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 the typical hysteresis width for LM393?
For most applications, 100mV to 1V hysteresis is sufficient. Battery monitoring typically uses 200-500mV. Very small hysteresis (<50mV) may not prevent oscillation; very 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 with open-collector or push-pull output. LM358 has slightly slower response time but works identically. LM339 is just two LM393 in one package (4 channels).
What if my LM393 is out of stock?
The new LM393B is a drop-in replacement with better specs (38V max, 2kV ESD, 0.37mV offset). TI, ON Semi, STMicroelectronics, and Diodes Inc all make compatible parts. Use our IC Selector tool to compare alternatives.