Hysteresis and Margins

Falling Threshold Switches Low

the lower boundary changes state

The same Schmitt input uses the lower threshold to leave a prior HIGH state. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Inside the band, the prior state holds

The middle input lies between the two thresholds, so prior HIGH stays HIGH.

2 V<52 V<3 V⇒hold prior2\ \text{V} < \tfrac{5}{2}\ \text{V} < 3\ \text{V}\Rightarrow \text{hold prior}
Hysteresis bandInside the band, the prior state holds.V5/2 VV2 VV3 VV5 V+-5/2 V+-2 V+-3 V+-5 Vprior HIGHHIGH

Dropping below the lower threshold switches LOW

The input is 1 volt, below the lower threshold of 2 volts.

1 V≤2 V⇒LOW1\ \text{V} \le 2\ \text{V}\Rightarrow \text{LOW}
Falling outputThe lower threshold makes the output LOW.V1 VV2 VV3 VV0 V+-1 V+-2 V+-3 V+-0 Vprior HIGHLOW