Characterization of operational amplifiers subject to signals at frequencies far above their passband

摘要

Electromagnetic phenomena con seriously interfere with remote measuring systems. An operational amplifier integrated circuit with an operating frequency range located at a few MHz can be perturbed by high-frequency sources such as those emanatingfrom mobile telephone systems. This article discusses a study into a BiFET operational amplifier having again-band product of 6 MHz. Over the frequency range covered by the study, we find two types of phenomenon, involving detection and transfer of thehigh-frequency disturbance through the component. The first phenomenon is observed at interfering frequencies below 700 MHz and the second at frequencies above 700 MHz. We analyse experimental results and offer theoretical interpretations.