Schmitt Trigger (Chip)

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Schmitt trigger devices are typically used in signal conditioning applications to remove noise from signals used in digital circuits, particularly mechanical contact bounce.

In EA a Schmitt trigger basically does this: If the input voltage is lower than 10V, the output is 0 (low), if the output is bigger or equal than 30V, the output will be 1 (high). For all voltages in between, the output value does not change. In other words the Schmitt trigger only changes from 1 (high) to low at the moment the input voltage is below 10V and it changes only from 0 (low) to 1 (high) if the voltage surpasses 30V.

You can see here a system where a Sinus-Signal with an amplitude of 50V is used as input to a NOT gate and another path where the signal is conditioned by a Schmitt trigger before going to the NOT gate.

If the Sinus is applied to the NOT gate directly, the output can start to oscillate as between 10V and 30V the signal is not defined as 0 or 1 and can be both. Using a Schmitt trigger eliminates the problems of these oscillations as the Schmitt trigger offers a defined output signal even in the case the input voltage is between 10V and 30V.

See also