LAUSR

A closed-loop high-precision front-end interface circuit in a standard 0.35 [Formula: see text]m CMOS technology for a tunneling magneto-resistance (TMR) sensor is presented in this paper. In consideration of processing a low frequency and weak geomagnetic signal, a low-noise front-end detection circuit is proposed with chopper technique to eliminate the 1/f noise and offset of operational amplifier. A novel ripple suppression loop is proposed for eliminating the ripple in a tunneling magneto-resistance sensor interface circuit. Even harmonics is eliminated by fully differential structure. The interface is fabricated in a standard 0.35 [Formula: see text]m CMOS process and the active circuit area is about [Formula: see text]. The interface chip consumes 7 mW at a 5 V supply and the 1/f noise corner frequency is lower than 1 Hz. The interface circuit of TMR sensors can achieve a better noise level of [Formula: see text]. The ripple can be suppressed to less than 10 [Formula: see text]V by ripple suppression loop.