Comparator with Hysteresis

Comparator with Hysteresis

1. Noise reduction

   • An input line with hysteresis uses two switching levels Vhigh and Vlow. When the input voltage exceeds Vhigh, the output switches to a high level.
     • Only when the input voltage falls below Vlow (which should be lower than Vhigh), the output switches back to its low state.
       • The effect of an hysteresis can be seen in the next picture.

2. Comparator circuit

3. Effects of input noise on comparator operation

   • In many practical situations, noise (unwanted voltage fluctuations) appears (superimposed) on the input line --> we will have an erratic output voltage.
     • • When the sine wave approaches 0, the fluctuations due to noise may cause the total input to vary above and below 0 several times, thus producing an erratic output voltage as shown

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