwanted property of
    electronic devices but sometimes hard to get rid of.

  18. Fred Bartoli

    Fred Bartoli Guest

    whit3rd a écrit :
    Hfe with aging? What's the mechanism?

    Same Q...

    Google didn't help...
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