Low-voltage CMOS subthreshold log amplification and AGC

A new very-low-voltage CMOS circuit strategy is presented for amplifying and AGC stages. Voltage supply scaling is optimised through the combination of log companding and the MOSFET operating in subthreshold. Based on this idea, a complete set of CMOS basic building blocks is proposed for programmable amplifiers and AGC circuits. Simulated and experimental results are reported at IV supply to demonstrate the validity of the proposed techniques for the design of low-voltage audio systems-on-chip, such as hearing aids.