A Biomimetic, 4.5 µW, 120+dB, Log-domain Cochlea Channel with AGC
Venue
IEEE JSSC (Journal of Solid-State Circuits), vol. 44 (2009), pp. 1006-1022
Publication Year
2009
Authors
Andreas G. Katsiamis, Emmanuel M. Drakakis, Richard F. Lyon
BibTeX
Abstract
This paper deals with the design and performance evaluation of a new analog CMOS
cochlea channel of increased biorealism. The design implements a recently proposed
transfer function, namely the One-Zero Gammatone filter (or OZGF), which provides a
robust foundation for modeling a variety of auditory data such as realistic
passband asymmetry, linear low-frequency tail and level-dependent gain. Moreover,
the OZGF is attractive because it can be implemented efficiently in any
technological medium-analog or digital-using standard building blocks. The channel
was synthesized using novel, low-power, class-AB, log-domain, biquadratic filters
employing MOS transistors operating in their weak inversion regime. Furthermore,
the paper details the design of a new low-power automatic gain control circuit that
adapts the gain of the channel according to the input signal strength, thereby
extending significantly its input dynamic range. We evaluate the performance of a
fourth-order OZGF channel (equivalent to an 8th-order cascaded filter structure)
through both detailed simulations and measurements from a fabricated chip using the
commercially available 0.35 mum AMS CMOS process. The whole system is tuned at 3
kHz, dissipates a mere 4.46 µW of static power, accommodates 124 dB (at < 5%
THD) of input dynamic range at the center frequency and is set to provide up to 70
dB of amplification for small signals.
