Input filer prevents instrumentation-amp RF-rectification errors

摘要

INSTRUMENTATION AMPLIFIERS in a variety of applications that need to extract a weak differential signal from large common-mode noise or interference. However, designers often overlook the potential problem of RF rectification inside the instrumentation amplifier. The amplifier's common-mode rejection normally greatly reduces common-mode signals at an instrumentation amplifier's input. Unfortunately, RF rectification still occurs, because even the best instrumentation amplifiers have virtually no common-mode rejection at frequencies higher than 20 kHz.