A MEMS-Based Power-Scalable Hearing Aid Analog Front End

A dual-channel directional digital hearing aid front end using microelectromechanical-systems microphones, and an adaptive-power analog processing signal chain are presented. The analog front end consists of a double differential amplifier-based capacitance-to-voltage conversion circuit, 40-dB variable gain amplifier (VGA) and a power-scalable continuous time sigma delta analog-to-digital converter (ADC), with 68-dB signal-to-noise ratio dissipating 67 μ W from a 1.2-V supply. The MEMS microphones are fabricated using a standard surface micromachining technology. The VGA and power-scalable ADC are fabricated on a 0.25-μ m complementary metal-oxide semciconductor TSMC process.

I. Introduction

Hearing loss is one of the most common human impairments. It is estimated that by year 2015 more than 700 million people will suffer mild deafness [1]. Most can be helped by hearing aid devices depending on the severity of their hearing loss.