Return-Path: Received: from mtain-md03.r1000.mx.aol.com (mtain-md03.r1000.mx.aol.com [172.29.96.87]) by air-dc03.mail.aol.com (v129.4) with ESMTP id MAILINDC031-85ff4d2f27ed1c; Thu, 13 Jan 2011 11:27:25 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-md03.r1000.mx.aol.com (Internet Inbound) with ESMTP id 8B68F380000B7; Thu, 13 Jan 2011 11:27:24 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PdPzt-00079P-LV for rs_out_1@blacksheep.org; Thu, 13 Jan 2011 16:26:01 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PdPzs-00079G-Bp for rsgb_lf_group@blacksheep.org; Thu, 13 Jan 2011 16:26:00 +0000 Received: from out1.ip03ir2.opaltelecom.net ([62.24.128.239]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PdPzq-0008Cn-OK for rsgb_lf_group@blacksheep.org; Thu, 13 Jan 2011 16:26:00 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AjQFAO+1Lk1cHYxR/2dsb2JhbACSGwOSKnO9C4JsgmAEjkw X-IronPort-AV: E=Sophos;i="4.60,318,1291593600"; d="scan'208,217";a="333823563" Received: from unknown (HELO xphd97xgq27nyf) ([92.29.140.81]) by out1.ip03ir2.opaltelecom.net with SMTP; 13 Jan 2011 16:25:51 +0000 Message-ID: <003801cbb33e$8b59e620$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: "rsgb" Date: Thu, 13 Jan 2011 16:25:51 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: FET RDS Content-Type: multipart/alternative; boundary="----=_NextPart_000_0035_01CBB33E.8AFF6A10" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,HTML_MESSAGE autolearn=no version=2.63 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-aol-global-disposition: G x-aol-sid: 3039ac1d60574d2f27ec5010 X-AOL-IP: 195.171.43.25 ------=_NextPart_000_0035_01CBB33E.8AFF6A10 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable LF/MF It seems to me if you are working with low V high current FETS the RDS= seems reasonable 0.02 for example but when a High V low current devic= e is need the RDS of these devices seem to be around 0.4 considerably= higher.=20 therefore the efficiency of the amplifier will never reach the 90% plu= s that some claim. I stripped a plasma tv recently and found banks of FETS (6 per bank)= and wondered why the application neederd so many and have come to the= conclusion that because of the high RDS lots were required in paralle= l to reduce the losses. Maybe there are low RDS fets about that will handle several hundred vo= lts at modest currents ie 10A at 1000 volts Room for thought de mal/g3kev ------=_NextPart_000_0035_01CBB33E.8AFF6A10 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
LF/MF
It seems to me if you are working wit= h low V high=20 current FETS the RDS seems reasonable 0.02 for example but when a High= V low=20 current device is need the RDS of these devices seem to be around 0.4= =20 considerably higher.
therefore the efficiency of the ampli= fier will=20 never reach the 90% plus that some claim.
I stripped a plasma tv recently and= found banks of=20 FETS (6 per bank) and wondered why the application neederd so many and= have come=20 to the conclusion that because of the high RDS lots were required in= parallel to=20 reduce the losses.
Maybe there are low RDS fets about th= at will handle=20 several hundred volts at modest currents ie 10A at 1000 volts
Room for thought
 
de mal/g3kev
 
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