Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id wAUL4hdh031617 for ; Fri, 30 Nov 2018 22:04:44 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1gSpnh-0003om-Qx for rs_out_1@blacksheep.org; Fri, 30 Nov 2018 20:54:13 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1gSpkK-0003nT-DC for rsgb_lf_group@blacksheep.org; Fri, 30 Nov 2018 20:50:44 +0000 Received: from mout.perfora.net ([74.208.4.197]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91_59-0488984) (envelope-from ) id 1gSpk6-0005Dh-Ur for rsgb_lf_group@blacksheep.org; Fri, 30 Nov 2018 20:50:31 +0000 Received: from [192.168.1.127] ([72.224.159.95]) by mrelay.perfora.net (mreueus002 [74.208.5.2]) with ESMTPA (Nemesis) id 0LjcNC-1h46N02gC8-00bc38 for ; Fri, 30 Nov 2018 21:50:26 +0100 Subject: Re: [Lowfer] LF: Re: FET change, hmmm To: rsgb_lf_group@blacksheep.org References: <2133457080.64533.1543584595217@mail2.virginmedia.com> <27270b29-dde1-1207-1158-becc1e4de123@n1bug.com> <1382885588.67051.1543589445229@mail2.virginmedia.com> <530677a9-52b1-0280-128f-4afc58f94536@n1bug.com> From: N1BUG Openpgp: preference=signencrypt Autocrypt: addr=paul@n1bug.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Provags-ID: V03:K1:bAQpljJK2p7/kq92YtNLXPi1ChjeBToFlPSyykAgqmYwICcB4Mz 39AceELuR+98fwBXUz3JbmUgzYDUZG3F147k8dFem81xIJa+cT6+0geKJVQOKIYTQx8t4v4 z0Le+F0imboxoRT/4sG4pB240vRlvrvaKSk/B5pFPRQGjVOv+bpifnFYrlDjJb0l9Ot5YGj B/HQURs7SfYc2IZmILwPg== X-Spam-Flag: NO X-UI-Out-Filterresults: notjunk:1;V03:K0:qbAhOaV/ekA=:oDiLFP8wS5S5w1GgPwtQKA ZOoL16kFumtjyAgV4d5jwkQ+sZR/M8f3hcwPE5BiBaI2EhYJuMznwJHG6rz9eWlNn9zYVa6sg 0XZ+2soyaQFwsybsnGYw0smIkLyZRww5H0ADpYO8oqS7Ch33Im2KmyRXIB1HPol/1mE+++FDx 8QYA1RWtAdNXDoiZG3AbTG/9ZfleoEwz6HB8Rb8sxflbR+9anH3KTa1Gott0zJckNC7znEm64 6QohTJEZCdcJOrgd52BUpJgM9ise86yisFOGZqyRkAUQHVz/rsC4+ZMkZSom0FNgvhYQlzfI2 gldTPVP1jVRj1x+wpI7UwR5IIi09l3XzmSLADc98yXZrt4BtPsR5R3oHUfk3F6dyrla9Du1A9 InOl315si2g8qwjYU5nJUjOw2R9VoP39PtWzbMVSRSYPEXAKToS1K7aLwPDXHstunomh+EJDx ZQweGQx7sDXbRg7i4zoJTte8SLFDyqUShPDhlVDR2OUZYUc5FYZNuVTGp4QIcCuD7zulIpPsg KJ5kUeadbWy1Ndve80wPODYUiNqlpin2UmdICR29xPox+w55Sl6XRJypbNJd/dc6vhRIL9eIf 2emzXV2Kz5+rOKf8xahorF1k0CEgmXTOi3N66UXbNMq7hpgjJY3BOw81HOhFsEEVaNZfJa7tg EES7KdX1JiRBpj51KZleH0yFw9XkZugr4jJyif6ft0SVNLqw83WP4QfxdE4BYgF6oBXQUGzLT PIF0nasfJ1tsuxivd3P+vQL3THIjNvPG71q0Oq9IPZ1jUr4dUk9Rb0rjQCQ= X-Spam-Score: -0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: All I know is this amp had very little drain ringing and worked well with FQA34N20 FETs but it is not happy with FQA32N20. I slowly increased drain voltage but at 200W out (of a kilowatt deck), there were obvious issues related to the ringing. Content analysis details: (-0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [74.208.4.197 listed in list.dnswl.org] -0.0 RCVD_IN_MSPIKE_H2 RBL: Average reputation (+2) [74.208.4.197 listed in wl.mailspike.net] -0.0 SPF_HELO_PASS SPF: HELO matches SPF record X-Scan-Signature: a6b6ffaf48fdddf1ed5c25dc4bf03ee1 X-SA-Exim-Scanned: No; SA Timed out after 180 secs 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 All I know is this amp had very little drain ringing and worked well with FQA34N20 FETs but it is not happy with FQA32N20. I slowly increased drain voltage but at 200W out (of a kilowatt deck), there were obvious issues related to the ringing. I've gone back to my old faithful 200W output Class E amp for now. I am running WSPR-2 33% 137.437. Paul On 11/30/18 3:25 PM, Andy Talbot wrote: > Cross conduction spikes can also be dealt with by inserting a bit of > inductance between top and bottom FETs of a totem pole, or in each leg of a > push-pull pair. As done in the old Decca transmitters, and I cribbed for > my 700 Watt 137 design. > The inductor absorbs the short spike and returns the energy via clamp > diodes to the supply > See http://www.g4jnt.com/137tx.pdf > > A lot simpler than worrying about generating a special drive waveform with > gaps > > Andy > www.g4jnt.com > > > > On Fri, 30 Nov 2018 at 20:19, Hans-Albrecht Haffa wrote: > >> Dear OMs, dear Paul, >> >> To prevend current spikes by cross conduction of both fets it is necesary >> to use a gate drive circuit with dead time, as used in power supplies. But >> in this case there is a no current flow time in both transistors, what may >> cause spikes in the drain circuit. Damping of oscillations in the drain >> circuit may also reached by quiescent current, not used for class D PAs. To >> load the spikes to the load is not possible in an LW-PA, like in an >> flyback-transformer of an switch mode power supply, as the load is an >> LP-Filter that filters by reflections of the applied voltage.