Subthreshold operation of Nauta's operational transconductance amplifier

This paper investigates the subthreshold operation of the inverter-based operational transconductance amplifier for the potential use in very low power data conversion systems. Circuit analysis and sizing strategies are presented, and a first order continuous-time delta-sigma modulator circuit is used as a case study to verify the performance of the amplifier when operating in subthreshold region. We demonstrate experimental results using a digitally configurable Nauta operational transconductance amplifier implemented in a 180nm CMOS process which shows up to 97.76 percent power reduction when 600mV is used instead of 1.8V as supply with better figure of merit and without significant signal-to-noise distortion ratio penalty highlighting its significant potential at subthreshold operation.