Very Low Power Sigma Delta Modulator for Biomedical Applications

This paper discusses the design of picowatt power Sigma-delta modulator with genetic algorithm (GA) based oversampling technology. This Sigma-delta modulator design is paid special attention to its low power application of portable electronic system in digitizing biomedical signals such as Electro-cardiogram (ECG), Electroencephalogram (EEG) etc. [1]. A high performance, low power second order Sigma-delta modulator is more useful in analog signal acquisition system. Using Sigma-delta modulator can reduce the power consumption and cost in the whole system. The original biomedical signal can be reconstructed by simply applying the digital bit stream from the modulator output through a low-pass filter. The loop filter of this modulator has been implemented by using switch capacitor (SC) integrators and using simple circuitry consists of OpAmps, Comparator and DAC. In general, the resolution of modulator is about 12-16 bits for biomedical application. In this second order Sigma-delta modulator simulation results of shows a 68 dB signal-to-noise-and distortion ratio (SNDR) in 200 Hz biomedical signal bandwidth and a sampling frequency equal to 1MHz in the 0.18 μ CMOS technology. The power consumption is 1.45 pw. It is very suitable for low power application of biomedical instrument design.