Adaptive Signal to Noise Ratio Scalable Analog Front-End Continuous Time Sigma Delta Converter For Digital Hearing Aids by

i ABSTRACT A dual-channel directional digital hearing aid (DHA) front end using Micro Electro Mechanical System (MEMS) microphones and an adaptive-power analog processing signal chain is presented. The analog front end consists of a double differential amplifier (DDA) based capacitance to voltage conversion circuit, 40dB variable gain amplifier (VGA) and a continuous time sigma delta analog to digital converter (CT-Σ∆ ADC). Adaptive power scaling of the 4th order CT-Σ∆ achieves 68dB SNR at 120µW, which can be scaled down to 61dB SNR at 67µW. This power saving will increse the battery life of the DHA. ii DEDICATION I dedicate this dissertation to my family, especially my mother and father for their infinite support and sacrifice. To my wife for inspiring me.