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A 0.2-mW CMOS ΣΔ modulator for speech coding with 80 dB dynamic range

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2 Author(s)
E. J. vanderZwan ; Philips Res. Lab., Eindhoven, Netherlands ; E. C. Dijkmans

A CMOS ΣΔ modulator for speech coding with continuous-time loopfilter is presented. Compared to switched-capacitor implementations, the relaxed bandwidth requirements of the active elements of the loopfilter reduce the power consumption. Furthermore, the need for an antialiasing filter at the modulator input is eliminated. A fourth-order, 64× oversampling ΣΔ modulator for application in portable telephones was designed and shows 80 dB dynamic range over the 300-3400 Hz voice bandwidth. Its input is directly connected to the microphone (maximum 40 mVRMS). Total harmonic distortion (THD) is below -70 dB at 95 μA current consumption from a 2.2 V supply voltage. The active die area of the modulator is 0.5 mm2 in a standard 0.5-μm CMOS process

Published in:

IEEE Journal of Solid-State Circuits  (Volume:31 ,  Issue: 12 )