Design of current-mode CMOS multiple-valued schmitt triggers based on switch-signal theory

Guided by the switch-signal theory, the operations of current transmission switch used to describe the action of threshold-controllable switch in multiple-valued Schmitt trigger were established, and novel current-mode CMOS ternary and quaternary Schmitt triggers with output current and voltage signal were presented. The hysteresis current values of multiple-valued Schmitt triggers were controlled by only sizing the transistor aspect ratios. The main properties of the circuit are its simple structure, fully adjustable hysteresis and suitable for low-voltage applications. The designed circuits are simulated using HSPICE program and the model parameters of a TSMC 0.25 μm CMOS process, with 1.5V power supply. From the simulation results, the effectiveness of the proposed approach and the ideal characteristic of multiple-valued Schmitt circuit are validated.