sine wave notches
I'm prototyping a sine wave generator using AD8620(dual, low noise, high bandwidth(+/-) ) op amp. The 'A' side is a relaxation oscillator and 'B' side is a Sallen-Keys LPF.
Well, the first .jpg attachment herein is initial circuit(using 10uF caps. where the supply connects to breadboard(+ and - ), the top image is output of first stage and lower is the sine wave o/p. WHAT is producing the square wave's distortion AND the notches in the sine wave(did improve with the power supply filtering mentioned above) ?
Now, I put a 0.1uF cap. between output of first stage and ground, and low and behold the notches improved as in the second attachment. I understand why the 'square wave' has become triangular, but HOW did the cap. get rid(nearly) of the notches, and WHY is the frequency now so much lower?
Thank you.