Dear SherlockBenedict
Hi
Why you don't calculate it ? how do you found that formula ? simply you can demonstrate it ! ( certainly for N section it will not be simply ! but it will be funny ! )
Best Wishes
Goldsmith
On a slightly unrelated note, you can get a low distortion sine wave oscillator by swapping the positions of the resistors and capacitors as in the circuit below.
The second pic shows the outputs of the two opamps. As expected the output of the 2'nd opamp is badly clipped because the loop gain is higher than needed, but the output of the first opamp is a good looking sine wave with less than 1% distortion.
The trick is that the phase shift network also acts as a low pass filter to remove most of the distortion. I'm surprized that the conventional arrangement is so popular and this variation is seldom, if ever, mentioned.
It can also be used with simple one transistor oscillators. In that case distortion isn't improved but biasing is easier, resulting in lower parts count.
Hi Baas Rietrot, I am afraid that you have mentioned the link and its content without any proof by yourself.
As mentioned already by FvM (your second link) the formula with SQRT(2n) is false.
More than that, also the circuit as given in link#1 does obviously not work.
On a slightly unrelated note, you can get a low distortion sine wave oscillator by swapping the positions of the resistors and capacitors as in the circuit below.
Hey godfreyl,
yes, it is a circuit which works rather good - and probably you know that there are other oscillator topologies that exploits the filtering capabilities of the frequency determining network.
But one question: Why do you propose such a large gain ? (32 instead of 29.5 or 30)?