Easiest way to increase current supply from a linear voltage regulator?

Discussion in 'General Electronics Chat' started by Subterranean, Jan 15, 2011.

  1. Subterranean

    Thread Starter New Member

    Jul 27, 2010
    I'd like to take a voltage from a normal linear voltage regulator, a 7812 for instance but I may end up pulling a bit more current than the 1A it's rated for. I've been looking for easy ways to increase this and I found the following page:
    I am especially looking at the colour images in the comments section at the bottom. They show a positive regulator (78xx) paired with a NPN transistor (with some caps and resistor). Would this work? Everything else I've read says a positive regulator must be paired with a PNP transistor and visa versa for negative regulators (like in the very first image on that page, not in the comments section).

    If the circuits in the comments section wont work, is the first circuit on the page taken from the datasheet of the regulator the best way to increase current supply?

    Thanks for any help.
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    The 78xx driving transistor(s) for higher current is a simple method of increasing current, but it is very inefficient. Using 6 transistors off a 7812 for reference voltage would dissipate 100% of the voltage difference between input and output as heat.

    What are your input voltage, output voltage, and current requirements?

    A Switch Mode regulator may be closer to what you are trying to get, though they are a bit more complicated, they are a lot more efficient.
  3. timrobbins

    Active Member

    Aug 29, 2009
    If "I may end up pulling a bit more current than the 1A it's rated for" is say less than say 2A, then consider using 2 or 3 regs in parallel. Regs are cheap, and circuit change is dead simple. Heatsinking loss goes up. They don't share at low current levels (use a series output resistance for each reg - regulation not as spot on), but they do share ok at higher current levels (if both on same heatsink). Of course it is assumed your power source is up the increased rating.