An oscillator-based CMOS magneto-sensitive biosensor with a low noise and low temperature coefficient LDO regulator

This paper presents a high sensitivity oscillator-based magneto-sensitive biosensor. A fully integrated on-chip low noise low-dropout voltage regulator (LDO) with a low temperature coefficient double-stacked diode bandgap is introduced to suppress the environmental variations, e.g. voltage vibration, temperature drift. As an implementation example, a biosensor cell is designed in a standard 180-nm CMOS process. An ultra low output noise of the LDO is achieved, i.e. 443 and 150nV/√Hz at 100Hz and 1kHz, respectively. The biosensor with the proposed LDO achieves an extra 6.1dB suppression of the frequency drift. The magnetic sensing capability of the presented biosensor is verified by avidin-labeled MNPs with diameters of 200nm, indicating a frequency shift of 0.03MHz from the 1μg/ml biotin-IgG sample.