ULTRA_PRECISION_INSTRUMENTATION_AMPLIFIER

Published:2009/7/7 8:35:00 Author:May | From:SeekIC

This circuit will run from a single 5 V power supply. The LTC1043 switched-capacitor instrumentation building block provides a differential-to-single-ended transition using a flying-capacitor technique. C1 alter-nately samples the differential input signal and charges ground referred C2 with this information. The LTC1052 measures the voltage across C2 and provides the circuit's output. Gain is set by the ratio of the amplifier's feedback resistors. Normally, the LTC1052's output stage can swing within 15 mV of ground. If operation all the way to zero is required, the circuit shown in dashed lines can be employed. This conftgu-ration uses the remaining LTC1043 section to generate a small negative voltage by inverting the diode drop. This potential drives the 10-KΩ, pull-down resistor, forcing the LTC1052's output into class A oper-ation for voltages near zero. Note that the circuit's switched-capacitor front-end forms a sampled-data filter allowing the common-mode rejection ratio to remain high, even with increasing frequency. The 0.0047μF unit sets front-end switching frequency at a few hundred Hz.



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