Hello,

I've plotted the required resistor values for fc = 40kHz, gain = 10, C = 33
pf, and Q values between 1:300.  From this you can see that for Q values
between 4 and 6 you get 'good' resistor values (R1 ~= 1.5K, R2 ~= 4-6K, R3
~= 500K).  I have an error in the Matlab code I was using to do this plot
when I posted my last comment.    Graphing R2 is very useful as it shows the
effect of the quadratic in the denominator.  If you care to see the plots
and can zip them up and send them to you.

Thanks for the help.

Donovan


> > and it is a bit skimpy on details and has very strict design criteria
> > (i.e. getting R1,R2,R3 to all be reasonable values is difficult unless
> > you want to go with a really small resistor for R2)
>
> I haven't worked it out exactly but if you change the caps to 1n
> or 100p then R2 would 10 * really small or 100 * really small. Yes ?
> If you changed Q or G that would also affect the resistor values
>
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