Instruments offset due to RF EMI

One of the main error sources in instruments and sensors are electromagnetic interferences, EMI, acting on linear ICs at the detection and pre-conditioning stages. High frequency interferences with random amplitude cause a DC offset and a ripple due to noise amplitude modulation. This paper is devoted to study the effects of EMI on OPAMP offset. After several tests, a qualitative model for offset prediction is derived. A set of tests allows obtaining the model parameters, which depend on OPAMP type and circuit impedances. Such parameters allow the comparison of susceptibility between different OPAMP types. The model also allows the quantification of improvements when certain set up changes are introduced.