Jason ,

Firstly , 2 resistors are a waste of watts , secondly any appreciable
current draw at the split will change the voltage at the split .

If I want 9v from 12v , I just use one of my 100 5v regs i got free
off parts boards---I put some cheap generic diodes in the reference
leg of the reg ( they are 7805s good for at least 1 amp .

Am LM317 to me is only worth the bother and cost$ for Variable Voltage
output power supplies . I think its only good for about 1 or so amp
anyway , if I need more current I use a power junction transistor PNP
, NPN whatever works .

tim CET MD-238

"Jason" wrote in message ...
I see all these posts wanting to go from 12v to 9vdv

I would just use 2 resistors to split the potential difference? What am I
missing why are "LM317" etc a better chocice?


"@ spam]grnetx.com" ""sean.coyle[no \"@ spam]grnetx.com" wrote in message
. ca...
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The LM317, not a very good choice;

Not Low Dropout, requires a three volt difference in i/o voltages,
however it does handle around 1.5A. Try this part #: KA278R09TU, it can
be ordered from Fairchild Semi or any one of their agents, and the good
news, is they offer free samples of it, so you can probably hook
yourself up with 5 - 10 for free . Dropout is rated at "below 0.5V"
and can handle around 2A -- This regulator has various functions such as
peak current protection, thermal shut down, overvoltage protection and
output disable function.

Datasheet: http://www.fairchildsemi.com/ds/KA/KA278R09.pdf
Product Page: http://www.fairchildsemi.com/pf/KA/KA278R09.html