[sdiy] Dumb math question

[David Reichert]

What you say is true if he's looking for the average value of input
signals over time, but I think he's just looking for the average value
of three instantaneous values, which he will indeed get with the adder
with an attenuation factor of three.

-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of James Patchell
Sent: April 26, 2004 9:09 PM
To: jbv; synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Dumb math question

No, it would be the sum divided by three....to get an average, you need
to 
keep a running sum, which would mean an integrator would need to be in
the 
circuit...gee....actually just adding a capacitor in the feed back loop 
will do this....as long as the signals are higher in frequency than the 
cutoff frequency, you will get sort of an average.

At 04:31 PM 4/26/2004 +0200, jbv wrote:
>Consider a 3 inputs mixer built around an op-amp,
>with a gain attenuation by a factor of 3.
>Can the output be considered as the average of the
>inputs, like in maths one can calculate the average
>of 3 values ?
>
>Thanks,
>JB

         -Jim
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