A BiFET automatic gain control amplifier for hearing aids

This paper describes an audio band automatic gain control (AGC) amplifier implemented in Bipolar/JFET(Vp=0.3 V) technology and is targeted for high performance hearing aid applications. A unique AGC topology was used where the AGC function is split into feedback and feedforward sections. The amplifier provides variable compression ratios from 1:1 to 4:1 compression, 4 pole bandsplit filter, and dualtime constant average signal detection. The single IC consumes only 0.3 mW from a 1 V supply.