Analysis of EM noise suppression techniques for operational amplifier based design

摘要

Operational Amplifier (OPAMP) is an integral part of many hardware board design. When used in conjunction with a sensor, the main purpose of this is to amplify the small signal from the sensing element and before being fed to ADC for further processing. The functionality demands high differential gain. Any mismatch in physical dimension of the input traces makes the board highly sensitive to external noise like electromagnetic (EM) coupling from any nearby device as the differential noise get amplified by the OPAMP and can be falsely detected as a signal at the processor. In this paper mechanism in which Radiated Field can enter the OPAMP and get demodulated and enter the ADC stage of microcontroller giving a false trigger is discussed. Control mechanism such as using guard traces for minimizing differential voltage across OPAMP and filtering the RF feedback to the input to make the design more robust against unwanted RF are discussed.