From: Dennis Tomlinson ([email protected])
Date: Tue May 30 2000 - 12:43:28 PDT
[email protected] wrote:
>
> My 2 cents worth:
>
> I'm not sure there IS a derivation of the .35/Tr=BW equation.
>
<snip>
R V(c)
--------/\/\/\---------
| |
---- |
|u(t)| ---
---- --- C
| |
-----------------------
|
---
-
V(c) = 1 - e^(-t/RC)
from which:
t = -RC*ln(1-V(c))
Since:
B = 1/(2*Pi*RC)
we have:
t = (-1/(2*Pi*B))*ln(1-V(c))
Tr = t(0.9) - t(0.1) = (-1/(2*Pi*B))*(ln(0.1) - ln(0.9)
Which, according to my HP32, gives:
Tr = 0.349699152563/B
or:
Tr = 0.35/B
(Close enough for SI work)
Cheers,
Dennis
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