Schmitt triggers
Many logic elements require fast edges to operate correctly. Edges can be degraded for a variety of reasons; stray capacitance or a non digital device for example. The Schmitt trigger always gives fast edges on its output signals regardless of the edge speed of the input signals. The transfer function of a conventional gate is shown on Figure 1(a).The transfer function of a Schmitt trigger incorporates hysteresis and is shown on Figure 1(b).
Figure 1(d ) shows a slow changing input and the resulting output, which always has fast clean edges.
A Schmitt trigger has the conventional logic symbol with an added hysteresis loop similar to Figure 1(c). Schmitt triggers are usually available in hex inverter or quad two input gate ICs. The 74123, for example, is a popular quad two input Schmitt trigger NAND gate.
Figure 1 The Schmitt trigger: (a) operation of a conventional inverter; (b) operation of an inverter with hysteresis; (c) logic symbol; (d) use of a Schmitt trigger to convert a slowly changing signal to a crisp digital signal.
Exemple of Schmitt trigger :
CD40106 CD40106BE 40106 HEX SCHMITT TRIGGER IC / Integrated Circuit
you can buy this Schmitt trigger on amazon
