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Sender: "piclist-bounces@mit.edu" Date: Sat, 27 Feb 2021 06:55:29 -0800 Subject: =?Windows-1252?Q?Re:_[EE]::Turn_negative_regulator_=09=E2=80=9Cupside-dow?= =?Windows-1252?Q?n=E2=80=9D_to_c_reate_bipolar_=09supply_from_single_sour?= =?Windows-1252?Q?ce?= Thread-Topic: =?Windows-1252?Q?[EE]::Turn_negative_regulator_=09=E2=80=9Cupside-down=E2?= =?Windows-1252?Q?=80=9D_to_c_reate_bipolar_=09supply_from_single_source?= Thread-Index: AdcNGgIlOGJVqI0ASCimFb446DMVFg== Message-ID: <7.0.0.16.2.20210227094853.092f1278@interlog.com> References: List-Help: List-Subscribe: , List-Unsubscribe: , In-Reply-To: Reply-To: Microcontroller discussion list - Public. Accept-Language: en-US X-MS-Exchange-Organization-AuthAs: Anonymous X-MS-Exchange-Organization-AuthSource: TS500.efplus4.local X-MS-Has-Attach: X-Auto-Response-Suppress: All X-MS-Exchange-Organization-SenderIdResult: Pass X-MS-Exchange-Organization-PRD: mit.edu X-MS-TNEF-Correlator: received-spf: Pass (protection.outlook.com: domain of interlog.com designates 208.85.220.69 as permitted sender) receiver=protection.outlook.com; client-ip=208.85.220.69; helo=mail-1.ca.inter.net; dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mitprod.onmicrosoft.com; s=selector2-mitprod-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=ebVn+oogBY1aHvOGCchgsDvgTzoEPDt/KyvpAOiSPnI=; b=kd80oFa7lDqJpJG/tI9lddmw7Z1M2kkCat/dfLDs+aOCZJW678pLgVVZ9wPpJO76eE66I9PTCuIuaQIkvbybSHDI5VSLDkopqzOwRCy8VudsSki9ox62a+fibT+vJj+cRVzMbt3NQcIR0e7knKTq5P3yw1qJs/HOFutZrk7bWTw= authentication-results: spf=pass (sender IP is 208.85.220.69) smtp.mailfrom=interlog.com; mit.edu; dkim=none (message not signed) header.d=none;mit.edu; dmarc=bestguesspass action=none header.from=interlog.com; errors-to: piclist-bounces@mit.edu list-id: "Microcontroller discussion list - Public." list-post: x-beenthere: piclist@mit.edu x-mailman-version: 2.1.6 x-topics: [EE] Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 At 07:23 AM 2/27/2021, you wrote: >While this idea is 'obvious in retrospect' it is also useful and 'clever'. > >The circuit uses a single negative regulator to provide a regulated >POSITIVE supply plus an unregulated supply of -(Vin - Vout) > >Many single supply circuits would benefit from having a negative supply. >This often does not need to be well (or at all) regulated or to have a >particular value. >For many notionally single supply opamps, having a whiff of negative suppl= y >rail can convert "sort of pulls down to ground" into a solid ground >output. >Providing an unregulated varying and possibly noisy negative supply has >potential implications for supply noise rejection and other issues, but is >still of potential value in many cases. > > >https://www.edn.com/turn-negative-regulator-upside-down-to-create-bipolar-= supply-from-single-source/ > >[image: image.png] > >An even more "Heath Robinson" solution is to provide a forward biased diod= e >in the ground return of all circuitry and to use the !~=3D 0.6V drop to >provide a -0.6V negative supply. It works :-). Regulators such as the LM7805 have a fairly constant ~5mA current=20 flowing out of the GND pin which can be used in such a way, with a regular diode, a Schott= ky, a zener, a TL431 or an LED. Of course usually you need ground to be common with something or other or t= he wasted power is too great so you end up using a 10-cent 7660 or whatever. --sp =20 --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .