Re: How 3-capacitor sine generator works really?

It's a phase shift oscillator - one of many.

Thanks a lot, so the "keywords" were on the surface, I just missed. It
could be googled by
phase shift or even by RC-oscillator. Great!

Here's a solution I came up with back in 1986

Wow, thanks for curious story. I haven't yet went to school then :) Golden
age of electronics!

For oscillation you need to put the output back in phase to the input.

The tansistor gives 180 degrees phese shift
Thanks, I see I was mistaken thinking that each stage "shifts" phase by 90
degrees (obviously I forgotten university lectures) and that confused me.

and as gain is >1 it wil oscillate

supposedly, it is about overall gain - transistor gain multiplied by (less
than 1) gains of filter stages - it seems they "eat" quite a lot of an
amplitude.

The 100K base resistor was probably selected to match the

beta of the transistor
please note here is some cheat - resistor is connected not to the positive
supply but to the collector - it reduces the pull-up effect, but allows for
wider range of resistance (effectively removing necessity of adding proper
pull-down resistor at the base and small another one at emitter).

The lesson for your students is more general

Thanks, it is a good lesson for myself - as for the students, they are a
bit too beginners to
get into such depth of idea, but I'll try to communicate your explanations
:)

Another phase-shift osc form uses three RC integrators

That's curious, I'll look for this variant.
--
to email me substitute github with gmail please