I have to analyze the following circuit and understand its function.
As far as I understand the top part is the simple phase-shift oscillator generating output sine wave at circa 145kHz.
The NE555 is an monostable(?) multivibrator that generates square pulse. But what about transistors between them?
It looks like a Darlington circuit but I'm not sure and I also don't know how it works.
Does anyone have any ideas or suggestions?
Some pictures of the simulation in LTspice below: