LM393 Hysteresis Calculator
Calculate upper and lower threshold voltages (VT+, VT-) and hysteresis width for LM393 comparator circuits. Includes interactive waveform visualization, ASCII circuit diagram, and standard E96 resistor recommendations.
⚙️ Circuit Parameters
Enter parameters and click Calculate to see results
Vcc (5V)
│
├── R1 ──┐
│ │
V_ref ─┤ ├── INPUT+ (LM393 Pin 3)
│ │
├── R3 ──┤
│ │
GND R2
│
├── INPUT- (LM393 Pin 2)
│
OUTPUT (LM393 Pin 1)What is Hysteresis in LM393 Comparators?
Hysteresis is a technique used in comparator circuits to prevent output oscillation when the input signal is near the threshold voltage. Without hysteresis, even small noise on the input can cause the LM393 output to rapidly switch between high and low states - a problem known as "chattering".
By adding positive feedback through a resistor (R2 in our calculator), the threshold voltage becomes dependent on the current output state. This creates two distinct thresholds: VT+ (when output switches from LOW to HIGH) and VT- (when output switches from HIGH to LOW).
When to Use LM393 Hysteresis
- Battery voltage monitoring (BMS) - prevent rapid cycling at threshold
- Light/dark sensor circuits - avoid flicker at ambient level
- Sound detection modules - reject background noise spikes
- Motor speed sensors - clean tachometer signals
- Temperature controllers - stable switching behavior
LM393 vs LM358 vs LM339
The LM393 is a dedicated dual voltage comparator. The LM358 is a dual op-amp that can be used as a comparator (slower but cheaper). The LM339 is a quad comparator. For most hysteresis applications, LM393 is the standard choice.
FAQ
What is hysteresis in an LM393 comparator?
Hysteresis is a technique that adds two distinct threshold voltages (V_threshold_high and V_threshold_low) to prevent output oscillation when the input signal is near the threshold. The gap between these thresholds (hysteresis width) ensures clean switching.
How do I choose the right hysteresis width?
For battery monitoring, 200-500mV is typical. For light sensors, 100-300mV. For audio detection, 50-200mV. Too small (<50mV) may not prevent oscillation; too large (>2V) makes the circuit insensitive to small signal changes.
Can I use this calculator for LM358 or LM339?
Yes. The hysteresis formulas apply to any comparator IC. LM358 is a dual op-amp usable as a comparator (slower but cheaper). LM339 is a quad comparator (4 channels in one package).