Susceptibility of chopper OpAmps to EMI

This paper analyzes the effect of radio frequency interference (RFI) on the operation of high precision chopper operational amplifiers (chopper OpAmps), which are commonly used in sensor signal conditioning circuits. The rectification of RFI in continuous time differential input stages is discussed and the main outcomes of such analysis are used to explain the demodulation of RFI in chopper OpAmps. Finally, a new circuit topology based on chopped signals that shows high immunity to RFI is proposed.