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I want a transistor

Discussion in 'Electronic Design' started by Tim Williams, Nov 19, 2007.

  1. Tim Williams

    Tim Williams Guest

    In the search for a fast, high voltage transistor, I've found the perfect
    type: 2SC4679. Problem: it only exists in datasheets. The usual suspects
    don't sell it or its equivalents.
     
  2. Joerg

    Joerg Guest

    You didn't mention: How fast? How high in voltage? Since Toshiba doesn't
    seem to find it that transistor may be gone. HV plus fast usually means
    video transistor, the ones that drive the CRT. But since CRTs are going
    the path of the dinosaurs now ...
     
  3. John Larkin

    John Larkin Guest

    Fast? High voltage? Could you please be a little less specific?

    John
     
  4. How many volts do you need?
     
  5. That is a nice one, 300V, 100mA, 240MHz, 3pF, 8W. Nice.
     
  6. BobW

    BobW Guest

    Entering the p/n into Google gave this:

    http://www.planetonecomponents.com/part/2SC4679.phtml

    They claim to have 1233 of them.

    Bob
     
  7. Boris Mohar

    Boris Mohar Guest

    Enter the part number in Mouser and you get a relay :) LOL

    http://www.mouser.com/search/refine.aspx?Ntt=2SC4679
     
  8. John Fields

    John Fields Guest

  9. DaveM

    DaveM Guest

    Aye, Captain! And a very FAST relay it is, too!!!

    --
    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
    address)

    "In theory, there isn't any difference between theory and practice. In
    practice, there is." - Yogi Berra
     
  10. Tim Williams

    Tim Williams Guest

    250 million switch closures per second! Wow! But it's only rated for four
    seconds continuous use! :'(

    Or something like that...

    Tim
     
  11. Tim Williams

    Tim Williams Guest

  12. Tim Williams

    Tim Williams Guest

    Refs I saw for it state something like HDTV chroma/video output, so it
    can't be *too* dead.

    The Toshiba datasheet I found for it is dated 2001. How often do they
    rotate their parts numbers?

    Why is it that, for all the billions of transistor types made by a hundred
    countries around the world, 3 x 10^5 are 30V, 100mA NPN general
    purpose/switching transistors, and about four are the type I actually want
    at any given moment?

    Tim
     
  13. BobW

    BobW Guest

    You need to start thinking outside-the-box, Tim. Sell the other 9,998 on
    Ebay.

    You're welcome, in advance.

    Bob
     
  14. Joerg

    Joerg Guest

    Well, one of the last HDTV series is the Samsung SlimFit 30". A very
    nice set. I almost fell for it but it's a tad too small and very heavy
    so even I as a rather conservative shopper will probably head out this
    week and buy a Vizio 37" at Costco. So there you go, the market for
    those transistors just shrank by another three devices.

    I don't think they rotate. It's just that markets vanish. 20 years ago
    you could buy CRT driver transistors at almost any electronics place and
    TV repair shops. No more.

    Tell me about it. I guess we are in the same boat, just in other market
    segments. I was especially sad when FET arrays such as the SD5400 began
    their trek to lalaland.
     
  15. Fred Bartoli

    Fred Bartoli Guest

    Winfield Hill a écrit :
    Yup.
    And I recently found some interesting compementary pairs that might be
    useful:

    Toshiba:
    2SC5171 180V, 2A, 20W, 16pF, 200MHz
    2SA1930 180V, 2A, 20W, 26pF, 200MHz

    Want really fast?
    Try those Philips/NXP
    BFQ232,232A NPN 100V/115V, 300mA, 1.4GHz, 2pF, 3W-TO126
    BFQ252,252A PNP 100V/115V, 300mA, 1.3GHz, 2.5pF, 3W-TO126
     
  16. Eeyore

    Eeyore Guest

    Actually he didn't.

    Graham
     
  17. Eeyore

    Eeyore Guest

    How can they require you order 10,000 if they only have 1,233 ? You're being
    silly. Posts in sci.electronics.components suggest the brokers will indeed
    supply small quantities albeit at higher prices than you might want.

    So what do you want this device for ? The application makes all the difference.


    Graham
     
  18. Tim Williams

    Tim Williams Guest

    Whoa, 2A? Is that peak (low average dissipation, possibly TO-92 -- emitter
    follower stock) or continuous? I'm not interested in burning more than
    100mA quiescent here...
    Ayup, I have a few like that -- BFQ225 is 100V, ~1GHz, 100mA, TO-202
    package. The monitor boards came with a PH2369 at the bottom of the
    cascode and a complementary pair of BFQ221/241 emitter followering into the
    CRT grid. :)

    Not enough voltage though.

    Tim
     
  19. Tim Williams

    Tim Williams Guest

    Approximately what they're designed for. If you recall a past conversation
    of mine here, you might realize I'm interested in making a fast,
    high-voltage, balanced amplifier:
    http://webpages.charter.net/dawill/tmoranwms/Elec_Scope1.html

    2SC1569's topping out at about 5MHz:
    http://webpages.charter.net/dawill/Images/20MHz_Amp1.jpg
    I have yet to try cascode perzactly but having increased drive current to
    levels comparable to bias current, it's not looking good.
    http://webpages.charter.net/dawill/Images/20MHz_Amp.gif
    Changed C1569 emitter resistors to 47, supply to +150V, 2N3904 emitter
    resistors (to -9V) to 150 ==> around 80mA bias floating around the output
    bases. Even with emitter capacitor (actually 330pF, not 220 shown) and
    peaking inductors, rise time tops out at 100ns (or was it 50) and F3 circa
    5MHz.

    Tim
     
  20. John Fields

    John Fields Guest

     
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