FREQUENCY_TO_VOLTAGE_CONVERTERS

Published:2009/7/1 1:58:00 Author:May | From:SeekIC

In these applications, a pulse input at fIN is differentiated by a C-R network and the negative-going edge at pin 6 causes the input comparator to trigger the timer circuit.Just as with a V-to-F converter, the average current flowing out of pin 1 is IAVERAGE = i x (1.1 R1C1) x f. In this simple circuit, this current is filtered in the network Rt = 100 k ohm and 1 μF. The ripple will be less than 10 mV peak, but the response will be slow, with a 0.1 second time constant, and settling of 0.7 second to 0.1% accuracy.In the precision circuit，an operatiot amplifier provides a buffered outputand also acts as a 2-pole filter.The ripple will be less than 5 mV peak forall frequenciesabove 1 kHz，and the response time will be much quicker than in Part 1，However，for input frequencies below 200 Hz，this circuit will have worse ripple than the figure。The engineering of the filter time-constants to get adequate response and small enough ripple simply requlres a study of the compromises to be made.Inherently V-to-Fconverter response can be fast， but F-to-Ⅴ response cannot．



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