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A switched-capacitor (SC) third-order single-loop single-bit delta-sigma analog-to-digital converter (ADC) for sensor interface is presented. The ADC is integrated on the same chip with a bandgap reference. To reduce the power consumption, opamp bias current switching technique is adopted. The prototype delta-sigma ADC fabricated in a 0.18μm CMOS process achieves 89.2 dB dynamic range (DR), 77.1 dB signal-to-noise ratio (SNR) and 77.0 dB signal-to-noise and distortion ratio (SNDR) over 10 kHz signal bandwidth with an over-sampling-ratio (OSR) of 128. The total power consumption is 1.42 mW at 1.8 V supply.

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A third-order single-bit delta-sigma modulator is presented in this paper. An op-amp dynamic current biasing technique is used to improve the power-efficiency of the modulator. The voltage reference block is integrated with the delta-sigma modulator core to avoid the use of large off-chip bypass capacitors and to minimize pin numbers. It achieves 89.2 dB dynamic range over 10 kHz signal bandwidth with an oversampling ratio of 128. The delta-sigma modulator core and on-chip voltage reference block consume 880 µW and 550 µW, respectively, from a 1.8 V power supply. The prototype chip occupies 1.26 mm 2 using a 0.18 µm CMOS technology.

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