Schmitt Trigger Thresholds Calculator

About this calculator

A Schmitt trigger is a comparator circuit with built-in hysteresis — it switches output states at a different input voltage going up than coming down, which prevents a noisy or slowly-changing input signal from triggering multiple false transitions. For the classic non-inverting op-amp version, the upper and lower thresholds are VT = ±(R1/R2)·Vsat, where Vsat is the op-amp's output saturation voltage and R1/R2 sets the feedback ratio; the gap between the two thresholds is the hysteresis band.

Analog and digital design engineers use Schmitt triggers to clean up slow or noisy signals — squaring up a sine wave into a clean digital pulse, debouncing a mechanical switch, or building reliable oscillators — and calculating the exact thresholds up front is essential for setting the right noise margin for a given application.