This LM331 voltage to frequency converter commonly used in circuit for analog to digital conversion, frequency to voltage conversion, linear frequency modulation, and many more. It provides the output pulse train at a frequency properly to the applied input voltage and can operate at 4.0V power supply and be changed output frequency from 1Hz to 100Khz, according to the datasheet.
There are several typical circuit applications using this V-F converter that can be found in the LM331 datasheet such as Precision Voltage to Frequency 100Khz Full Scale, Simple Frequency to Voltage Converter 10KHz Full-Scale, and Light Intensity to Frequency Converter.
Find Fairchild LM331 Voltage to Frequency Converter Datasheet here – http://www.datasheetcatalog.org/datasheet/fairchild/LM331.pdf
