Very Low Quiescent Regulator - Page 1
Forum section: electronics / projects

author: Mike Warren
author_rank: Unknown
timestamp: August 11, 2020, 03:31:56 am
content: Either my Google skills are not working today or nothing close to what I want exists.In a perfect world, this is what I want:- 5V output (anything from 3 to 5V would be fine)- Very low quiescent current- At least 10mA (I may get away with 6mA)- Output voltage within +/- 10%- Can handle up to 30V input- Low dropout- No external components (apart from decoupling caps)- Surface mount (preferably SOT23 or similar)- Sub $2 (cheaper the better)- Easily sourcedDoes anyone know of a part that at meets most of these specs?I have successfully used an LM358 and zener in the past. regulation wasn't too critical in that case, and the same here. That was the best solution for that project because I also needed a level converter and the other channel of the LM358 did that job.

author: BrianHG
author_rank: Super Contributor
timestamp: August 11, 2020, 03:48:13 am
content: Quote from: blueskull on August 11, 2020, 03:32:34 am1uA is pretty high.If you need low quiescent current, and 0v dropout, a simple 30v-50v n-channel JFet would get the job done with quiescent current in the pA or fentoamps. Though, the regulation is a little worse. One of my old projects which targeted 3.0v left me with and acceptable 2.9 to 3.1v output within a hundred JFets. They were excellent regulating 2x CR1616 I had mounted in wearable electronic glasses.Careful, the VGS is different between JFet types. The cheapest 8cent ones usually work best.Some Jfets go as high 7v while many part # operate between 4v & 5v.

author: Mike Warren
author_rank: Unknown
timestamp: August 11, 2020, 04:41:11 am
content: Quote from: blueskull on August 11, 2020, 03:32:34 amThanks.

author: Mike Warren
author_rank: Unknown
timestamp: August 11, 2020, 04:42:28 am
content: Quote from: BrianHG on August 11, 2020, 03:48:13 amThanks for your reply. I've never done that. Do you have a link to a circuit?

author: Andreas
author_rank: Super Contributor
timestamp: August 11, 2020, 05:05:08 am
content: Quote from: BrianHG on August 11, 2020, 03:48:13 amHello,which JFets did you use for 6-10 mA?In one of my cirquits I use a BF245C / BF545C to get around 4 V with up to 25V input.My load is around 1 mA peak.But I would not load a BF245C with more than 3 mA since the voltage drops with increasing load.The bad thing is that JFets are getting more and more obsolete.with best regardsAndreas

author: BrianHG
author_rank: Super Contributor
timestamp: April 19, 2022, 09:09:18 pm
content: Quote from: Mike Warren on August 11, 2020, 04:42:28 amSomebody else just asked in a PM, so, here was my answer:Quote

author: Andreas
author_rank: Super Contributor
timestamp: April 22, 2022, 07:38:25 am
content: Quote from: Mike Warren on August 11, 2020, 04:42:28 amI am using this within my battery monitor in AD587LW cirquithttps://www.eevblog.com/forum/metrology/ad587lw-10v-precision-travel-standard/msg1449488/#msg1449488See:https://www.eevblog.com/forum/metrology/ad587lw-10v-precision-travel-standard/?action=dlattach;attach=402886Essential is to use at least 100nF on input and output in case of the FET.There is a laternative population with a XC6216 regulator (which needs 1uF)with best regardsAndreas