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Cooking transistors: any recommendations?

Discussion in 'Electronic Design' started by Paul Burridge, Nov 20, 2005.

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  1. With "cooking" as an adjective rather than a verb!
    I'm just looking for recommendations as to a general purpose 'cooking'
    transistor that's a sufficiently good compromise to be able to
    reasonably handle both switching and linear amplification with low-ish
    noise. The kind of discrete device you can buy dirt cheap by the
    bucket-load. Power handling and transition frequency not critical;
    just a bonus.
    Anyone got any favourites they'd care to name?

    p.
     
  2. Tim Shoppa

    Tim Shoppa Guest

    Around here the preferred term seems to be "jellybean". You buy
    them in quantity, toss them off wherever you need them.
    2N4401 for medium-voltage low-current NPN bipolar applications. 2N4403
    is PNP counterpart. The plastic 2N2222/2N3904/2N3906 are similar but
    not quite as good for most purposes.

    MPSA42 for voltages up to low hundred V in NPN. MPSA92 for PNP.

    ULN2003/2803 when you need 7 or 8 NPN common-emitter switches in a
    single package.

    Above currents of a few hundred mA or powers above a fractional watt,
    things aren't so jellybeanish. TIP30/TIP31/2N3055 are common choices
    and readily available but really are far from the cream of the crop
    compared to better and likely cheaper choices for individual
    applications.
    Non-bipolar transistors are often superior choices, the 2N7000 for
    example. Even though everyone will tell you it's a switch,
    I've seen it used in some surprising linear applications!

    Tim.
     
  3. Low level, low noise, high gain less than 50 mA collector current):
    NPN 2N5089
    http://www.onsemi.com/pub/Collateral/2N5088-D.PDF
    PNP 2N5087
    http://www.onsemi.com/pub/Collateral/2N5087-D.PDF

    General purpose, less than 300mA collector current:
    NPN 2N4401
    http://www.onsemi.com/pub/Collateral/2N4401-D.PDF
    PNP 2N4403
    http://www.onsemi.com/pub/Collateral/2N4403-D.PDF

    You will never run out of things you can build with these 4.
     
  4. Guest

    A somewhat indirect answer to your question would be that when
    designing its good practice to specify more than one device that can be
    used. This is usually easy with ubiquitous little trannies, rather less
    so with power devices.

    Designing for several possibles makes sourcing much easier, and reduces
    stock range, which all helps reduce costs. Its especially useful when
    designing for a company in another country.

    It isnt always appropriate of course.


    NT
     
  5. Among the ZTX000 series are some pretty good workhorses suitable for
    around 1 to 2 amps and up to over 100v - but they aren't the rock-bottom
    cheapest.
     
  6. John  Larkin

    John Larkin Guest

    I like BCX70/71. Betas are huge.

    And 2N7002 whan a fet is appropriate, which is most of the time.

    John
     
  7. Tim Wescott

    Tim Wescott Guest

    I've had a couple of bottles of TO-92 case transistors for 20 years now;
    I'm slowly working through them. They're from a big box of stuff
    donated by Tektronix to the Portland State IEEE student chapter. We
    just loaded up a pound (or maybe 5) of stuff per box and sold them for a
    couple of bucks per box.

    They're all house-marked, but whenever I need a jellybean small signal
    transistor I just shake one out and use it. Hasn't gone wrong yet.
     
  8. Tim Williams

    Tim Williams Guest

    Well I don't care! I personally like them smoked over an open fire...

    Tim
     
  9. Barry Lennox

    Barry Lennox Guest


    "Cooking" should be anything you can get cheap or surplus: Personally
    I have scored, free, or almost for free, large qtys of:

    ZTX xxx (Several p/ns)
    2N2369A
    2N3055 both metal and plastic
    and several others whose specs are almost irrelevant, I just got
    hundreds for free.

    They all work fine,

    Barry Lennox
     
  10. Tim Wescott wrote...
    That's the term we tend to use, instead of cooking.
     
  11. John  Larkin

    John Larkin Guest


    Maybe back East you do. Out West we call them gumdrops.

    John
     
  12. Tam/WB2TT

    Tam/WB2TT Guest


    2N2369 for NPN
    2N5771 for PNP

    Tam
     
  13. Aren't 2n2369s gold doped? (It has been a long time since I played
    with those.) IF they are gold doped, they might not be optimal
    for small signal applications (they might be a little more noisy.)
    Perhaps it was the 2n706 that were gold doped? I seem to remember that
    the 2n706 tended to be noisy as HF/VHF oscillators. AFAIR, the gold
    doping helped to mitigate some of the storage effects of saturation.

    2n2369s are moderately fast (given transistors of that era), and I
    seem to remember that the batch that I had many years ago had the cool
    negative resistance effect (leave base open, relaxation oscillator
    with neg resistance between collector/emitter. I seem to remember that
    it required 20-30V of bias. The transistor would no longer work very
    well as a regular transistor after abusing it as a negative resistance
    oscillator, but YMMV.) These memories come from the 1970-1975 timeframe,
    so might be a little distorted.

    Nowadays, for non-switching applications, perhaps an MPSH10 might
    be a slightly better choice for the NPN.

    John
     
  14. qrk

    qrk Guest

    I thought out west was "plain vanilla".
     
  15. Rich Grise

    Rich Grise Guest

    Is a "cooking" transistor a transistor that you cook with? ;-)

    But speaking of grab-bags, I once had a job as a Radio Shack floordroid.
    I saw them make up a grab-bag once, and it was composed of trash from
    behind the counter (like, returns, or stuff that they didn't buy but
    nobody had got around to re-shelving) and, yes, literally, stuff we found
    on the floor.

    Cheers!
    Rich
     
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