[]|[ GorE]

I am already using the Ci and Co caps as shown in the lm317's datasheet.Anything more that i can add to further improved the voltage output ?

 

[DaKi][er]

~10uF from Adj to ground

 

[]|[ GorE]

I am not using a variable voltage output (its fixed to 15V) so Cadj is not required.Right ?

 

[mono]

Quote:

Originally Posted by ]|[ GorE I am not using a variable voltage output (its fixed to 15V) so Cadj is not required.Right ?

No, it's still going to help reduce ripple. Even when it's set up as adjustable, at any one moment it is still same thing as having it fixed at any voltage, the pot is then a momentarily fixed resistance.

BTW, if you're still using that 12V wall-wart, you'd be better off aiming for a little lower than 15V. Figuring the wart produces around 16.8, a little less after diode drops, you don't have much margin left for the drop from the LM317. You'd be better off setting it to 13-14V, if not 12V, rather than 15V. This would apply to any 12V supply too, if you'd found a lower current alternative.

 

[amb]

]|[ GorE, go to the National Semiconductor website http://www.national.com
Search for LM317 and really read the datasheet. Amongst all sort of other useful info and application circuits, it will tell you that the capacitor from the adj pin to ground is for ripple reduction.

 

[peranders]

Quote:

Originally Posted by ]|[ GorE I am not using a variable voltage output (its fixed to 15V) so Cadj is not required.Right ?

I advice you to read the datasheet. There you have it mentioned. This cap lowers the gain (increasing the feedback) which results in better regulation and better ripple rejection.

 

[]|[ GorE]

If i connect the wallwart through my Voltage Stabilizer connected to my mains socket,the wallwart outputs about 17.5V . So i guess that 15V is fine as the LM317's output.
Oh and thanks for the Cadj advice.Will do that.

 

[Ikon]

tangent recommends using either a 10µF tantalum or a 100µF electrolytic in this position.

 

[Ikon]

BTW, TNT-Audio has an excellent article about optimizing the performance of LM317/LM337 -> it's very interesting how different cap values/types in the circuit influence the performance of the regulator. I also remember reading a second, even deeper article about the same subject there ...