Typical Schmitt trigger circuit diagram

Using a Schmitt trigger as an analog-to-digital converter, its output depends on the input signal size and has only two states. The voltage difference between the rising and falling switching times of the input voltage is called the hysteresis voltage Uhy. Its size can be changed by changing the threshold voltage of the left transistor, and is related to the size of the resistor Rv. If Rv=0 in this example, Uhy is approximately equal to 0.6V; if Rv=15k ohms, Uhy is approximately equal to 0.2V.