FreeLists / si-list / [SI-LIST] Re: Rise time bandwidth relation

[olaney@xxxxxxxx]

Exactly correct.  This is the 3 dB bandwidth for a circuit dominated by a
single pole, based on a 10% to 90% Tr measurement.  For 20% to 80%
measurements (found on many logic data sheets), use BW ~ .22/Tr.  In the
instance of an infinite pole, all pass filter a.k.a coax cable, I've read
that BW ~ .31/Tr (10% to 90%).  Can anyone clarify the origin of THAT
number?

Thx in advance,
          Orin

On Mon, 7 May 2007 11:21:55 -0400 jaudet@xxxxxxxxxx writes:
> Based on simple RC circuit... Vo=V*(1-e^(t/RC))
> So apply it for 10% and 90% ( risetime )
> Vo at 0.1= 0.1*V =  0.1*(1-e^(t at 0.1/(RC))
> Vo at 0.9= 0.9*V =  0.9*(1-e^(t at 0.9/(RC))
> 
> tr=   t at 0.9 -  t at 0.1..... and by manipulation on previous 
> equations 
> you will find  tr = 2.2RC
> 
> fc= 1/ (2piRC).... 
> 
> so fc = 0.35/tr
> 
> 
> Jean Audet
> Electrical Analysis
> STG / World Wide Packaging & Test
> Organic and Ceramic Packages 
> IBM Bromont
> Tel: 450-534-6317, tie line: 552-6317
> E-mail: jaudet@xxxxxxxxxx
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