From: Doug Brooks ([email protected])
Date: Tue May 30 2000 - 14:58:29 PDT
It seems to me (by theory and also by inspection of a wave form) the
highest order harmonics are those that enable the 10%-90% rise time. The
rounded corners at the top and bottom (0%-10% and 90%-100%) are actually
much slower.
I think it is important to qualify the formula
BW=.35/Tr
as the bandwidth up to the 3dB point.
I don't argue with the definition, it's just that others may prefer a
different definition. Or, worse yet, may be thinking in terms of a
different definition without realizing it!
Nevertheless, given that qualification, the derivation is simple and tight.
Again, just my 2 cents:
Doug
At 02:06 PM 5/30/00 -0700, you wrote:
>Doug,
>
>That's fine for the risetime of an isolated edge. However, the corners at
>the top and the bottom of the waveform occur only as the result of higher
>order harmonics. If the amplifier cannot pass these harmonics then we can
>get a good timing measurement for a single edge after a long idle period,
>but successive edges of a repetitive waveform distort, and more so as the
>duty cycle varies from 50/50.
>
>Regards,
>
>
>Steve.
.
************************************************************
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.
Doug Brooks, President [email protected]
UltraCAD Design, Inc. http://www.ultracad.com
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