A 1.8V 204.8-$\mu \mathrm{W}$ 12-Bit Fourth Order Active Passive $\Sigma\Delta$ Modulator for Biomedical Applications

Abstract

This paper presents a 1.8V fourth-order 12.64 bits active-passive delta-sigma modulator. Passive integrators reduce power consumption which employs a switched capacitor circuit that operates from 1V to 1.8V supply voltage. The modulator is implemented in a $\mathbf{0.18}\mu \mathbf{m}$ CMOS process and achieves 77.85 dB SNR within 500 Hz at a sampling frequency of 256 kHz and consumes $\mathbf{204.8}\mu \mathbf{W}$ from a 1.8V supply. The Sigma-Delta modulator becomes the appropriate choice for high resolution as well as low frequency applications due to its highly linear property derived from a linear single-bit quantizer and oversampling technique.