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Thread: bulding a 9vdc to 5vdc regulator

  1. #1 bulding a 9vdc to 5vdc regulator 
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    now ive been in a need to builed a portable 5vdc power source, so i decided to go with a 9v battry because its simple, and no need to MAKE MUCH ROOM FOR 4X1.5V BATTRIES(which ill also wont give the wanted result, theyl give me a 6v and i need exactly 5v), now the thing is im searching to builed a circut that will efficentlly lower the losses that for converting 5vdc to 9vdc, and NO I DONT WANT TO USE 7805 ITS NOT POWER EFFICENT and it dont work well when the voltage lowers under ~8vdc ...
    so any information on the matter will be helpful


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  3. #2  
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    I doubt that you can do much better with discrete components, although perhaps a FET output stage would be a little more efficient than the common chips. The LM140 series seems to have a bit better drop-out and quiescent current than the 78xx's. I tend to use them all interchangeably, but an exhaustive search of various regulator chip specs might turn up one that is more to your liking.


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  4. #3  
    Forum Professor Wild Cobra's Avatar
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    What about four rechargeable batteries? they have a voltage of about 1.25 volts rather than 1.5. If you are working with 74 series TTL, your requirements are +/- 0.5 volts. If you simply need no noise on the supply, that may be your best, cheapest solution.

    Exactly 5 volts? Really now, what tolerance can you have.
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  5. #4  
    Forum Professor Wild Cobra's Avatar
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    If a 9 volt battery dropping to 8 volts is your problem for an unstable 5 volts out, maybe you are drawing more current than the battery is capable of, rather than it being the regulator.

    Do you know how source and load impedance affects a circuit?
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