Relaxation Oscillator Exploiting PTAT Hysteresis of Differential Schmitt Trigger

Abstract

In this paper, we proposed a novel relaxation oscillator to address the frequency variation caused by the comparator delay. The conventional operational transconductance amplifiers (OTAs)-comparator is replaced with a Schmitt trigger to significantly reduce the delay. This Schmitt trigger is implemented by a differential structure operating in the subthreshold region to generate a proportional to absolute temperature (PTAT) hysteresis. Both the voltage reference and the current source are made PTAT as well. The proposed oscillator can be made ultra-low power and have excellent frequency stability over process, voltage and temperature (PVT) variation.