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[email protected] down to [email protected]

Discussion in 'Electronic Basics' started by Brian, Dec 31, 2003.

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  1. Brian

    Brian Guest


    The simplest solution would be to use a LM338K regulator. If you want to
    use the LM7812, you would need to use a power transistor to boost the
    current, up to the 4.5 amps that you want. To do that, I drew up the
    schematic for you. You can see it at

    If you would like to go the switching regulator route, I could draw up
    the schematic for that too. Let me know.

  2. I have a DC supply that says [email protected] out...

    I have a DC Device that wants [email protected] in....

    I know ( think ) that I can use a LM7812 to step down
    the volts from 16 to 12... but the LM7812 is only rated
    to 1Amp.

    Also... a LM7812 says that the output varies from 11.5 - 12.5
    (min 11.5, typical 12.0, max 12.5 ). I want 12.0 +- 0.2 ...
    not 12.0 +- 0.5.

    How is this normally handled?

    Thanks - jack
  3. A better regulator? ;-) Seriously, 4V @ 4.5A is 18W, which is quite a
    bit of heat to dissipate, but not an impossible task. I'd look around
    for a buck regulator design to try to reduce the waste heat. Buck
    regulators will be more complicated than a linear, but will simplify
    your cooling.

    National ( has some pretty good application
    notes on line. I've "stolen" buck regulator designs from their app
    notes a time or two. ;-)
  4. Garrett Mace

    Garrett Mace Guest

    National ( has some pretty good application

    Hmmm, I think "adapted" works well as a word choice in those situations.
  5. Nahhh !! I like the brutal honesty :)
    (So refreshing in todays values)
  6. The unvarnished truth is that I'm not paid to produce a result,
    not to invent. Well, I am paid to invent, but certainly not to
    (re)invent buck regulators. I'm not above stealing other's
    designs (patent issues excepted) to get my work done. Though I
    am nice enough to buy their parts. ;-)
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