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How would one use NPN transistors only?

Discussion in 'Electronic Design' started by B, Jun 8, 2004.

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  1. Terry Given

    Terry Given Guest

    perhaps pnps with gold-plated leads provide a "purer" sound, especially if
    hand assembled by one-legged lesbian dwarves :)

    cheers
    Terry
     
  2. Ken Smith

    Ken Smith Guest


    NPN : make Vcc +
    PNP : make Vcc -

    Either way it works.
     
  3. Or read the three recent (long) threads here (and in

    alt.binaries.schematics.electronic):
    Trouble shooting Push-Pull amp
    Distortion from audio power amp
    Are these 2N3055s borderline spec?

    which include various examples.
     
  4. On a sunny day (Wed, 9 Jun 2004 02:54:36 +0000 (UTC)) it happened
    Yep, and you even added that nice boost cap from the output!
    JP
     
  5. **** Post for FREE via your newsreader at post.usenet.com ****

    On a sunny day (Wed, 9 Jun 2004 02:54:36 +0000 (UTC)) it happened
    Yep, and you even added that nice boost cap from the output!
    JP
    Sorry if this shows up twice, the usenet server teranews seems not working, posting via
    post.usenet.com.
    JP

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  6. Ken Smith

    Ken Smith Guest

    The performance is really bad without the bootstrap.
     
  7. Jim Thompson

    Jim Thompson Guest

    I will post the MC1554 amplifier to my website in a few minutes.

    I won a coffee bet with Tom Frederiksen back in the mid 60's over this
    scheme, proving I could make a power output stage with just NPNs.

    ...Jim Thompson
     
  8. Jim Thompson

    Jim Thompson Guest

    See "MC1554-AudioPowerAmp.pdf" on the S.E.D/Schematics Page of my
    website.

    ...Jim Thompson
     
  9. Fred Bartoli

    Fred Bartoli Guest

    LOL !!!

    Thanks,
    Fred.
     
  10. Jim Thompson

    Jim Thompson Guest

    See my other posts.
    There is NO advantage except *perhaps* cost. PNP-NPN combos to
    emulate a power PNP are potentially unstable and are difficult to
    match loop gain for positive and negative swing directions.

    ...Jim Thompson
     
  11. Rick

    Rick Guest


    Don't see how this can work - the output stage's darlington has its
    base and emitter clamped to almost the same voltage by the two
    diodes connected to pin 8; it won't conduct.
     
  12. Jim Thompson

    Jim Thompson Guest

    LOL! Do some more thinking before "shooting from hip" ;-)

    ...Jim Thompson
     
  13. Fred Bloggs

    Fred Bloggs Guest

    Well- that's the point- the pull-up Darlington is cut-off by the
    conduction of the pull-down Darlington...the idea , for the output at
    least, is borrowed from the earlier totem-pole output drive
    architecture. The diode with anode to pull-up Darlington base is a
    virtual reflection of the output node voltage to the base-node, ensuring
    0V combined 2x Vbe drop, and therefore cut-off, whenever the diode at
    pull-down Darlington collector conducts.
     
  14. John Larkin

    John Larkin Guest

    I sure Jim will be dismayed to discover that hundreds of thousands of
    these chips were manufactured, and none of them ever worked!

    John


    ps - two questions:

    1) was this the first ocurrence of...


    +----+---v+
    | |
    r |
    | c
    +---b
    | e
    | |
    +-ka-+-----out
    |
    |
    c
    in--b
    e
    |
    gnd


    2) Did Jim Thompson invent crossover distortion?
     
  15. Jim Thompson

    Jim Thompson Guest

    I don't know.

    My extra diode cuts the deadband to a single vbe when a Darlington is
    used.

    I've used your representation to make TTL outputs from split supply
    comparators with an extra diode to clamp the output to a "low" of
    ground, as marked-up above. Note the R added in series with the
    bottom collector....

    +----+---o v+
    | |
    r |
    | c
    +---b
    | e
    | |
    gnd-ak-+-ka-+----o out
    |
    R
    |
    c
    in o--b
    e
    |
    +---o v-
    No, but I've certainly created a lot ;-)

    ...Jim Thompson
     
  16. Rick

    Rick Guest

    Thanks, Fred. Got it.
     
  17. John Larkin

    John Larkin Guest

    We recently did a "pin driver" a lot like that, with surfmount
    gaasfets instead of bipolars. Bottom transistor is a switched
    constant-current gaasfet cascode. It works really good, 15 volt
    programmable Vh/Vl swing and screaming fast, but it's a power hog.
    Somebody needs to make a good IC pin/output driver.

    John
     
  18. Jim Thompson

    Jim Thompson Guest

    MANY years ago I designed programmable pin-driver chips for GenRad.

    ...Jim Thompson
     
  19. J M Noeding

    J M Noeding Guest

    In the early 60's PNP devices were more readily available and lower
    cost than NPN devices, it was not difficult to build all sorts of
    amplfiers, so it is just the other way around using NPN

    Would have been nice trying PNP-type tubes.....
     
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