Low-voltage, current-mode trigger circuits and relaxation oscillators

This thesis presents an overview of the design methodology and analysis of low-voltage current-mode monolithic trigger circuits and relaxation oscillators in CMOS circuit design. Trigger circuits (window comparators and Schmitt triggers) are mainly used in sensor interfacing circuits to reduce the sensitivity to noise and disturbance. The Schmitt trigger is also an important component used in relaxation oscillators (muitivibrators). Multivibrators are one type of controlled oscillators that are widely used in communication circuits and analog-to-frequency converters. Because of the demand for lower fabrication cost and higher system portability, the trend is for CMOS analog circuit design to increasingly shift toward "systems on a chip" with lower supply voltages in order to take advantage of digital signal processing techniques. However, it is challenging to design high-performance analog periphery circuits at low supply voltages. Current-mode circuits are suitable for systems requiring low supply voltages, because of the simplicity of their structures that are based on current mirrors and require no high performance amplifiers. Hence, the design approach of utilizing current-mode circuits is selected in this thesis.;Using CMOS circuit design, the basic building blocks of trigger circuits and multivibrators are investigated. These include bias circuits, current mirrors, current switches and digital latches. Several low-voltage current-mode window comparators and Schmitt triggers with fully adjustable trigger levels are designed with the input current that is bi-directional. The width of the trigger levels can be adjusted independent of the supply voltages and the location of the trigger levels can be shifted along the input axis. Simulation in a 2-...