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PCB for teddy's 'Regulator booster'

Discussion in 'd.i.y.' started by mikesnowdon, May 20, 2010.

  1. mikesnowdon

    mikesnowdon resU deretsigeR

    Myself and Anthony (aka G&JM) have been playing with the idea of a PCB that incorporates the 'Regulator Booster' using mostly SMT parts for minimal size and allows heatsinking of the regulator itself. We wanted it to be as 'drop-in' as possible.

    We've only done 2 boards so far: A positive and a negative version using LM78** and LM79** series regulators as these seem to be the most common. If people want a 317 or 337 based version let us know in this thread. So far the boards are based on using a BC547 or 557 pass transistor. For higher current demand a BD139/140 can be used and I plan to add extra pads on he PCB so either transistor can be used on the same board (they have a different pin-out). There is also the option to have a LED power indicator. Resistors and LED are SMT case size 603. 1/4w resistors are available in this size. Tant caps are case style B allowing upto 35v rating.

    As these are small we would be looking at doing them in strips like the TeddyRegs were done so maybe 10 per strip? Let us know what ratio of positive or negative VE boards you would like.

    The main purpose of this thread is to have any possible improvements, corrections, or tweaks aired and to gauge interest with regard to a possible group buy.

    Heres the layout....

  2. mikesnowdon

    mikesnowdon resU deretsigeR

    Schematics to follow.....

    78** Positive Reg Booster:


    79** Negative Reg Booster:

  3. LoBo

    LoBo Fix it then modify it

    I'd be interested in 317 and 337 regs. A strip of each?

    This would be cool Mike. Nice one.
  4. mikesnowdon

    mikesnowdon resU deretsigeR


    Also, any ideas on the cheapest way to have these made and which company to make them?

    Thanks :)
  5. Herat

    Herat pfm Member

    I'd be interested in 317 and 337 regs too, 1 or 2 pos and neg


  6. Bemused

    Bemused What's this all about then?

    Hi Mike, I have to be real stupid here and say I thought the booster was to get more current out of the regulator, but looking at your circuit the regulator still carries all the load.
    What have I missed.
  7. PigletsDad

    PigletsDad pfm Member

    It boosts the rejection ratio, especially at high frequencies where the 3 terminal devices fall away.
  8. martin clark

    martin clark pinko bodger

  9. martin clark

    martin clark pinko bodger

    Mike, do note for reasons of voltage drop and limited collector current that really will only be good for load currents under 50mA.
  10. mikesnowdon

    mikesnowdon resU deretsigeR

    I have used this circuit on the 4 local 7805's powering my DAC chips and the effect wasn't subtle ;)
  11. mikesnowdon

    mikesnowdon resU deretsigeR

    Unless a smaller resistor and appropriate pass transistor is used?
  12. mikesnowdon

    mikesnowdon resU deretsigeR

    The idea is that the user can increase C2 and reduce R1 and sub the BC547C for a BD139. Then bolt the reg to a heatsink and all is good for higher current applications. Or leave it standard for lower current applications, circa <50mV.

    Am I missing something?
  13. martin clark

    martin clark pinko bodger

    No, that'll work nicely :)
  14. neiljadman

    neiljadman Senior Member

    Mike I see you used Expresspcb software. That locks you in to using Expresspcb for manufacturing since it is their own proprietary program. If you want to go outside ExpressPCB you'll need to redo the layout in a software that exports gerber files.

    The only way to get the gerbers from Expresspcb is to pay them to send you the files - which they will do for about $60 - but only after you have placed a first order.
  15. neiljadman

    neiljadman Senior Member

    Also, why not go the whole way and use a BC847C/BC857C? The SOT23 packages are readily available and very compact.

    I'm not sure if there's a SMT equivalent for the BD139 though...
  16. 337alant

    337alant Negatively Biased

    Hi Mike
    I would be interested in 2 strips of each
    Great idea and thanks ;)

  17. Bemused

    Bemused What's this all about then?

    Thank PD and Martin.

    Mike, I would be interested in a few strips
  18. mikesnowdon

    mikesnowdon resU deretsigeR

    ^^ What type of regulator would you prefer guys?
  19. mikesnowdon

    mikesnowdon resU deretsigeR

    Nice idea. It depends on the current rating. I'd like to make these as universal as possible. I wonder if there is a SMT transistor that would allow upto 500mA?
  20. mikesnowdon

    mikesnowdon resU deretsigeR

    While were at it is there anything simple that we could do to further improve the output of the reg? Im wondering if its worth adding some kind of L/C on the reg output to filter any noise generated in the regulator itself, or at least ensure its nice and stable?

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