John Hansen wrote...

>        I'm attempting to use an LM317T to provide 3 volts (I need about 150
>ma).  The data sheet indicates that the voltage output is a function of the
>ratio of the value of the resistor between the ADJ pin and ground and the
>value of the resistor between output and the ADJ pin.  Unfortunately, it
>provides no information on what the order of magnitude of these resistances
>should be, just the ratio.  I've found that using a 1K resistor between ADJ
>and ground and a 680 ohm resistor between ADJ and output gives me almost
>exactly 3 volts output.  While that would seem to indicate I've got the
>ratio about right, are these reasonable values to use in this
>application?  I'm using 1/4 watt resistors.

Yes, those are reasonable values.  If you make them much smaller
than that, the resistors simply waste current unnecessarily; much
larger, and you'll begin to see the output voltage depart
noticably from the calculated value due to the non-zero current
drawn by the ADJ pin.

Dave D.

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