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swapping npn for pnp

Discussion in 'General Electronics Discussion' started by messerschmitt, Oct 20, 2012.

  1. messerschmitt


    Oct 20, 2012
    Hi, found this circuit i would like to build on the net with the instructions
    "For the most stable operation replace R1 with a 1K
    tempco resistor, replace Q1 and 2 with a pnp pair
    and wrap all three pieces with heat shrink tubing"
    not sure how to change things to put pnp transistors in. I know some polarities need to be changed, can anybody help? thanks

    Attached Files:

  2. davenn

    davenn Moderator

    Sep 5, 2009
    hi there welcome to the forums :)

    Q1 and Q2 are already shown as PNP type transistors

  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    That sentence is advising you to use a device which contains a pair of matched transistors rather than two separate transistors.
  4. messerschmitt


    Oct 20, 2012
    thanks for the replies, it makes sense now, i understand why using a matched pair would help, didnt understand why using npn instead of pnp would make any difference.
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