A $63-\mu \mathrm{W}$ 92.68-dB SNDR Sigma-Delta Modulator using Self-biased Inverter-based Amplifiers

This paper presents an inverter-based sigma-delta modulator for use in wearable devices. This work employs the use of power-efficient integrators using self-biased, fully differential inverters, allowing for the amplifier to compensate any fluctuation due to process, voltage, and temperature (PVT) variations. To verify the effectiveness of the amplifier, a second-order discrete-time sigma-delta modulator is implemented in 0.18μm CMOS technology. The modulator achieves a 92.68 dB SNDR and 93.47 dB SNR while consuming 63-μW from a 1.8V supply, corresponding to a Walden's FOM of 89.96 fJ/step for a signal bandwidth of 10 kHz.