In this work a novel CMOS Miller operational amplifier with high immunity to EMI is presented. The proposed CMOS Miller OpAmp uses the replica concept with the source-buffered technique in order to achieve a higher EMI immunity over a wide range of frequencies, from 10MHz to 1GHz. Measured 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 (10MHz to 1GHz), when a 900mVpp EMI signal is injected into the non-inverting input and when the OpAmp is connected in a voltage-follower configuration. In contrast, the classic Miller OpAmp generates a maximum output offset voltage of 215mV, the modified replica Miller OpAmp generates a maximum output offset voltage of 90mV and the source-buffered Miller OpAmp generates a maximum output offset voltage of 22mV at 1GHz, under the same operating conditions.