Design of A Novel Highly EMI-Immune CMOS Miller OpAmp Considering Channel Length Modulation

This paper presents a novel CMOS Miller operational amplifier (OpAmp) that has high immunity to electromagnetic interference (EMI). The proposed CMOS Miller OpAmp uses the replica concept with the source-buffered technique in order to achieve high EMI immunity across a wide range of frequencies (10 MHz to 1 GHz). The proposed amplifier is designed using the first-order quadratic mathematical model. The modeling includes the body effect and channel length modulation. The circuit has been fabricated using 0.18 µm mixed-mode CMOS technology. Measurement results illustrate how the proposed Miller OpAmp reduces susceptibility to EMI even in the presence of high-amplitude interferences that are as high as 1 Vpp. Experimental results show that the maximum EMI-induced output offset voltage for the proposed Miller OpAmp is less than 10 mV over a wide range of frequencies (10 MHz to 1 GHz) when a 900 mVpp EMI signal is injected into the noninverting input. In contrast, the classic Miller OpAmp generates a maximum output offset voltage of 215 mV at 1 GHz under the same operating conditions. The measured results of the EMI-induced input offset corroborates the circuit simulations.