10.2 A 139 µ W 104.8dB-DR 24kHz-BW CT ΔΣM with Chopped AC-Coupled OTA-Stacking and FIR DACs

Continuous-time delta-sigma modulators (CTΔΣMs) have inherent anti-aliasing, resistive inputs, and relaxed settling requirements making them popular for audio applications. Due to the relatively low bandwidth, the noise-efficiency of the first OTA has a substantial influence on the power and FoM. OTA-stacking is a recently reported technique that improves the noise-current tradeoff in continuous-time amplifiers [1], [2]. This is the central idea behind the proposed CTΔΣM where an AC-coupled stacked OTA improves the noise-efficiency of the first integrator. The ADC with a 3-stack OTA achieves 100.9dB SNDR and 104.8dB DR in a 24kHz bandwidth while consuming 139μW for a state-of-the-art Schreier FoM
_DR
of 187.2dB.