AC motor drive from single-ended supply

[PRR]

Originally Posted by Airprodigy

...However a quadrature oscillator requires 3 RC segments whereas this only appears to have 2 ....

I agree. 2 can work only at infinity. In practice two obvious poles won't sing, but one more much higher pole will bring it to the sing point, but with poor control of frequency.

The Quadrature Oscillator

https://backend.orbit.dtu.dk/ws/port...P-F4-9047p.pdf

It is always possible the drawing is incomplete. Or that the amplitude control (Zener thing) hides a pole.

[msdin]

Originally Posted by Airprodigy

I realise the circuit contains an RC oscillator . However I am a bit puzzled - it seems to most closely resemble a quadrature oscillator using the two top left op amps. However a quadrature oscillator requires 3 RC segments whereas this only appears to have 2 ( consisting of the 1% toleranced caps and resistors, I assume). I'm obviously missing something here!

Sorry my mistake.
I've notice the TD320 circuit is different to the Phonosophie.

The TD320 oscillator is more like a State Variable Filter Oscillator.

ESP - Sinewaves