If the output current is 50uA I'm entering the realm of "low quiescent
current". The LM317 datasheet says the quiescent current is about 1.5mA
for a Vi-Vo of about 10v.

The reason I chose the LP2981 is because it's the only regulator I found
(after a short search) that has a low Iq (65uA), outputs more than
enough current for peak loads (200mA), and can take an input supply of
>14v. There may be others that are better, but this one costs about $.35
 as well. (I just found the LP2992, answered my own questions.. EOM)


-
Martin

Apptech wrote:

> The efficiency of a regulator is Vout/Vin for Iout >> 
> Iquiescent.
> If your Iout is always 10 mA plus then efficiency is liable 
> to be about identical regardless, for any Vin that the 7805 
> will handle. Note data sheet WORST CASE carefully for 7805 
> dropout - it's surprisingly high.
> 
> More modern regulators, such as the still old LM317, while 
> still having a high dropout voltage, tend to have lower 
> effective Iq as the powering current flows from Vin to Vout, 
> and not from Vin to ground as with the 7805. Essentially 
> only reference current flows in the ground (actually adj) 
> lead.
> 
> An LM317 will generally be superior in performance to a 
> 8705.
> 
> 
>         Russell
> 
> 
> 

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