So,we needed to create a pure sine wave oscillator for driving a 40k Hz ultrasonic driver for an insect/mosquito repellant use case. Covid19 lockdown meant that we had to use from the parts available from our stock. It turned out that we had a bucket load of LM324 from Surplectronics.com. LM324 is a great general purpose quad Op-Amp. Usually such applications make use of the LM380 power amplifier but there are issues of frequency shitfs with variation in load and the fact that components aren’t ideal and that each subsequent RC stage loads the previous one, adds to the distortion of the resultant sine wave unless it is buffered.
So the solution was to use two of the Op-Amps from LM324 for the phase shift RC oscillator and two of them for buffering the output, one in-phase and the other inverted. And they were used to drive a push-pull driver stage that then drove an ultrasonic transducer. Repelling the bugs away !