lm317 circuit caps ?

[tomek]

Hi,
On the "standard" 317 circuit one can (should) use three caps - one across input, one across output and one on the adjust leg. Naim use only two tantal caps, Les is using Panasonic caps.
Does it make sense to use some caps like oscon or silmic around lm317, and if yes, which cap is the most important (output, input or adjust) ?

Cheers, Tomek

 

[Jiiim]

Do not use low impedance caps like oscons - the regulator doesnt like them and can throw a hissy fit.

 

[yairf]

On the "standard" 317 circuit one can (should) use three caps

The reason for using Tants is manufacturer recommendations - take a look at the data sheet (the one from National explains it best) - the impedance of the Tants is accounted for in the internal feeback loop of the 317.
The reason Naim uses only two in the High-Cap, is the fact that the 317 sees the main smoothing caps in its inputs.
Yair