A tracking converter for resistive sensors based on a feedback active bridge

A so-called active bridge structure has been previously introduced as an alternative to the classical Wheatstone bridge structure combined with a low noise amplifier. It shows an advantage in terms of trade off between SNR and power consumption. The aim of this paper is to show the possibility of using the active bridge in a feedback structure that converts a relative variation of resistance into a digital word. This structure has been applied to a resistive spin-valve sensor with a nominal resistance of 750 Ω. The total power consumption is about 2 mA instead of 4.4 mA that would be consumed only by a Wheatstone bridge. A resolution of 12 bits is expected.