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. Cl alternately 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.
Ultra-precision-instrumentation-amplifier - schematic

If operation all the way to zero is required, the circuit shown in dashed lines can be employed. This configuration uses the remaining LTC1043 section to generate a small negative voltage by inverting the diode drop. This potential drives the 10-KO, pull-down resistor, forcing the LTC1052"s output into class A operation 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 0.0047uF unit sets front-end switching frequency at a few hundred Hz.

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