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Isolating 2 ckts from same pwr supply

Discussion in 'Electronic Design' started by Elephant, Apr 10, 2004.

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  1. Elephant

    Elephant Guest

    I want to use one 9vdc power supply to power two individual
    circuits, but I want to isolate the two. In other words, the
    two circuits have to act as though they are being powered from
    seperate supplies, like two 9v batteries.

    Can a diode arrangement be used for this?
     
  2. I read in sci.electronics.design that Elephant <>
    Probably not. It depends on the exact circuit arrangements, why you
    want/need to keep them 'isolated', and even what you mean by that.

    If their ground/earth/zero volts lines can't be connected together, the
    problem is almost certainly insoluble.
     
  3. Joerg

    Joerg Guest

    With an isolating DC-DC converter this could probably be done.
    Watch out for noise and other issues though.

    Regards, Joerg.
     
  4. Ken Smith

    Ken Smith Guest

    Exception:

    Circuits like this can also be built:


    9V --------------- To 9V CKT
    !
    !
    /c
    Va ---! NPN
    \e
    ---------- To + side of other circuit
    ---------- To - side of other circuit
    /e
    Vb ----! PNP
    \c
    !
    0V -------------------- To 9V CKT


    The Va and Vb could come from a circuit that always keeps a 3.3V plus 2
    diode drops between them but has them slide up and down in some way with
    respect to the 9V.
     
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