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Strange high frequency push pull transformer action

Discussion in 'Electronic Design' started by mook johnson, Nov 4, 2012.

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  1. Guest

    You're about as stupid as they come,UsuallyWrong.
     
  2. Joerg

    Joerg Guest

    It never completely unloads, there will always be capacitances in the
    transformer and in the FET.
     
  3. Fred Abse

    Fred Abse Guest

    I like that!
     
  4. ehsjr

    ehsjr Guest

    I thought that was how you prepped them for playing the blues. :)

    Ed
     
  5. Bill Sloman

    Bill Sloman Guest

    John Fields isn't spectacularly clever, but he's nowhere near as dumb
    as krw, and he's certainly not AlwaysWrong, as anybody only a trifle
    brighter than krw would be aware.

    The name AlwaysWrong has been attached to somebody who posts under a
    variety of pseudonyms, and "John Fields' isn't any of them.
     
  6. Bill Sloman

    Bill Sloman Guest

    There's certainly that kind of stuff in the literature. I don't know
    how tightly they've coupled lead in electronic solder to intellectual
    development difficulties in kids, but the connection to lead in the
    environment (and in the kids) is solid.
    You would. It's not a preference you'd want to advertise.
     
  7. Guest

    Good Lord, you're stupid! Read, why don't you? Then take a few
    minutes to understand. *I* don't ship products to Europe, though my
    company does - and manufactures there. *I* design and debug
    prototypes (platforms used for future products). RoHS doesn't mean
    shit to our lab. We use RoHS processes for boards because it's hard
    to find anyone who doesn't do RoHS anymore, even harder to find leaded
    parts, and we use the same parts that the eventual product will use,
    anyway. Got it, dummy?
     
  8. Guest

    I sure don't. ;-)
     
  9. Guest

    Naturally, but nothing with a time constant long enough to pass a 30nS
    square pulse.

    Fred had a good idea--test the transformer out-of-circuit.

    I'm looking forward to Mook telling us the solution to his puzzle.
     
  10. Tim Williams

    Tim Williams Guest

    So, no? Not even the electronics part specifically is really necessary,
    but the landfill part would be good to know. Most electronics goes into
    landfills (or is disposed of overseas) anyway, so it would be a
    straightforward link to draw between leaded electronics and landfills.
    Plus there's a lot of other rather nasty shit in those piles that would be
    unattractive at best to be drinking, beyond just lead.

    Now... that "overseas" part is interesting, because most 3rd world people
    just burn the shit to get at the copper, releasing all manner of awful
    chloro-bromo-fluoro-trans-cadaveroxyl-horribleinates which they aren't
    even wearing masks for, not that a mere dust mask would even help that
    much. Again, lead isn't as much of a hazard from inhalation, maybe the
    dust -- but the burn piles will retain a whole lot of it, and that's not
    very good for the people or the land. So give or take the disposal method
    (open or closed, overseas or recycled, etc.), it would be environmentally
    and morally responsible to use less toxic / more burnable/disposable
    materials, in general.
    When I signed the lease to this [old-ish, '50s era I believe] apartment, I
    had to sign a disclaimer acknowledging it contains leaded paint. It's
    definitely a good thing to be aware of. My neighbor has a little girl, be
    a shame if she started eating paint chips. Every so often I hear violin
    sounds from across the hall, which has the characteristic waver of an
    inexperienced player, but given she's probably 8 or so, I'd guess she's
    doing very well.

    Tim
     
  11. Joerg

    Joerg Guest


    But then he'd see an almost dead short on his +5V rail because the body
    diode shunts it to GND.
     
  12. Jamie

    Jamie Guest

    God, you're unbearable. You didn't move to Sydney by choice, I bet
    they deported you! Most likely couldn't afford any more brain dead
    geezers sucking on the funds.

    Jamie
     
  13. John S

    John S Guest

    Then why are you bearing him? Go away.
     
  14. Joerg

    Joerg Guest


    All FETs have body diodes, it is an intrinsic part of the respective
    semiconductor production process. The body diodes are, from a current
    carrying capability, similar to the FET itself except that you have to
    watch dissipation if you plan on using the body diode (I often do).
     
  15. All power MOSFETs (AFAIK) have body diodes, but I think mostly RF
    FETs* don't and certainly JFETs don't.

    Although free, the body diode is often a PITA since it has sluggish
    recovery and has high voltage drop so we often parallel it with a good
    diode, such as a Schottky. "FETKY" products combine the two in one
    package. The diode tends also to do bad things if power connections
    are reversed, often requiring some extra thought and/or protection.

    *Eg. BSS83, which has a separate substrate connection. Not sure about
    the dual-gate RF MOSFETs.. I think they do not as well.
     
  16. legg

    legg Guest

  17. Guest

  18. Joerg

    Joerg Guest

    Any MOSFET does. The 2N7002 that the OP used are MOSFETs.
     
  19. Joerg

    Joerg Guest

    A Schottky is a problem because it must be huge. One trick I sometimes
    use is to make sure the FET comes back on when the body diode wants to
    conduct but lets go when the current approaches zero. Can be a
    white-knuckle ride though, must be done with care. If someone built a
    very fast deive for that they could make lots of money. The usual ones
    are sluggish, one would need 10nsec, 20nsec max.

    The SD5400 has that as well. A marvelous chip because it's a monolothic
    array of four. And, unlike crude oil, its price has come back down to
    about where it was in the 90's,
     
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