Schmitt inverter

An inverter with built-in hysteresis logic (the input voltage at which it switches to a high output is guaranteed to be higher than the input voltage at which it switches to a low output). On a slow-rising or slow-falling input (such as in an Nv net), the Schmitt inverter ensures a very clean on / off transition. Note that a regular inverter, when it gets near its transition point, might switch on and off several times if there is any noise in the circuit (say from motors or other devices). A Schmitt device won't, because once it's on, the input voltage has to drop quite a bit before it can switch off. The schematic symbol for a Schmitt inverter is just that for a regular inverter, but with the addition of a hysteresis symbol:


Schmitt inverters are available for BEAM use in the 74*14 IC (where "*" is AC / ACT / HC / HCT). Schmitt inverters are named after their inventer, Dr. Otto Schmitt.

Wilf Rigter has written up a nice tutorial on building a Schmitt inverter from discrete (i.e., individual) transistors; it's hosted here.

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