A true 1V CMOS log-domain analog hearing-aid-on-a-chip

This article proposes a novel design technique for very low-voltage (down to 1V) audio Systems-on-a-Chip based on the Log Companding theory and the MOSFET operating in subthreshold. A wide variety of CMOS basic building blocks for amplification, filtering, generation and modulation are given to implement low-frequency (up to 100KHz) applications. In particular, a complete programmable Hearing-Aid-on-a-Chip product is described as demonstrator of the proposed circuit technique.