LM331 Frequency to Voltage Converter

The frequency to voltage converter circuit illustrated in the schematic diagram below produces a 10 V output for 10 kHz full scale input (square waves or pulses).  The simplicity of the circuit doesn’t mean a bad performance: this circuit has linearity about 0.06% at full scale. For your note, there is a trade-off between ripple versus response time. With Cfilter at 1uF, the output ripple is about 13 mV with 0.6 s settling time. The response time will be quicker if Cfilter is decreased in the expense of increased ripple by the same factor. An increase in Cfilter produces the opposite results. Set the 5Kohm gain adjust for 10 V out with a 10 kHz input to trim.

[Circuit’s schematic diagram source: Linear Application Handbook, National Semiconductor]