> Replace This Line with Your Paper Identification Number (double-click Here to Edit) < 1 a Biomimetic, 4.5µw, 120+db, Log-domain Cochlea Channel with Agc

This paper deals with the design and performance evaluation of a new analogue 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 – analogue 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 4-order OZGF channel (equivalent to an 8-order cascaded filter structure) through both detailed simulations and measurements from a fabricated chip using the commercially available 0.35μm AMS CMOS process. The whole system is tuned at 3kHz, dissipates a mere 4.46μW of static power, accommodates 124dB (at <5% THD) of input dynamic range at the center frequency and is set to provide up to 70dB of amplification for small signals.

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