A Sensor Signal Amplifier Resilient to EMI

The rising level of electromagnetic pollution recorded in recent years represents a serious threat to the reliability of electronic devices and systems, which our life is plenty of. Besides corrupting nominal signals, electromagnetic interference (EMI) collected by interconnects can drive active nonlinear devices, which integrated circuits are made of, out of their nominal operating region and this usually results in distortion of the signals. The most harmful effect of such a process is the generation of the baseband intermodulation products, i.e., demodulated EMI that can be distinguished from nominal signals unlikely. This point is addressed in the first part of this paper where the expression of the offset induced by the radio frequency interference in MOS differential pair is derived then used to show the effect of EMI in feedback operational amplifiers. Some techniques to obtain higher immunity levels are also presented. The second part of this paper focuses on low-offset low-noise amplifiers of common use in sensor signal conditioning circuits that usually show high susceptibility to EMI. Aiming to address this issue, a new technique based on the dynamic cancelation of EMI-induced errors is presented, and evidences of its effectiveness are provided showing simulation and measurement results.