Fully Differential Difference Amplifier based Microphone Interface Circuit and an Adaptive Signal to Noise Ratio Analog Front end for Dual Channel Digital Hearing Aids

• Other Authors: Naqvi, Syed Roomi (Author)
• Format: Doctoral Thesis
• Language: English
• Published: 2011
• Subjects: Electrical Engineering; Biomedical Engineering; Adaptive Signal to Noise ratio; Continuous Time Sigma Delta; Digital Hearing Aids; Dual Channel; Feedback DAC; Fully Differential Difference Amplifier
• Online Access: http://hdl.handle.net/2286/R.I.9325

abstract: A dual-channel directional digital hearing aid (DHA) front-end using a fully differential difference amplifier (FDDA) based Microphone interface circuit (MIC) for a capacitive Micro Electro Mechanical Systems (MEMS) microphones and an adaptive-power analog font end (AFE) is presented. The Microphone interface circuit based on FDDA converts the capacitance variations into voltage signal, achieves a noise of 32 dB SPL (sound pressure level) and an SNR of 72 dB, additionally it also performs single to differential conversion allowing for fully differential analog signal chain. The analog front-end consists of 40dB VGA and a power scalable continuous time sigma delta ADC, with 68dB SNR dissipating 67u¬W from a 1.2V supply. The ADC implements a self calibrating feedback DAC, for calibrating the 2nd order non-linearity. The VGA and power scalable ADC is fabricated on 0.25 um CMOS TSMC process. The dual channels of the DHA are precisely matched and achieve about 0.5dB gain mismatch, resulting in greater than 5dB directivity index. This will enable a highly integrated and low power DHA === Dissertation/Thesis === Ph.D. Electrical Engineering 2011