**From:** greg kimball (*gkimball@indra.com*)

**Date:** Tue May 30 2000 - 22:16:08 PDT

**Next message:**selvaraj subramanian : "[SI-LIST] : Selection of Characteristic Impedance - regarding"**Previous message:**Doug Brooks: "RE: [SI-LIST] : RE: Split Plane"**In reply to:**Doug Brooks: "RE: [SI-LIST] : RE: Split Plane"**Next in thread:**Dennis Tomlinson: "Re: [SI-LIST] : RE: Split Plane"**Reply:**Dennis Tomlinson: "Re: [SI-LIST] : RE: Split Plane"

Doug et al-

Has anyone extended the '0.35' rule beyond single-order systems?

Terman's

Radio Engineers Handbook talks about '0.45' for multi-order waveforms

with overshoots in the 10% range - but doesn't reference any derivation.

I'd be curious about high Q networks up to 50% for ex.

Anyone?

Regards,

Greg Kimball

Apps Engr

TI Storage Products GP

Doug Brooks wrote:

*>
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*> My 2 cents worth:
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*>
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*> I'm not sure there IS a derivation of the .35/Tr=BW equation.
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*>
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*> Here is a different, simplistic, but intuitive way to look at it. Look at
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*> the rise time of the fastest signal you have. It (closely) resembles the
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*> rise time of a sine wave. Superimpose a sine wave over that rise time so
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*> that the rising edges are congruent. The frequency of a sine wave that has
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*> the same rise time as the rise time of your signal is approximately
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*> .3/Tr. (That is because the rise time of a sine wave is approximately 30%
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*> of its period!) That is the maximum frequency you need to be able to pass
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*> in order to pass the rise time of your signal.
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*>
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*> Hence, BW is (approx) .3/Tr,
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*> sometimes expressed as .35/Tr
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*> other times expresser as 1/Pi*Tr (Pi = 3.14159...)
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*> and then sometimes approximated by other ratios close to these, perhaps
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*> allowing for a fudge factor.
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*>
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*> Doug Brooks
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*>
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*> At 09:55 AM 5/30/00 -0700, you wrote:
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*> >The equation for bandwidth .35/Tr = BW assumes a critically damped Guassian
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*> >response and 10% to 90% Tr times. Different filters (responses) will have
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*> >different constants. For example, if the response of the filter is a simple
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*> >RC filter the bandwidth will be .4545/Tr.
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*>
*

*> .
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*> ************************************************************
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*> Doug Brooks' book "Electrical Engineering for the Non-Degreed
*

*> Engineer" is now available. See our web site for details.
*

*> .
*

*> Doug Brooks, President doug@eskimo.com
*

*> UltraCAD Design, Inc. http://www.ultracad.com
*

*>
*

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**Next message:**selvaraj subramanian : "[SI-LIST] : Selection of Characteristic Impedance - regarding"**Previous message:**Doug Brooks: "RE: [SI-LIST] : RE: Split Plane"**In reply to:**Doug Brooks: "RE: [SI-LIST] : RE: Split Plane"**Next in thread:**Dennis Tomlinson: "Re: [SI-LIST] : RE: Split Plane"**Reply:**Dennis Tomlinson: "Re: [SI-LIST] : RE: Split Plane"

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