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really low power transistors

Discussion in 'Electronic Basics' started by [email protected], Dec 19, 2008.

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  1. Guest

    Anyone recommend any NPN transistors with around 0.1-0.3VBE sat. ?

    I did a mouser search but apparently Vbe sat. isn't a commonly
    specified parameter... ?


  2. ian field

    ian field Guest

    Either the OP has got the terms mixed up or wants a germanium transistor.
  3. Guest

    Yeah, low power isn't necessarily equal to low Vbe_sat, but I figured
    a 0.1Vbe_sat transistor wouldn't be an output transistor in a 100W
    audio amplifier anyway...


  4. ....

    What a coincidence - I just subscribed here to ask that exact question.
    Well, my question's a little more complicated, so I'll do another
    thread for it.

    As to your question - I found low Vcesat ... oh, wait - you wanted low
    V_be_sat. Or did you? Anyhow, ON Semi has SMT BJT's down to 50 mv Vcesat:

  5. Phil Allison

    Phil Allison Guest

    "John Larkin"

    ** You didn't read the question.

    The trolling fool wants Vbe sat to be impossibly low.

    .... Phil
  6. Jamie

    Jamie Guest

    When I don't have that info in front of me, I usually go for a
    low Vceo range, the Vsat is normally lower.

    Your search is average for a unit in the 20 Vceo range."
  7. Eeyore

    Eeyore Guest

    Vbe ?

    Do you mean Vce ? Shouldn't be a problem. 2N4401 2N4403 are very low
    IIRC. Mind you @ what current ? You're really not supplying enough info.

  8. Eeyore

    Eeyore Guest

    You're talking nonsense.

  9. Eeyore

    Eeyore Guest

    Yup 50mV is no trouble.

  10. Hammy

    Hammy Guest

    Yes Zetex has about the best low VCE sat BJT's that I've found. The
    FMMT491 and FMMT618 to name two.

    Onsemis got a couple too the NSS40201LT1G and the NSS40301MZ4 they're
    a little pricey though.
  11. Guest

    Yes, that.

    No, not that.


    Mr. Larkin had an interesting idea. If I wanted to say power a boost
    converter (0.1 V to 1V) could I just feed the 0.1V to the base of my,
    eh, 2N3904 NPN and it would work (at just incredibly low efficiency,
    since it's not in saturation)?


  12. Guest


    Shouldn't be a problem. 2N4401 2N4403 are very low

    @ < 100 mA. Not expecting much @ 0.1V.

    Actually the 0.1V was kind of optimistic, come to think of it...

  13. krw

    krw Guest

    Vbe with collector open?
  14. Guest

    Funny. I would have thought they are common. Guess I was wrong.

    Anyhow... I was thinking of making some sort of super-tiny electric
    generator (basically just a magnet loosely moving inside a coil of
    wire), and boosting that up to, oh, 1 volt or so, to light up an LED.
    Another challenge would be to rectify the tiny current... guess I
    can't use normal diodes (0.7V drop... oh well...)

  15. ehsjr

    ehsjr Guest

    No, it wouldn't work at all, unless what you have in
    mind is different than what you seem to be saying.
    Give us a schematic of what you are thinking about.

  16. Guest

    Homemade shake-generator (plastic can, coils of wire outside, magnet
    inside), bridge rectifier (Schottky?), capacitor, boost converter, LED

  17. Sjouke Burry

    Sjouke Burry Guest

    I have done what you intended, removing the magnet/coil
    assembly from broken harddisks, and attaching 2 leds
    antiparallel to the coil ends.
    No need for rectifying, or boosting, just wiggle the coil
    were it used to be, and the leds will light just fine.
    Also interesting is, to shortcircuit the coil, and try to move
    it, it acts as if inserted in syrup.
    If you want more voltage from it use a small transformer.
    using the primary as output, you get all the voltage you want.
  18. Jasen Betts

    Jasen Betts Guest

    get a stronger magnet, and/or use more turns in the coil.
  19. Eeyore

    Eeyore Guest

    Well you can't do that with silicon (look at Vbe vs Ic)and you may have some
    trouble finding germanium devices.

  20. Eeyore

    Eeyore Guest

    Read up on device physics !

    Put more turns on the coil. Easy. And use Schottky diodes.

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