TPS7A4700 with higher current psu

Discussion in 'The Projects Forum' started by lew247, Jun 25, 2015.

  1. lew247

    Thread Starter Member

    Apr 23, 2010
    I want to build power supplies for 5V and 12V to replace all the "plug in" cheap switched mode power supplies for things like telephone, broadband router, external HDD, and many other items around the house.
    What I'd like to know is could I use one of the boards of fleabay that use the TPS7A4700 chip and then use tip35's or 2n3055 etc to get greater current from the circuit?
    something like the attached circuit.
    BUT instead of using a 7815, use one of the TPS7A4700 modules
    I know I'd have to bypass the diodes on the TPS7A4700 board as I'd be supplying it with dc not ac.
    I'd make 2, one for 5V and one for 12V
    I obviously wouldn't need 20A I reckon 5A would be enough.

    I want pure clean psu's for the equipment because I do a lot of listening on SDR radio's of extremely weak signals and at the moment the noise from the smps's are ruining it.

    If not has anyone got any examples of circuits that would be just as clean and simple/easy to build?
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  2. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    Adding external pass transistors to an extra low noise regulator chip wipes out the extra low noise advantage. Also, in the circuit you posted the output is not tightly regulated because there is no feedback from the main output to the 7815. For only 5 A, better and more simple to use an LM317 and an external pass transistor. There are circuits in the datasheet and in recent threads on this forum. Reasonable decoupling capacitors will get you the quiet you're seeking. What will you be using for the bulk DC supply?