This paper presents a novel low-noise and high-precision readout circuit for tunnelling magnetoresistive (TMR) array to evaluate the suitability of biomagnetic measurement platform for detection of weak biomagnetic fields. We propose a three operational-amplifier architecture with a high input impedance and an adjustable gain for the fabricated TMR sensor that is highly miniaturized and can be operated at room temperature. Designed in a standard 0.18 µm CMOS process, the simulation results show that the proposed system achieves good performances in terms of gain, linearity, power, and noise by employing a chopper stabilization technique and common mode feedback.