From: Bob Blick <bobblick@outlook.com>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Wed, 4 Mar 2020 10:34:01 -0800
Subject: Re: [OT] Adjustable regulator down to 0V
Thread-Topic: [OT] Adjustable regulator down to 0V
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Build the standard circuit but add a low value resistor(like 47 or 100 ohms=
) in series with the feedback terminal. Then feed the output of a small sec=
ond regulator(it can be a low-current one, fixed 5 volts) through a resisto=
r to the feedback pin of your main regulator. It should be about 3 times th=
e value of the first resistor you added.

What you will be doing is mixing the real output with another reference to =
keep the feedback pin from going below 1.25 volts. The performance of the r=
egulator will suffer somewhat. You can add a small capacitor in parallel wi=
th the first resistor to bring the high frequency performance back. Don't m=
ake it too big. I'd try .1 uF.

Cheerful regards, Bob

________________________________________
From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> on behalf of madsci=
entistatlarge <madscientistatlarge@protonmail.com>
Sent: Wednesday, March 4, 2020 9:10 AM
To: piclist@mit.edu
Subject: [OT] Adjustable regulator down to 0V

Any recommendations for parts to build a power supply, 0-5V output at 10A? =
 I need the output to be +adjustable all the way down to 0V (100mv max, 0 b=
etter) and up to about 5V max.  I'm thinking of using something like an lm3=
38 or other linear regulator with a small negative supply for the IC so tha=
t what it thinks is 1.2V out is 0V relative to ground.  Is this a viable ap=
proach?  This is for studying electrochemistry, hence the need for the volt=
age to go all the way down to 0V.  Series diodes on the output are not acce=
ptable as this ruins regulation, and the load current will vary.  All help =
greatly appreciated.


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