RussellMc wrote:
> At the corner frequency of the first RC stage the second 10 uF has an
> impedance (of course) equal (in magnitude) to the resistance of R1, so
> C1 is loaded with a series load of 148k capacitive in series with 320k
> resistive. This loading is non trivial and will skew the result.

Right.  If you check my original message I noted this effect and advised th=
e
OP to separate the impedences of each filter by roughly a factor of 10.
That way the second filter will have negligeable loading on the first
filter.

I didn't elaborate on the particular design presented, and deliberately
limited my numbers to two significant digits, because the point was only to
show his values were "way off".  Getting into whether they are way off +-5%
or way off +-10% would have added confusion, detracted from the message, an=
d
would have been irrelevant anyway.

I expected he would come back with a design that has the glaring problem
fixed.  At that point sharpening the pencil might have been approriate, but
he never provided a updated design.

--=20
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