Ultra-Low-Power Biomedical Sensor Interface Front-End

Abstract

Abstract The front-end of biomedical sensors is a vital part in the acquisition of biopotential signals. The critical nature of such biopotential signals, imposes strict constrains on the design of the biomedical sensor front-end. The biopotential signals have a very low voltage amplitudes along with frequency band very close to DC. This requires a sensor interface front-end of high SNR. In addition, the signal acquisition process is battery powered, therefore the power consumption of the sensor front-end should be aggressively minimized. This thesis investigates the design challenges of the biomedical sensor frontend.

The processing of biopotential signals requires the employment of chopping stabilization technique, resulting in a front-end of low SC input impedance causing signal attenuation and measurement errors. Therefore, an input impedance boosting technique is proposed based on tunable negative capacitance circuit. Simulations show that the input impedance is boosted by factor of 500. Moreover, high amplitude output chopping ripples arises causing output voltage headroom reduction. Thus, a ripple suppression technique is proposed with the employment feed-forward loop for ripple filtration, while maintaining the biopotential signal. Simulations show a ripple attenuation of 68 dB.