Design of a 1V subthreshold comparator for bio-medical over sampled ADCs

This paper presents a high speed and low supply voltage CMOS comparator which can be used in the design of a Sigma Delta Modulator for biomedical applications. The design of the comparator utilizes TSMC 180nm CMOS technology with a supply voltage of 1V. The comparator consists of a pre amplification stage, followed by a latch and a post amplification stage. A voltage reference circuitry with temperature coefficient of 171 ppm/°C is used to bias the comparator. The DC gain of the comparator is 113dB, with a unity gain frequency of 55 MHz. The power consumed is 76.6 μW and the comparator has an offset voltage of 2 mV. The layout area occupied by the design is 212 μm
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For an electro-oculogram (EOG) signal, the comparator can provide an Over Sampling Ratio (OSR) greater than 1000 which corresponds to a Signal to Noise Ratio (SNR) improvement greater than 90 dB.