VERDI: an acoustically programmable and adjustable CMOS mixed-mode signal processor for hearing aid applications

• Published in: IEEE journal of solid-state circuits Vol. 31; no. 5; pp. 634 - 645
• Main Authors: Duque-Carrillo, J.F., Malcovati, P., Maloberti, F., Perez-Aloe, R., Reyes, A.H., Sanchez-Sinencio, E., Torelli, G., Valverde, J.M.
• Format: Journal Article
• Language: English
• Published: IEEE 01-05-1996
• Subjects: Auditory system; Circuits; CMOS process; Decoding; Filters; Frequency response; Gain control; Preamplifiers; Pressure control; Signal processing
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/4.509846

A CMOS mixed-mode fully-differential signal processor (VERDI), that constitutes the core of a hearing aid system, is introduced. Its characteristics (frequency response, compression level, and output sound pressure level) are wireless controlled by means of dual tone multi-frequency (DTMF) encoded signals transmitted by an external unit. A system description is provided, and the implementation and experimental results of the key components (preamplifier, antialiasing filter, automatic gain control, filter section, output amplifier, and DTMF receiver/decoder) are covered in more detail. The circuit has been fabricated in a conventional 1.2 /spl mu/m CMOS n-well process and operates from a single 1.3 V battery, although a dc/dc converter is required. It consumes typically less than 1 mA and occupies 28 mm/sup 2/ of silicon. The dynamic range is larger than 66 dB for the maximum input signal (54 mV/sub rms/=108 dB SPL).