Linear power supply with ultra low noise - Page 1
Forum section: electronics / general

author: IRFP
author_rank: Contributor
timestamp: January 11, 2022, 07:48:19 pm
content: Hello,I am looking for schematics or ideas for the design of a linear power supply with ultra low noise (max 10uV RMS)Voltage 18 to 20 V DC / Current 200 mAThank you for your feedback

author: ch_scr
author_rank: Frequent Contributor
timestamp: January 11, 2022, 07:54:26 pm
content: I guess this is a obvious starting point?https://wenzel.com/documents/finesse.htmlI built one after doing ltspice simulation, it works well and their circuit description is pretty good.

author: Echo88
author_rank: Frequent Contributor
timestamp: January 11, 2022, 08:37:21 pm
content: Another approach:Unfortunately the LT3042/3045 itself only is capable of Vin 20Vmax and Vout 15Vmax.But using a dual secondary transformer + rectifier + caps + LT3042/3045-stage, one could connect the (galvanically isolated) LDO outputs in series to give a maximum of 30Vout at the required current and get the low noise spec.Use a stereo potentiometer for simultaneous voltage/current-setting of both LDO-stages.

author: David Hess
author_rank: Super Contributor
timestamp: January 11, 2022, 08:58:23 pm
content: Quote from: IRFP on January 11, 2022, 07:48:19 pmDo you mean with a fixed output? The design shown below easily meets your noise requirements. A PNP bipolar transistor can replace the JFET, a 7805 replaces the LM109, and an OP-07 or similar operational amplifier will provide low noise. I like using the LM329 for a reference because of its low noise but there are lots of options.

author: IRFP
author_rank: Contributor
timestamp: January 11, 2022, 09:44:59 pm
content: The document SCP-LT3045-1-EVAL indicates a possible output voltage of 19.5 V with R3 = 196 KSee the PDF.

author: trobbins
author_rank: Frequent Contributor
timestamp: January 11, 2022, 10:38:25 pm
content: Elvee also takes on that application at diyaudio:https://www.diyaudio.com/community/threads/d-noizator-a-magic-active-noise-canceller-to-retrofit-upgrade-any-317-based-v-reg.331491/

author: 1audio
author_rank: Frequent Contributor
timestamp: January 12, 2022, 06:08:34 am
content: Here is a very low noise power supply I put together:https://www.diyaudio.com/community/threads/open-source-usb-interface-audio-widget.185761/post-2810970However its dynamics are not great. Its intended for applications (like crystal oscillators) that are not dynamic. The noise is around .5 nV/rtHz depending on the transistor.

author: alm
author_rank: Super Contributor
timestamp: January 12, 2022, 09:52:21 am
content: This design should also be quite low noise:https://www.eevblog.com/forum/beginners/how-does-blackdog_s-psu-work/

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: January 12, 2022, 03:47:46 pm
content: I use the AMB Laboratories sigma 22.https://www.amb.org/audio/sigma22/It has less than 10uV (measured) at +- 30Volts so at +-15 volts it is typically going to be less, probably less than 5uV.You can assemble as a kit or try ebay. I tweaked mine with an LM399 as the zener.Randall.

author: bnz
author_rank: Regular Contributor
timestamp: January 12, 2022, 04:13:00 pm
content: Here,https://www.diyaudio.com/community/threads/triple-outputs-160w-lab-psu-epsux3-version-2.263471/, is a DIY project that comes near the requirements (30uV noise) at full power (3A), so there are chances it will meet it at 200mA.Unforunately the group buy failed, so it is not available for purchase, but there are details on its construction in the thread.

author: IRFP
author_rank: Contributor
timestamp: March 05, 2022, 11:45:24 am
content: Hello,Is it possible to reduce the noise of a power supply by cascading several control stages?Thank you for your feedback

author: picburner
author_rank: Frequent Contributor
timestamp: March 05, 2022, 01:29:11 pm
content: There are the ldo regulators produced by TI also, TPS7A47 and TPS7A33, suitable to replace 78xx and 79xx with 36Vin Max, 1A out and 4 µVRMS noise.On ebay you will find complete TO220 like populated pcbs ready.

author: branadic
author_rank: Super Contributor
timestamp: March 05, 2022, 03:21:38 pm
content: You can check the threadUltra Low Noise Lab Power Supply Extender for your existing lab supply-branadic-

author: mawyatt
author_rank: Super Contributor
timestamp: March 05, 2022, 04:01:13 pm
content: Quote from: IRFP on January 11, 2022, 07:48:19 pmTake a look at Analog Devices, the LT3045 might be useful!!https://www.analog.com/media/en/technical-documentation/data-sheets/30451fa.pdfBest,