Analysis of a Low Power Inverting CMOS Schmitt Trigger Operating in Weak Inversion

Abstract

This article analyzes the operation of a low power inverting CMOS Schmitt trigger in weak inversion. The analysis is based on an earlier proposed analytical model, which relates the hysteresis voltages to the transistors' dimensions, the supply voltage, and the temperature. The maximum error between the analytical and simulated transition voltages is below 10%, relative to the supply voltage. By optimizing the device sizes, the error reduces to 4%. The operation of the Schmitt trigger in weak inversion is also experimentally validated through an ASIC fabricated in AMS 0.35μm CMOS process. The maximum error between the modeled and measured transition voltages is below 7%. Furthermore, the power consumption as a function of the supply voltage is analyzed. Overall, the proposed model may be used to optimize the operation of the analyzed Schmitt trigger circuit for low power operation.