Dynamic-range analysis and maximization of micropower G[subscript m]-C bandpass filters by adaptive biasing

Abstract

We analyze and present an input gain-varying scheme for maximizing dynamic range in a well-known G[subscript m]-C bandpass filter by both minimizing noise for small input signals, and by achieving balanced swing levels at all filter nodes for large input signals. A micropower bandpass filter suitable for use in cochlear implants and other power-constrained biomedical applications was implemented and tested in subthreshold CMOS. At a center frequency of 1.4 kHz and quality factor of 4, the filter has 70 dB of dynamic range (57 dB maximum SNR, 2.5% total harmonic distortion (THD)) and consumes 2.55 muW of power.