I would add to this answer that there exists a fundamental theorem (by Parseval) that, loosely stated, you can calculate the energy by integrating the power of a signal over the time axis as well as by integrating the square of the absolute value of the Fourier transform of that signal over the frequency axis.
A classical book on this subject is "The measurement of power spectra" by R.B. Blackman and J.W. Tukey. Dover Publications Inc. New York but most books about Digital Signal Processing will treat this subject as well. Harry > hi > > thermal noise from its nature is power, not voltage. > > Pn = k * T * B > k boltzmann constant 1.380662E-23 J/K (VAs/K) > T absolute Temperature (Kelvin) > B bandwidth Hz > > this power is delivered from any resistor, regardless of its > resistance. > (assumed "white", i.e. frequency independent noise) > so noise denisty is Pn/B = kT in Watts/Hz > > as power is P = U * U / R or P = I * I * R > (voltage or current squared) > > you get the sqrt of bandwidth (i.e. Hz^0.5) when you go from power to > voltage at a known resistance. > U = sqrt(P * R) > > (with "white", thermal noise the noise denity is frequency > independent. Otherwise you would have to integrate over frequency) > > regards > Alois > > > Hi all > > > > I have to fill up a knowledge gap about noise. > > > > The unit of the noise density is mostly nV/"sqrroot"HZ and I don't > > really what this likes to tell me. > > > > Anyone has a good article about this? > > > > TIA > > Edi > > > > -- > > > > > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > + IH electronic + Phone: ++41 52 320 90 00 + > > + Edi Im Hof + Fax: ++41 52 320 90 04 + > > + Doernlerstrasse 1, Sulz + URL: http://www.ihe.ch + > > + CH-8544 Rickenbach-Attikon + E-Mail: [EMAIL PROTECTED] + > > + Switzerland + + > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > -- > > Author: Edi Im Hof > > INET: [EMAIL PROTECTED] > > > > Fat City Hosting, San Diego, California -- http://www.fatcity.com > > --------------------------------------------------------------------- > > To REMOVE yourself from this mailing list, send an E-Mail message to: > > [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the > > message BODY, include a line containing: UNSUB CHIPDIR-L (or the name > > of mailing list you want to be removed from). You may also send the > > HELP command for other information (like subscribing). > > - - - - - - - - - - - - - - - - - - - - - - - - - - > Alois Bauer > WORK Microwave GmbH > Raiffeisenstr. 12, D-83607 Holzkirchen, Germany > Tel. {+49} (0)8024-6408-0 / FAX (0)8024-640840 > > -- > Author: Alois Bauer > INET: [EMAIL PROTECTED] > > Fat City Hosting, San Diego, California -- http://www.fatcity.com > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB CHIPDIR-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > -- Author: H.C. Croon INET: [EMAIL PROTECTED] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
