Why do I get a triangle wave in this Schmitt trigger oscillator?
It is supposed to be a Relaxation Oscillator , so the Square wave output on the Gate is integrated to ~ 1/3Vcc then toggles.
If you are seeing x MHz or whatever that is the unity gain bandwidth of the inverting gate in &quot;quasi&quot;- linear negative feedback mode with inadequate phase margin at unity gain.
Raise R1, 100k R2 to 330k or so will prevent that.so it doesn't load R4 and has gain&gt;1
The external bias affects both duty cycle and frequency.