/diy/ - Do It Yourself

Why do opamp relaxation oscillators have this startup time area? I'm trying to get audio frequencies out of them, but with 1s startup at 20Hz I can't see it as ideal, and this is both with 1 10n cap and 10µ cap with appropriate R values. Also I'm not quite getting the frequency I'm calculating (21Hz instead of 16.8Hz in this case, and 10.6kHz instead of 30.3kHz), which I assume is due to the opamp not being rail-to-rail or some other imperfection with it. Now I understand that this primitive oscillator has its limits and is expected to display unideal characteristics, but I just want to be able to plan around them, both for spice and IRL.