A 134-μW 99.4-dB SNDR Audio Continuous-Time Delta-Sigma Modulator With Chopped Negative-R and Tri-Level FIR-DAC

Abstract

This article presents a low-power audio continuous-time delta-sigma modulator (CTDSM) that employs a chopped negative-R and a tri-level finite impulse-response (FIR) DAC. The noise of the first opamp is mitigated by using a negative-R at the virtual ground of the first integrator, and the negative-R is then chopped to remove the intrinsic <inline-formula> <tex-math notation= LaTeX >${1/f}$ </tex-math></inline-formula> noise of the negative-R. The highly linear feedback DAC is realized with a 6-tap tri-level FIR-DAC whose inter-symbol interference (ISI) is kept less than −120 dB. The CTDSM fabricated in 65-nm CMOS technology occupies an active area of 0.28 mm². It achieves 99.4-dB SNDR, 101-dB SNR, 102.8-dB dynamic range (DR), and 110.2-dB SFDR in a 24-kHz bandwidth, while consuming only <inline-formula> <tex-math notation= LaTeX >$134~\\mu \\text{W}$ </tex-math></inline-formula>. This corresponds to a state-of-the-art figure-of-merit (FoM) of 185.3 dB.