A 0.8-V 230-μW 98-dB DR Inverter-Based ΣΔ Modulator for Audio Applications

This paper presents a Sigma Delta modulator based on a gain-boost class-C inverter for audio applications. The gain-boost class-C inverter behaves as a low-voltage subthreshold amplifier and boosts its dc gain for the high-precision requirement. Meanwhile, an on-chip body bias is used to compensate the performance degradation of the inverter at a slow process corner or low supply voltage. The proposed inverter-based modulator is fabricated in a 65-nm mixed-signal CMOS process with a die area of 0.3 mm(2). The experimental chip achieves 91-dB peak signal-to-noise-plus-distortion ratio (SNDR), 94-dB signal-to-noise ratio (SNR) and 98-dB dynamic range (DR) over a 20-KHz audio band with a 5-MHz sampling frequency and a 0.8-V supply voltage consuming only 230-mu W power, which demonstrates that the gain-boost class-C inverter is particularly suitable for low-voltage micro-power high-resolution applications.