Sjöström Audio DIY forum

Projects => Power supplies => Topic started by: Water Damage Florida on February 24, 2011, 02:59:00 PM

Title: Noise performance LM2940CT-12 LDO regulator
Post by: Water Damage Florida on February 24, 2011, 02:59:00 PM
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.
Title: Re: Noise performance LM2940CT-12 LDO regulator
Post by: peranders on February 25, 2011, 01:38:07 PM
LM317 isn't so bad after all.
Title: Re: Noise performance LM2940CT-12 LDO regulator
Post by: Fokko on May 09, 2011, 10:18:49 AM
So using a LT1085, instead of a LM317, in a Jung regulator, would increase the performance.
Title: Re: Noise performance LM2940CT-12 LDO regulator
Post by: peranders on May 09, 2011, 05:23:08 PM
Sorry,  I have no idea but I can't imagine you'll get worse performance.