Abstract

This research concerns the conception and the development of one specific circuit for a programmable hearing aid. In fact, actual hearing aid prosthesis should be flexible and programmable apparatus to the pathological case. First of all, it must be adjusted according to the pain threshold conserving all dynamics sound. Second, it must be adapted to different patient audiogram levels. In this article, we present the design of our conception using an adjustable amplifying chain formed by five analogue filters. In particular, such filters could be adjusted according to patient audiogram in order to compensate the considered hearing loss. Amplifier structure in this filters’ chain were independently controlled using current sources conceived by MOS transistors. At each amplifying structure, one could distinguish two stages referred as A_mg and A_mf : A_mg was conceived to control the filter’s gain where A_mf was conceived to control frequency band width. On the other hand, one MOS transistor current source was commanded by a Digital to Analogue Converter assuring then the possibility of programmability. The overall circuit was conceived using MOS technology in order to satisfy the low power incessant need for such biomedical applications.

Key words: Programmable hearing aid, Filter, Amplifier, Digital to Analogue Converter.