7806 with NPN pass transistor?

Discussion in 'General Electronics Chat' started by santonel, Feb 28, 2010.

  1. santonel

    Thread Starter New Member

    Feb 28, 2010
    Hey everyone. I'm kind of new to electronics, just started a couple months ago but I'm enjoying it. Anyways I'm working on a circuit that needs a steady supply of 6v and when it's done I expect it to draw about 1.1A. I got a 7806 regulator which, according to the datasheet can supply about 1A when heatsinked (Or was that 1.5A?).

    I'd like to be on the safe side and not run it over spec. The datasheet says you can build a circuit with a pass transistor to allow more current but the type you need is PNP. I don't have any pnp transistors but I do have a bunch of NPN power transistors (and a couple N-type Mosfets). Is there a way of building an equivalent circuit with an npn transistor? There's not much in the way of electronics stores here so I'd have to order a pnp transistor online and Id rather just use what I have.

    Anyone done this before?
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    You can use a positive regulator and a PNP; or you can use a negative regulator and an NPN. Or you can buy a 3A adjustable positive regulator. I would buy the negative adjustable regulator similar to the LM317, and add the external NPN. This has the advantage in that the collector of the NPN can be grounded without using a mounting kit.
    Last edited: Feb 28, 2010