Return-Path: X-Spam-DCC: paranoid 1356; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, FORGED_RCVD_HELO,SUBJ_RE_NUM autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id t9VH4xLp012148 for ; Sat, 31 Oct 2015 18:04:59 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ZsZXK-00051X-DW for rs_out_1@blacksheep.org; Sat, 31 Oct 2015 17:01:50 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ZsZXK-00051O-2E for rsgb_lf_group@blacksheep.org; Sat, 31 Oct 2015 17:01:50 +0000 Received: from smarthost01c.mail.zen.net.uk ([212.23.1.5]) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1ZsZWA-0002fq-Ud for rsgb_lf_group@blacksheep.org; Sat, 31 Oct 2015 17:01:48 +0000 Received: from [82.70.254.222] (helo=OfficeWin7.lan) by smarthost01c.mail.zen.net.uk with esmtp (Exim 4.80) (envelope-from ) id 1ZsZVy-0006bR-98 for rsgb_lf_group@blacksheep.org; Sat, 31 Oct 2015 17:00:26 +0000 Date: Sat, 31 Oct 2015 17:00:25 +0000 From: Chris Wilson Organization: Gatesgarth Developments X-Priority: 3 (Normal) Message-ID: <994616020.20151031170025@chriswilson.tv> To: Andy Talbot In-Reply-To: References: <1981852865.20151017122027@chriswilson.tv> <1530BFEB-9BC2-4CA2-A7A3-338629A98202@me.com> <308511169.20151029202607@chriswilson.tv> <56328B1F.2080901@posteo.de> <12510142154.20151030112719@chriswilson.tv> <5633C6F8.4080807@posteo.de> <984267409.20151031132006@chriswilson.tv> MIME-Version: 1.0 X-Originating-smarthost01c-IP: [82.70.254.222] X-Scan-Signature: 739d4fb39bd02fc5a2de5437a39bb056 Subject: Re[4]: LF: Automatic variometer circuit Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 4729 Hello Andy, Saturday, October 31, 2015 Is this what you mean? http://www.chriswilson.tv/phase-driver.jpg Thanks. > Actually, looking again at the circuit again, it is not necessary > to use an opamp in that position to define the mid rail for the > comparator reference.    Just two equal; value resistors and > oneelectrolytic decoupling the junction to ground (Definitely not > two caps to top and bottom in the original configuration shown ... think about it...)   > You only need an opamp to define a stiff mid rail voltage where > there is likely to be any significant current draw.  Or many stages > need to be referenced to it - such as a multi stage filter.    For > single stage configurations, just two resistors and a bit of decoupling is enough -- Best regards, Chris mailto:chris@chriswilson.tv