The voltage to frequency conversion circuit is the following:
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The zener diode has a zener voltage of 10V.
After calculating, the equation which describes the output oscillation frequency with relationship to the voltage Vin applied at the input, assuming Voutmax = 10V,of the circuit is:
![\color{White} \large Frequency = \frac{1}{ R_{c}C} * \frac{1}{ln(\frac{V_{in}^{2} - 20V_{in} - 300}{V_{in}^{2} - 20V_{in}})}]( "\color{White} \large Frequency = \frac{1}{ R_{c}C} * \frac{1}{ln(\frac{V_{in}^{2} - 20V_{in} - 300}{V_{in}^{2} - 20V_{in}})}")
For the given values of Rc = 10k ; C = 100n and Vin = 3V, the calculated output frequency is 518 Hz while the simulated one is 521 Hz. Not bad, the errors are probably there because of the output resistance of the op-amp. I thought of a nice method to describe and eliminate that error in the case I don't find the output resistance of the LM358.
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acp.calin
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