This paper presents a fully integrated device for ECG acquisition on an MRI environment with on chip 3D HALL sensor for signal correction submitted in standard 0.35 μm CMOS technology. Based on a CMOS current conveyor (60 μA @ ± 1.65 V power supply, 100 MHz bandwidth and 10 GHz equivalent GBW circuit) the instrumentation amplifier used in this IC he circuit. The 3D Hall sensor features two vertical Hall devices (VHD) to measure component of the magnetic field oriented in the plane of the chip as well as one horizontal Hall device (HHD) to measure the component of the field orthogonally oriented to the plane of the chip. The 3D Hall sensor allows measuring the static field up to 1.5 T as well as the magnetic pulses of ± 20 mT generated during the MRI acquisition. The size of the complete design makes biological signal measurement in very hostile environment such MRI possible.