Connect with us

triple darlington?

Discussion in 'Electronic Basics' started by Kevin Aylward, Jul 22, 2004.

Scroll to continue with content
  1. Its called, now get this, "a Triple"

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
  2. andy

    andy Guest

    is there any reason you can't make a triple darlington transistor, with
    Hfe=Hfe^3 by adding a third transistor to a darlington pair in the same
    configuration?
     
  3. andy

    andy Guest

    ok, thanks.
     
  4. CFoley1064

    CFoley1064 Guest

    Subject: triple darlington?
    Hi, Andy. I would guess you mean something like this (view in fixed font or M$
    Notepad):

    "Triple"
    C
    o
    |
    .---o---o
    | | |
    |/ | |
    Bo-| Q1 | |
    |> | |
    | |/ |
    o-| Q2 |
    |> |
    | |/
    o-| Q3
    |>
    |
    o
    E

    created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

    First you need to understand that all transistors have some leakage current
    when they're "off". With the combined beta of the "triple", the low microamp
    or high nanoamp leakage of Q1 will be amplified by Q2, and then be enough to
    turn on Q3. So, even if you have no current whatsoever going into the base,
    significant current will be flowing from the collector to the emitter. Not
    only that, but the leakage current is temperature dependent, so your triple
    transistor characteristics would change dramatically once it was powered up.

    Darlington transistors are great for switching things on and off, and they do
    have their uses, but there's reasons you don't see them everywhere. Keep
    learning about transistors, you'll see why.

    Hfe of a regular darlington is usually well over 1,000, anyway. That should be
    enough. But it is a good question. I remember asking this myself back when I
    was learning this stuff (midway through the Pleistocene Era, as I remember)

    Good luck, and keep learning
    Chris
     
  5. andy

    andy Guest

    just tried this out under linux using 'wine' - neat program.
    thanks - that was the sort of thing i wanted to know - i.e. how long can
    you keep adding transistors b4 it gets ridiculous.
     
  6. Note that practical Darlington's and triples usually have base emmiter
    resisters to reduce leakage and speed up turn off.

    Kevin Aylward

    http://www.anasoft.co.uk
    SuperSpice, a very affordable Mixed-Mode
    Windows Simulator with Schematic Capture,
    Waveform Display, FFT's and Filter Design.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-