Noise performance LM2940CT-12 LDO regulator

[Water Damage Florida]

heaveno,
Just for sharing
Because it is interesting and also because somebody ask me, i continue
to make some regulators noise measurements.

I have test the noise performance of :
LM317 (Motorola)
LT1085CT (LT)
LM2940CT-12 LDO regulator (NationalSemi)

The measurements methodology is same of my previous post.
(Vout=15V unless otherwise specified Rload=100 Ohms)

Results are (10Hz-100kHz bandwidth) :

LM317 -- 55µVrms
LM2940CT12 -- 190µVrms (Vout=12V)
LT1085 -- 40µVms

These results show that the LM2940 série (Low dropout regulator) are the worst !
Finally for low budget, the best choice seem to be the LM317 with large decoupling capacitor in ref input.

[peranders]

LM317 isn't so bad after all.

[Fokko]

So using a LT1085, instead of a LM317, in a Jung regulator, would increase the performance.

[peranders]

Sorry,  I have no idea but I can't imagine you'll get worse performance.