LM317 question

[Arthur Harrison]

The critical specification here is "dropout voltage.  
See the graph on page 4 of the .pdf file at:
http://www.national.com/ds/LM/LM117.pdf

It indicates that for a 1A load at 25 degrees C, the LM317 
requires a minimum input-output difference of about 2v, based 
on a maximum allowable sag of 100mV at the output.  
Since you have a 3v difference available, you should be okay 
with this part.  You will be dissipating 3W of heat in the regulator, 
so be sure to provide an adequate radiator.

-----Original Message-----
From: J. Larry Hendry <jlarryh at iquest.net>
To: synth-diy at mailhost.bpa.nl <synth-diy at mailhost.bpa.nl>
Date: Saturday, December 26, 1998 9:10 PM
Subject: LM317 question


>I am wanting to supply 9 +VDC @ 1 amp from a 12 VDC supply.  Would a LM317
>be a good choice for this application?  All the schematics I have found
>using a LM317 to supply an adjustable output voltage use more than 12 VDC
>as the source voltage to the LM317.
>
>Thanks,
>Larry Hendry
>
>