vco inverter
someone that has designed a ring vco and could help me.
Since the operation frequency of a inverter-based VCO is
f=1/n(tPHL+tPLH)
where:
n=number of stages
tPHL=propagation time high-to-low
tPLH=propagation time low-to-high
The propagation times depend on the capacitance viewed in each node of the ring.
I've read that the inverter passes through different regions (cutoff, saturation), so how can calculate the capacitances of an inverter working in an oscillator ?