How to read frequency into voltage with Arduino with an external source of frequency of 0-1Khz max?
In the past I used the LM2917 for this purpose:
That IC is a frequency to voltage converter, so it perfectly suits your need. According to some quick calculations I made it can go to some tens of kHz, so if your signal is up to 1kHz it should be fine.
Now, this is the answer to your question. But... You can easily read the frequency directly with the arduino... If your purpose was to read the frequency, I suggest you to read something about the X-Y problem