- A Schmitt trigger is a comparator with built-in hysteresis that uses two switching thresholds (V_TH and V_TL) to eliminate noise and ensure stable output transitions.
- Inverting op-amp Schmitt trigger thresholds: V_TH = (R1/(R1+R2)) × V(sat), V_TL = (R1/(R1+R2)) × (-V(sat)), hysteresis width V_H = (2×R1/(R1+R2)) × |V(sat)|.
- Non-inverting op-amp Schmitt trigger thresholds: V_UT = +(R1/Rf) × V(sat), V_LT = -(R1/Rf) × V(sat), hysteresis = 2×(R1/Rf)×|V(sat)|.
- Discrete BJT Schmitt trigger uses two transistors with common emitter resistor; hysteresis arises from emitter voltage shift, typically ~0.4 V.