Biasing technique for high dynamic range, low oversampling
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An accurate, continuous-time, active IC filter based on Gm-C integrators dedicated to the design of high dynamic range, low-oversampling ratio (OSR) continuous-time (CT) sigma-delta (ΣΔ) modulators is presented. Despite temperature and process variations, the biasing technique used enables design of a constant Gm-C cell without additional tuning circuit. A zero-IF (ZIF) receiver has been designed integrating I (in-phase) and Q (quadrature-phase) ΣΔ modulators. The measured peak SNR for a single modulator is 82.5 dB in temperature range [−30°C, +85°C]. Its power consumption, including I and Q modulators, biasing circuitry and delay-locked loop is 7.25 mW under 2.5 V.
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