Return-Path: X-Spam-DCC: paranoid 1290; 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=-2.4 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL 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 t7AGeSsk025966 for ; Mon, 10 Aug 2015 18:40:28 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ZOq4G-0005Nx-VD for rs_out_1@blacksheep.org; Mon, 10 Aug 2015 17:36:56 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ZOq4G-0005No-LI for rsgb_lf_group@blacksheep.org; Mon, 10 Aug 2015 17:36:56 +0100 Received: from mailex.mailcore.me ([94.136.40.144]) by relay1.thorcom.net with esmtp (Exim 4.86) (envelope-from ) id 1ZOq3E-0002oO-VT for rsgb_lf_group@blacksheep.org; Mon, 10 Aug 2015 17:36:55 +0100 Received: from 62-249-237-217.static.enta.net ([62.249.237.217] helo=DADPC) by mail11.atlas.pipex.net with esmtpa (Exim 4.71) (envelope-from ) id 1ZOq2y-0006vC-HX for rsgb_lf_group@blacksheep.org; Mon, 10 Aug 2015 17:35:36 +0100 From: "Michael Probert" To: References: <1892164761.20150810130954@chriswilson.tv> <7E7DFBB4D102A04DB5ADC88D66628A4A443E0BC1@ICTS-S-MBX1.luna.kuleuven.be> <1407871247.20150810162853@chriswilson.tv> In-Reply-To: <1407871247.20150810162853@chriswilson.tv> Date: Mon, 10 Aug 2015 17:35:36 +0100 Message-ID: <001301d0d38a$9658e460$c30aad20$@solva.co.uk> MIME-Version: 1.0 X-Mailer: Microsoft Outlook 15.0 Thread-Index: AQGuqWhT6vibIVbiPU7nVcIZaSCgbAHCOPWMArabzvYCy5ng8AFFuKFGAY85SBqd+PNDYA== Content-Language: en-gb X-Mailcore-Auth: 7883282 X-Mailcore-Domain: 6228 X-Scan-Signature: 9d01e9df836df8dd3868645661e1c1f7 Subject: RE: Re[2]: LF: Protecting a MOSFET driver chip from MOSFET failure? Content-Type: text/plain; charset="utf-8" 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 Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by paranoid.lipkowski.org id t7AGeSsk025966 Status: O X-Status: X-Keywords: X-UID: 3848 Hello Andy and Chris, Have been following your discussion with interest. I too experienced the "hand grenade effect" of removing the drive whilst using DC coupling. Dave YXM put me right some years ago. Thanks Andy for the further explanation. I have always been perplexed by the distortion of the gate pulse that occurs when the drain volts are applied. This sometimes appears to show up as a slight instability on tail of the drain pulse. Probably of no importance but never heard anyone mention it. Would appreciate any comments Mike -GW4HXO ___________________________________________________________________________ Subject: Re[2]: LF: Protecting a MOSFET driver chip from MOSFET failure? Hello Andy, Monday, August 10, 2015 > No, capacitive coupling with diode restorationends up with near-enough > the same voltage applied to the gate as you had in thr first place. > A 0/12v output from the driver chips ends up at -0.7 /+ 11.3 V > (assuming 0.7V diode drop) > As for the question of the dual drive with resistors. The resistors > may as well say in, just to smooth off edges and reduce dissipation in > the driver. i doubt you'll notice any difference. > Andy G4JNT OK, thanks and sorry for the naive questions, lots to learn, I was amused by my friend calling power FET's "Fire Emitting Transistors". I see his point now, they do go with a good bang and sizzle! The wife smelt them downstairs and asked wearily if it meant a longer wait before a job she attached great importance to, but I classed as a boring irrelevance, got done... -- Best regards, Chris mailto:chris@chriswilson.tv