Filter Caps with LM317

Thread Starter

damnyankee36

Joined Dec 19, 2015
13
It seems that every LM317 voltage regulator circuit I see is powered by a rectified DC input. I need a simple regulator circuit that will be powered by a battery source. Can I assume that I won't need to use any input or output capacitors in this circuit since I won't be dealing with any ripple?

Thanks!
 

AnalogKid

Joined Aug 1, 2013
8,227
No.

The capacitors also affect the stability of the regulator circuit and its output noise. In particular, if the wire length between the battery and the regulator is more than a couple of inches, an input capacitor is required as said in the datasheet.

ak
 
Last edited:

hp1729

Joined Nov 23, 2015
2,304
It seems that every LM317 voltage regulator circuit I see is powered by a rectified DC input. I need a simple regulator circuit that will be powered by a battery source. Can I assume that I won't need to use any input or output capacitors in this circuit since I won't be dealing with any ripple?

Thanks!
Running from a battery you probably will not need as much of a capacitor. On my battery powered breadboard often omit them completely if I am just using a few mA of current. 100 mA or so I might use 1 to 10 microfarads. When in doubt, use a small cap at least.
Try it and see what it does for you. Experience is almost as valuable as theory.
 
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