A 91.7dB-SNDR 5kHz BW 18.5μW PPD-based Single-OTA Zoom ADC using CLS-enhanced Inverter Amplifier

This paper presents a pseudo-pseudo-differential (PPD)--based single-OTA 2nd-order zoom ADC, which employs a 4-bit SAR conversion followed by a 2 nd-order $\Delta \Sigma$ modulator using a single-OTA. The PPD technique significantly minimizes the OTA noise at low frequencies. A CLS-enhanced cascode inverter is proposed as the OTA, boosting its DC gain to 75dB to meet structural requirements. The chip, designed in a 55nm CMOS process with a 1V supply, achieves a 91.7dB SNDR while consuming $18.5 \mu \mathrm{~W}$ at a signal bandwidth 0 f 5 kHz, resulting in a Schreier figure-of-merit (FoM) of 176.0 dB.