Who did know the way to count the output frequence of the VCO?Can whom Know that show us a expression? f=?
My translation of this is, "Who knows how to calculate the output frequency of the VCO?"
If you make several simplifying assumptions:
1. The comparator op amp (the one on the right) has rail-to-rail output,
2. Vce(sat) of the transistor is zero volts,
3. the transistor has zero storage time,
4. the comparator op amp has zero recovery time from saturation,
then the frequency is
F = 3*Vc/(4*Vcc*R*C) .
This is pretty accurate for low frequencies and high control voltages. For high frequencies, the recovery and storage times become significant. For low control voltages, the Vce(sat) becomes significant. What is considered significant is up to the user.
An LM324 does not have rail-to-rail output. If you use it, the equation could still be calculated, but it would be even more approximate than the one above.