What occurs at the output of a Schmitt trigger when the input signal exceeds the upper threshold?

When the input signal of a Schmitt trigger exceeds the upper threshold, the output transitions to a high state. This behavior is defined by the Schmitt trigger's fundamental operation, which includes hysteresis in its voltage thresholds.

In simpler terms, a Schmitt trigger is designed to provide a clean transition between two output states—high and low—when the input crosses specific voltage levels. Once the input surpasses the upper threshold, the output is driven high, creating a clear distinction that aids in eliminating noise and preventing false triggering from rapidly fluctuating input signals.

This output behavior is particularly useful in converting slowly changing inputs or noisy signals into a clean digital output, enhancing the reliability of signals in digital circuits. The other options either suggest no change or a change to a low state, which does not accurately reflect the designed functionality of a Schmitt trigger at the point where the input exceeds the upper threshold.