Thread: bulding a 9vdc to 5vdc regulator

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

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.

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.

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?