Comparator hysteresis
Comparator hysteresis with circuit equations and operating-limit checks.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Inverting thresholds: VTH,TL = (Vref/Rref + Vout/Rh)/(1/Rref+1/Rh)
Non-inverting thresholds: Vin,threshold = Vref(1+Rin/Rh) - Vout Rin/Rh
Loaded open-drain high: (Vsupply-VOH)/Rpullup = Iexternal + (VOH-Vfeedback-node)/Rh
Assumptions
- Use a comparator specified for the required input/output behaviour. Inverting mode mixes reference and output at V+ and applies signal to V-. Non-inverting mode mixes signal and output at V+ and applies reference to V-.
- Open-drain synthesis solves the high-state pull-up and feedback loading simultaneously at the switching threshold. The external high-state load is constant current. VOL is user-specified; the computed low-state sink current must be checked against the comparator data sheet. Window mode uses two independent threshold comparators.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Configuration
- inverting
- Desired upper threshold
- 3 V
- Desired lower threshold
- 2 V
- Push-pull output high
- 5 V
- Output low level
- 0 V
- Input/reference resistor
- 10000 Ω
- Output stage
- push-pull
- Open-drain pull-up
- 10000 Ω
- Pull-up supply
- 5 V
- High-state external load current
- 0 A
- Test input
- 2.5 V
Results
- Feedback resistor
- 40000 Ω
- Required reference
- 2.5 V
- Upper threshold
- 3 V
- Lower threshold
- 2 V
- Loaded high output
- 5 V
- State at test input
- History-dependent hysteresis band
- Low-state sink current
- 0 A