Precision voltage-to-frequency converter

  
In this circuit, integration is performed by using a conventional operational amplifier and feedback capacitor, CF. When the integrator's output crosses the nominal threshold level at pin 6 of the LM131, the timing cycle is initiated. The average current fed into the op amp's summing point (pin 2) is (1.1 RtCt) which is perfectly balanced with - V^/R^. In this circuit, the voltage offset of the LM131 input comparator does not affect the offset or accuracy of the V-to-F converter as it does in the stand-alone V-to-F converter, nor does the LM131 bias current or offset current.
Precision voltage-to-frequency converter - schematic

Instead, the offset voltage and offset current of the operational amplifier are the only limits on how small the signal can be accurately converted.




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