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Transistor as a current limiter

Discussion in 'Electronic Basics' started by Lauri Alanko, Jul 5, 2013.

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  1. Jasen Betts

    Jasen Betts Guest

    all NPN emitter marked 'e'

    I_set I_LED
    V V
    | |
    +-----. |
    \ | /
    \| | |/
    |--+----------|-----...
    /| |\
    e e
    + +
    | |
    / \
    \ 22R / 22R
    / \
    | |
    Q1 / /
    +V |/ enable |/
    --[1K]-| ---[1K]--|
    |\ |\
    e e
    | |
    --+-------------------+---...

    scale the 22R as apropriate for your application 200mV drop is plenty
    scale the 1K sufficient to ensure reasonabe saturation.

    Q1 can probably be replaced by the apropriate resistor
    (measure or calculate)
     
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