DESIGN OF ULTRA LOW VOLTAGE LOW NOISE ANALOG FRONT END FOR BIO-POTENTIAL SIGNALS

Abstract

The information extracted from the bio-potential signals such as ECG, EEG, ECoG, ERG and ENG is extensively used for health care and medical treatment purposes. The use of bio-potential acquisition systems is not only limited to the hospitals but also extended to the homes for ubiquitous health care. Therefor the demand of portable bio-signal measurement system is increasing. The key constituent to this kind of systems is the analog front-end (AFE). The analog readout front-end extracts the bio-signals directly from human body through electrodes and defines the extracted signal quality. The most critical block in an bio-potential acquisition system is the AFE as it is connected directly to the human body and the output this should be ready to feed the subsequent stages that are ADCs and DSPs. This block must operate under low power consumption with minimal added noise to ensure the better signal quality with enhanced battery life, when incorporated in portable bio-signal acquisition systems. In this dissertation a novel multi-function Analog Front-End is proposed. This analog readout front end is oriented to be employed in flexible and portable bio-potential signal acquisition systems. The essential contribution of this work is the new Forward Body Biased Current Mode Amplifier (FBBCMA) based on convention forward body biased technique for low-voltage operation. The proposed FBBCMA achieves very low noise performance because of inherent properties of current mode topology. Forward body biasing of MOS devices further reduces the flicker noise that is a critical concern in circuits operating at low frequencies. Low power consumption and other advantages are achieved by the aid of the forward body biasing and current mode topology. A complete analog readout front end is implemented and simulated using the standard TSMC 180nm parameters and P-Spice as simulator. This AFE consist of a pre amplifier followed by a band pass filter to enhance in band signals and reject the signals that are laying out of the band of interest. Tuneable bandwidth of AFE enables it to serve as the first stage in variety of bio-signal acquisition systems. The simulation results show that the designed circuits meet the basic requirements of the low power consumption under low noise operation for long time portable bio-potential recorders.