Design of ternary Schmitt triggers based on its sequential characteristics

By analyzing the working characteristics of binary Schmitt circuits we find their sequential characteristics, which makes us follow the method of sequential circuits to design Schmitt circuits. The sequential design technique is extended to the study of ternary Schmitt circuits in this paper. The designed ternary Schmitt trigger has a similar structure with a ternary flip-flop. PSPICE simulation with TTL technology shows that the circuit has correct Schmitt characteristics.

1. Sequential characteristic analysis of Schmitt circuits

In the traditional binary digital circuits, Schmitt circuit is a useful device. One of its important characteristics is that it has different thresholds for the positive-going and negative-going direct current (DC) transmission characteristics, and the difference between them is called hysteresis. Such a trigger scheme makes it capable of receiving slowly varying input signals and effectively suppressing the interference imposed on the input signal. In digital circuits, Schmitt circuit is used as an effective device to reshape input signals. Obviously, in the multiple-valued logic, multiple-valued Schmitt trigger should hold its corresponding position and usage as its binary counterpart. Studying multiple-valued Schmitt circuits is helpful for the completeness of the multiple valued logic study.