An 80-dB SNR 4th-order discrete-time sigma-delta modulator

This paper presents a 4th-order single-bit DT ΔΣ modulator for audio applications. To achieve higher signal-to-noise ratio (SNR), the compensation capacitors in the input of a comparator are exploited to reduce the metastability of a comparator. The proposed modulator has been fabricated in a quantizer level 0.18-μm CMOS process. Measurements show a SNR of 80.27 dB and a signal-to-noise and distortion ratio (SNDR) of 77.58 dB over a 40-kHz signal bandwidth with a sampling clock frequency of 10.24 MHz. A total power consumption including a clock generator is 340 μW with a 1.8-V supply voltage.