A highly EMI-immune folded cascode OpAmp in 0.18 μm CMOS technology

peer reviewed ; This paper describes a folded cascode CMOS instrumentation amplifier input stage, which has an increased immunity to electromagnetic interference (EMI). The proposed structure uses a source-buffered concept with a replica circuit to achieve a higher EMI immunity over a wide range of frequencies, from 10 MHz to 1 GHz. Circuit simulations illustrate how the proposed folded cascode amplifier reduces susceptibility to EMI even in the presence of large amplitude interferences. Simulation results show that the maximum EMI-induced output offset voltage for the proposed folded cascode amplifier is less than 8 mV over a wide range of frequencies (10 MHz to 1 GHz), when a 3.3 Vpp EMI signal is injected into the non-inverting input; when the amplifier is connected in a voltage-follower configuration. In contrast, the classic folded cascode amplifier generates a maximum input offset voltage of 700 mV at 1 GHz under the same operating conditions. © 2016 IEEE.