A 1.95-V, 0.34-mW, 12-b sigma-delta modulator stabilized by local feedback loops

Abstract

The design of a low-power, low-voltage, 12-b 8-kHz bandwidth /spl Sigma//spl Delta/ modulator for high-quality voice that consumes only 0.34 mW at 1.95 V supply is described. The modulator employs a special architecture in which a third-order modulator is stabilized by a local feedback loop around each integrator. Unlike multistage /spl Sigma//spl Delta/ modulators, this architecture is very tolerant to the modest dc gain of low voltage op-amps. The architecture, together with special circuit techniques, permits a low-voltage switched capacitor implementation at 1.95 V-3.3 V supply using standard 1.2-/spl mu/m CMOS technology.