X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f
X-Recipient: geda-user AT delorie DOT com
X-Originating-IP: 88.129.21.118
Subject: Re: [geda-user] Variable voltage supply from fixed -- found
 distributor mark fixed but are adjustable
To: geda-user AT delorie DOT com
References: <84c207a9-df84-c244-96ee-b7e05795d491 AT nksb DOT online>
 <CAGBFkM3fXPqKpsQtd87sYc7wm+-=Qvq-7aY1f+6-A2V3UxvbNw AT mail DOT gmail DOT com>
From: "Nicklas SB Karlsson (nk AT nksb DOT online) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Message-ID: <0292d06b-6e36-e725-12c0-6c107928993c@nksb.online>
Date: Tue, 15 Dec 2020 06:48:26 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.5.1
MIME-Version: 1.0
In-Reply-To: <CAGBFkM3fXPqKpsQtd87sYc7wm+-=Qvq-7aY1f+6-A2V3UxvbNw@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Reply-To: geda-user AT delorie DOT com
Errors-To: nobody AT delorie DOT com
X-Mailing-List: geda-user AT delorie DOT com
X-Unsubscribes-To: listserv AT delorie DOT com
Precedence: bulk

Assumed those distributor marked as fixed where fixed voltage but 
reading datasheet I found some of the really are adjustable with an 
extra pin, easy to come by and plenty in stock.

Den 2020-12-15 kl. 02:24, skrev gene glick (geneglick AT optonline DOT net) 
[via geda-user AT delorie DOT com]:
> I've done some of all that. For now, I'll assume you want a positive 
> supply
>
> TL431 is a personal favorite. It works very well as a shunt regulator 
> or with a transistor to form a higher current series regulator. Both 
> good...depends on the application.
>
> You did not mention noise or temperature. If noise is important to 
> you, then you'll need to find a regulator that exposes the voltage 
> reference so you can filter it. Temperature can affect some of these 
> regulators. I've run the TL431 to 175C (and higher) with no problems. 
> The band-gap reference is really very stable. Some regulators have 
> thermal shutdown at 160C.
>
> Zener references are noisy, if that matters for you. If not, zener + 
> pass transistor is an okay option. I suspect zener's are not thermally 
> stable at high temperatures.
>
> You can always roll your own with an opamp, a pass transistor, and a 
> reference. That's pretty much what is inside the TL431 anyway. :D
>
> Also, if you look at the data sheet for any of the 3-pin fixed 
> regulators - I'm pretty sure they show ways to raise the output with 
> either some resistors or zener diodes. I haven't tried this, however.
>
> For low power, it's hard to beat SOT23 TL431 + SOT23 2N2222 + a couple 
> resistors. Very small, very flexible.
>
> Hope that helps.
>
> gene