Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dk02.r1000.mx.aol.com (Internet Inbound) with ESMTP id A715F3800009C; Sat, 3 Dec 2011 13:45:29 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1RWuZe-0001vG-Dv for rs_out_1@blacksheep.org; Sat, 03 Dec 2011 18:44:34 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1RWuZe-0001v7-1K for rsgb_lf_group@blacksheep.org; Sat, 03 Dec 2011 18:44:34 +0000 Received: from mail-iy0-f171.google.com ([209.85.210.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1RWuZa-0006qX-Oa for rsgb_lf_group@blacksheep.org; Sat, 03 Dec 2011 18:44:34 +0000 Received: by iaen33 with SMTP id n33so8802576iae.16 for ; Sat, 03 Dec 2011 10:44:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; bh=igecRT1fjHBGBAt4GG08TfrH8oWluHu4uRBrzStOfYY=; b=ENz5f1ohJFV5vETXXJX3zFYIDo7xtxh9lGEvvenPTUVVqOksvYkA27i7cUMmYBpwoK JRozKaz2/SHvH29BGzjzro2GgqrLjY0WOLdyd/gGRaAmoypOTpVXZXrtXX6v5TPJIJIo P959/eBMhxqv5CuYubMPQPWThq599ji/WkDWI= MIME-Version: 1.0 Received: by 10.42.154.7 with SMTP id o7mr3729297icw.48.1322937863910; Sat, 03 Dec 2011 10:44:23 -0800 (PST) Received: by 10.231.200.140 with HTTP; Sat, 3 Dec 2011 10:44:23 -0800 (PST) In-Reply-To: References: <80A163C9035C44FBA23C7501118A6FDF@JimPC> Date: Sat, 3 Dec 2011 18:44:23 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: 16 bit vs 24 bit ADC? Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none 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-SCOLL-SCORE: 0:2:465088128:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d023.2 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1db4064eda6e49251a X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none When you add non coherent sources like noise, you have to add power, or mean square values. So a Noise voltage of RMS =3D 16 (the input noise) added to noise of RMS =3D 1 (Nq) =3D SQRT(16 * 16 + 1 * 1) =3D RMS noiise voltage but power =3D RMS Squared, So ignoring the SQRT and taking 10.LOG of the sum of squares goes direct to the answer in dB And resistance is always assumed to be unity in relative calculations like this - everything is normalised. Andy G4JNT On 3 December 2011 13:29, wrote: > Hi Andy, > > A silly question from someone struggling to understand, =A0but the ^2 bel= ow, > 20log... and V^2/R (for ex) =A0are all related ? =A0We're looking at volt= ages > and comparing powers? > > >> noise, it will increase the overall in the ratio >> (1 + 16^2) =A0/ 16^2 =3D 257 / 256 or by about 0.017dB. >> > > Joe vo1na > > This electronic communication is governed by the terms and conditions at > http://www.mun.ca/cc/policies/electronic_communications_disclaimer_2011.p= hp >