Research And Design Of Instrumentation Amplifier With Low Power, High Accuracy And Wide Common Mode Input

With the rapid development of electronic technology, instrumentation amplifiers are being more and more widely used. Instrumentation amplifier is typically used in the occasion of amplifying a small differential signal in high common-mode voltage. General requirements for instrumentation amplifier are high accuracy, low gain error, high common-mode rejection ratio and low power consumption with battery-powered applications.This paper analyzes and studies the structure of several common instrumentation amplifier circuits and the indirect current-feedback architecture is the final choice. This instrumentation amplifier circuit contains only input differential voltage and the first stage can provide all the common-mode rejection while the second grade can provide all the differential gain and further suppress common mode signal. This instrumentation amplifier with low power consumption, high accuracy and wide common mode input range mainly includes power-on reset, bandgap, charge pump, instrumentation amplifier core and gain error calibration modules. Instrumentation amplifier core circuit with differential structure can reduce outside noise interference and achieve rail-to-rail input and output with no common mode crossover distortion at the same time. The introduced self-calibration technology can further improve the accuracy of the instrumentation amplifier. The chip uses0.35um CMOS mixing process to do physical implementation and the chip area is1.2cm x1.24cm. The simulation test results show that the circuit realizes the self-calibration function and the attainable calibrated input offset voltage can reach±22mV. The gain error of instrumentation amplifier is10μV,-3dB bandwidth is450kHz, the common mode rejection ratio is-136dB, low-frequency equivalent input noise voltage approximately reaches570μVp-p and power consumption is about1.4mA. All the results indicated that the design meets the original system design performance requirements.