Return-Path: X-Spam-DCC: paranoid 1481; 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=-2.2 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, FORGED_RCVD_HELO,SPF_PASS 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 uAPDxlnE029307 for ; Fri, 25 Nov 2016 14:59:47 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1cAGz0-0001EF-2f for rs_out_1@blacksheep.org; Fri, 25 Nov 2016 13:56:06 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1cAGyz-0001E6-Ov for rsgb_lf_group@blacksheep.org; Fri, 25 Nov 2016 13:56:05 +0000 Received: from smarthost03c.mail.zen.net.uk ([212.23.1.22]) by relay1.thorcom.net with esmtp (Exim 4.87) (envelope-from ) id 1cAGyw-0003rf-5T for rsgb_lf_group@blacksheep.org; Fri, 25 Nov 2016 13:56:04 +0000 Received: from [82.70.254.222] (helo=OfficeWin7.lan) by smarthost03c.mail.zen.net.uk with esmtp (Exim 4.80) (envelope-from ) id 1cAGyv-0000a3-8g for rsgb_lf_group@blacksheep.org; Fri, 25 Nov 2016 13:56:01 +0000 Date: Fri, 25 Nov 2016 13:56:00 +0000 From: Chris Wilson Organization: Gatesgarth Developments X-Priority: 3 (Normal) Message-ID: <635074543.20161125135600@chriswilson.tv> To: rsgb_lf_group@blacksheep.org MIME-Version: 1.0 X-Originating-smarthost03c-IP: [82.70.254.222] Feedback-ID: 82.70.254.222 X-Scan-Signature: 6ffbd2c9950b634d6cc91f9565b01a8b Subject: LF: H Bridge power MOSFET based amps question Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit 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 10.1.3.11 Content-Length: 1231 Status: O X-Status: X-Keywords: X-UID: 9540 25 November 2016 I have built a 1kW Class D amp for none linear digital transmissions around 136kHz. My Dave Pick designed amp uses four MOSFETS, two in parallel each side driven by a dedicated driver chip. I see the odd LF amp design using what's described as a H Bridge MOSFET array. The one I most recall most, by Andy Talbot used rectified 240 volt single phase mains to run it. My question is why use an H Bridge rather than paralleling more MOSFETS in what to me is a more conventional format? Does it overcome voltage or current limitations? Is it due to adding more capacitance with paralleled devices? Or does it allow a linear amp to be built? I realize a meaningful reply might be quite lengthy, so I assure you I have Googled it, but most stuff related to in the articles is industrial motor control. Secondly, in a Class D none linear amp, how is the gate resistor value chosen, and is there ever a case for not using one at all? Thirdly, am I alone in thinking the terms Drain and Source seem back to front and the names would intuitively be reversed so a Drain was called a Source and vice versa? :) Thanks. 2E0ILY -- Best regards, Chris 2E0ILY mailto:chris@chriswilson.tv