WIDE_RANGE_VOLTAGE_TO_FREQUENCY_CONVERTER_1

Published:2009/7/9 5:21:00 Author:May | From:SeekIC

This circuit uses a programmable op amp such as the HA2730-a two-amplifier monolithic chip with independent programming ports for each amplifter-whose slew rate and other parameters vary linearly with a so-called set current. The converter circuit uses one amplifier, A1, as a slewing amplifier and other, A2, as a comparator function. The control voltage VC, determines A1's slew rate. And, because A1's output voltage swing is constant, the modulation of its set current results in direct control of the circuit's frequency. A1's internal compensation capacitor acts as the timing component. An internal bipolar current source,whose current magnitude is directly proportional to the set current of pin 1, then determines the charge-discharge rate. A conversion nonlinearity of ±0.03% of full scale over 3 decades and ±1.5% of full scale over4.3 decades of frequency is possible. The frequency range is adjustable by a change in the resistance R.



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