question about Frequency-to-Voltage Convertor, thanks!

[mountain]

I want transform an Frequency signal to it's corresponding Voltage signal, and the output Voltage must be proportional to the frequency of the input square wave. How Can I make it?

I had used the ADVFC32 of Analog Device, and design the circuit according to its typical application as frequency to voltage convertor. But in simulator, when the input is an square wave signal with fixed frenquency, the outout is not a fixed voltage as I expected, but somewhat sawtooth things.

How Can I obtain the output voltage expected?

Thanks!

 

[flatulent]

You need to use some form of low pass filter. Try increasing the shunt capacitor in the suggested circuit or follow it by an active low pass filter. Both of these will cause errors if your input frequency changes value frequently.