Abstract: This paper presents a third-order single-loop delta-sigma modulator of a biomedical micro-system for portable electroencephalogram (EEG) monitoring applications. To reduce the power consumption, the loop filter of the proposed modulator is implemented by applying a switched-capacitor structure. The modulator is designed in a 0.35-μm 2P4M standard CMOS process, with an active area of 365 × 290 μm². Experimental results show that this modulator achieves a 68 dB dynamic range with an input sinusoidal signal of 100 Hz signal bandwidth under a 64 over-sampling ratio. The whole circuit consumes 515 μW under a 2.5 V power supply, which is suitable for portable EEG monitoring.

Key words: analog-to-digital converter