A Low Power Sigma-Delta Modulator Using Class-C Inverter

In switched capacitor sigma-delta (ΣΔ) analog-to-digital converters (ADCs), an operational transconductance amplifier (OTA) is the main building block and consumes most of power. This paper proposes that the OTAs can be replaced with class-C inverters for low-power consumption without sacrificing the performance. A second order ΣΔ modulator using class-C inverter technique is fabricated with a 0.35-μm CMOS process, occupies 3024 μm
²
, dissipates 5.6-μW under 1.2V supply-voltage, and provides 63-dB/72-dB/76-dB SNDR/SNR/DR over 8-kHz signal bandwidth.