Comparator Hysteresis Calculator Formula
Understand the math behind the comparator hysteresis calculator. Each variable explained with a worked example.
Formulas Used
Upper Trip Point
v_upper = v_ref + (v_supply - v_ref) * r2_kohm / (r1_kohm + r2_kohm)Lower Trip Point
v_lower = v_ref - v_ref * r2_kohm / (r1_kohm + r2_kohm)Hysteresis Band
hysteresis = v_supply * r2_kohm / (r1_kohm + r2_kohm)Variables
| Variable | Description | Default |
|---|---|---|
v_ref | Reference Voltage(V) | 2.5 |
v_supply | Output High Voltage(V) | 5 |
r1_kohm | R1 (to output)(kΩ) | 100 |
r2_kohm | R2 (to reference)(kΩ) | 10 |
How It Works
Comparator Hysteresis
Positive feedback adds hysteresis to prevent output chatter on noisy signals.
Formulas
V_upper = V_ref + (V_out_high - V_ref) x R2 / (R1 + R2)
V_lower = V_ref - V_ref x R2 / (R1 + R2)
Hysteresis = V_out_high x R2 / (R1 + R2)
Worked Example
Vref = 2.5 V, output swings to 5 V, R1 = 100k, R2 = 10k.
v_ref = 2.5v_supply = 5r1_kohm = 100r2_kohm = 10
- 01Upper = 2.5 + (5 - 2.5) x 10/110 = 2.5 + 0.227 = 2.727 V
- 02Lower = 2.5 - 2.5 x 10/110 = 2.5 - 0.227 = 2.273 V
- 03Hysteresis = 5 x 10/110 = 0.455 V
Ready to run the numbers?
Open Comparator Hysteresis Calculator