LM393Dual voltage comparator
Turn a voltage threshold into a clear digital decision.
LM393 contains two independent voltage comparators in an eight-pin IC. Each compares its positive and negative inputs and controls an open-collector output. When IN+ is below IN−, the output transistor conducts and pulls the output LOW. When IN+ rises above IN−, it releases the output and an external pull-up resistor establishes HIGH. This reference covers the classic LM393P and LM393D, with a 5 V threshold detector and a 2 V reference.
8Physical pins
LM393PPDIP-8
Manufacturer-referencedTexas Instruments
Pin diagram
Select a pin to explore its connection
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LM393PPDIP-8Top view
LM393DSOIC-8Top view
Click a lead or use the arrow keys. Top view
PIN 1 · Open-collector outputs
Open-collector outputOUT1
Function
Channel A sinks current when IN1− is above IN1+.
How to connect
Add a 10 kΩ pull-up to +5 V; read this node with a high-impedance input.
Electrical note
The IC does not actively drive HIGH.
PIN 2 · Comparison inputs
Inverting inputIN1−
Function
Channel A reference input in the illustrated circuit.
How to connect
Connect the 2.00 V divider node.
Electrical note
Keep both example inputs within 0–3 V at a 5 V supply.
PIN 3 · Comparison inputs
Non-inverting inputIN1+
Function
Channel A measured signal.
How to connect
Connect VIN and a common ground.
PIN 4 · Ground
Supply returnGND
Function
Ground reference for both comparators.
How to connect
Connect the supply return and bypass capacitor.
PIN 5 · Comparison inputs
Non-inverting inputIN2+
Function
Channel B positive input.
How to connect
Tie to GND when unused in this example.
PIN 6 · Comparison inputs
Inverting inputIN2−
Function
Channel B negative input.
How to connect
Connect to the same 2 V reference to give the unused channel a defined state.
PIN 7 · Open-collector outputs
Open-collector outputOUT2
Function
Channel B current-sinking output.
How to connect
Leave unconnected in the single-channel example.
Electrical note
Use a separate pull-up when using channel B.
PIN 8 · Supply
Positive supplyVCC
Function
Shared positive supply for both comparators.
How to connect
Apply +5 V; place 100 nF between pins 8 and 4.
Electrical note
Classic LM393 recommended supply: 2–30 V.
Key specifications
An open-collector output needs a pull-up resistor. It sinks current instead of sourcing a HIGH level.
Recommended supply2–30 V · classic LM393
Independent channels2 Open-collector outputs
Ambient range0–70 °C
Typical response1.3 µs · specified small-signal test
Package details
LM393P · PDIP-8
| Property | Details |
|---|---|
| Manufacturer | Texas Instruments |
| Part number | LM393P |
| Package | PDIP-8 |
| Connections | 8 pins |
| Mounting | Through-hole |
| Lead pitch | 2.54 mm |
| Package code | dip |
| Thermal reference | Board and package dependent; see manufacturer data |
Operating conditions
Classic LM393 · not the B revision
Manufacturer specifications 5 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Supply | 2–30 V | Single supply; example uses 5 V |
| Ambient temperature | 0 to +70°C | LM393 / LM393A grade |
| Input voltage range | 0 to VCC − 2 V | Recommended full-temperature range |
| Example input range | 0–3 V | At VCC = 5 V |
| Output HIGH | External pull-up required | Output transistor is off |
No specifications match. Try a parameter name or a unit.
TI SLCS005AH recommended conditions for the classic device.
Electrical characteristics
5 V supply unless stated
Manufacturer specifications 7 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Input offset voltage | 2 mV typical; 5 mV maximum | 25°C; VCC = 5–30 V |
| Offset over temperature | 9 mV maximum | 0–70°C |
| Input bias current | 25 nA typical; 250 nA maximum | Magnitude at 25°C |
| Output LOW voltage | 0.13 V typical; 0.40 V maximum | 4 mA sink; VID = −1 V; 25°C |
| Output LOW over temperature | 0.70 V maximum | Same 4 mA test; full range |
| Total supply current | 0.45 mA typical; 1 mA maximum | 5 V; unloaded; 25°C |
| Response time | 1.3 µs typical | 100 mV step; 5 mV overdrive; 5.1 kΩ pull-up; 15 pF |
No specifications match. Try a parameter name or a unit.
Response time and typical LOW voltage are not guaranteed operating limits.
Output behavior
Voltage difference and pull-up
Manufacturer specifications 5 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| IN+ < IN− | Output transistor ON | LOW; current flows through the pull-up |
| IN+ > IN− | Output transistor OFF | HIGH only with a pull-up or another defined load |
| Inputs nearly equal | Offset and noise matter | Output state is not guaranteed at exact equality |
| No pull-up; transistor OFF | Floating output | Do not call this HIGH |
| Noisy threshold | May switch repeatedly | Use calculated hysteresis for a stable transition |
No specifications match. Try a parameter name or a unit.
This example has no positive-feedback hysteresis.
Threshold detector values
Nominal 5 V example
Manufacturer specifications 6 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Upper reference resistor | 30 kΩ | From +5 V to VREF |
| Lower reference resistor | 20 kΩ | From VREF to ground |
| Reference voltage | 2.00 V | 5 × 20 / (30 + 20) |
| Output pull-up | 10 kΩ | From +5 V to OUT1 |
| Supply bypass | 100 nF | Close to pins 8 and 4 |
| Unused comparator | IN2+ to GND; IN2− to VREF | OUT2 unconnected |
No specifications match. Try a parameter name or a unit.
Divider tolerance, input bias and supply error affect the threshold.
Package and stress limits
LM393P · PDIP-8
Manufacturer specifications 6 parameters
Scroll sideways to see all columns.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Lead pitch | 2.54 mm | Through-hole; top view |
| Supply absolute maximum | 36 V | Stress rating; recommended maximum is 30 V |
| Output voltage absolute maximum | −0.3 to +36 V | Observe the load and current limits |
| Output current absolute maximum | 20 mA | Not a recommended design current |
| Junction temperature limit | 150°C | Absolute maximum |
| Storage temperature | −65 to +150°C | Unpowered storage |
No specifications match. Try a parameter name or a unit.
Use the manufacturer thermal data for the actual board and package.
Connections by function
Select a pin for its function, connection guidance and electrical notes.
Open-collector outputs2 pins
Comparison inputs4 pins
Ground1 pin
Supply1 pin
Open-collector outputs2 pins
Comparison inputs4 pins
Ground1 pin
Supply1 pin
LM393 at a glance
Follow the labeled connections and functional stages
How it works
3 stages · Explore one step at a time
Compare the two inputs
The differential input stage responds to IN+ minus IN−. No analog-to-digital converter or firmware is needed.
Sink current or release the node
A negative input difference turns the output transistor on. A positive difference turns it off. The external pull-up supplies the HIGH level.
Make a stable decision
Keep inputs in their common-mode range. Add positive-feedback hysteresis when a slowly changing or noisy signal would chatter around the threshold.
Step 1 of 3
Find the switching threshold
Adjust VIN and the reference. Remove the pull-up to see why it matters.
IN+ − IN−—
Output state—
Pull-up current—
Enable JavaScript to explore the comparator.
Violet: offset-sensitive transition · Amber: input outside the recommended range.
DC teaching model for channel A. The ±9 mV band uses the maximum input-offset magnitude over 0–70°C; it is uncertainty, not hysteresis. LOW uses a 0.13 V illustrative estimate. Propagation delay, input bias, leakage and noise are omitted.
LM393 in a circuit
A physical IC, a resistor reference and a clearly defined output.
Connect it, step by step
Follow the component values and pin connections
Build the reference
30 kΩ above and 20 kΩ below produce a nominal 2 V reference from 5 V.
Compare VIN
Connect the measured voltage to IN1+ and VREF to IN1−. VIN below 2 V makes OUT1 LOW.
Add the pull-up
Connect 10 kΩ from OUT1 to 5 V. Without it, the released output is floating rather than HIGH.
Inside LM393
Two differential channels with independent open-collector outputs.
Explore the circuit
Select a stage to see its role and connections
Differential input
Compare the two input voltages while respecting their valid range.
Open-collector switch
The collector is exposed at OUT. A LOW state sinks current; an off transistor releases the node.
Shared supply
Both channels use VCC pin 8 and GND pin 4, but each has its own inputs and output.
Selected packagePDIP-8LM393P
Physical connections8 pinsPackage-specific numbering
Reference collection6 tables29 parameters & pin functions
Pin reference
Signal names, electrical functions and connection guidance
Physical pin numbers8 pins
Scroll within the table to see all columns and rows.
| Pin | Signal | Type | Function & connection |
|---|---|---|---|
| OUT1 | Open-collector output | Channel A sinks current when IN1− is above IN1+.Connection guidanceAdd a 10 kΩ pull-up to +5 V; read this node with a high-impedance input. The IC does not actively drive HIGH. | |
| IN1− | Inverting input | Channel A reference input in the illustrated circuit.Connection guidanceConnect the 2.00 V divider node. Keep both example inputs within 0–3 V at a 5 V supply. | |
| IN1+ | Non-inverting input | Channel A measured signal.Connection guidanceConnect VIN and a common ground. | |
| GND | Supply return | Ground reference for both comparators.Connection guidanceConnect the supply return and bypass capacitor. | |
| IN2+ | Non-inverting input | Channel B positive input.Connection guidanceTie to GND when unused in this example. | |
| IN2− | Inverting input | Channel B negative input.Connection guidanceConnect to the same 2 V reference to give the unused channel a defined state. | |
| OUT2 | Open-collector output | Channel B current-sinking output.Connection guidanceLeave unconnected in the single-channel example. Use a separate pull-up when using channel B. | |
| VCC | Positive supply | Shared positive supply for both comparators.Connection guidanceApply +5 V; place 100 nF between pins 8 and 4. Classic LM393 recommended supply: 2–30 V. |
No pins match these filters. Try another signal name or reset the filters.
Operating conditions
Classic LM393 · not the B revision
Manufacturer-referenced values5 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Supply | 2–30 V | Single supply; example uses 5 V |
| Ambient temperature | 0 to +70°C | LM393 / LM393A grade |
| Input voltage range | 0 to VCC − 2 V | Recommended full-temperature range |
| Example input range | 0–3 V | At VCC = 5 V |
| Output HIGH | External pull-up required | Output transistor is off |
No specifications match. Try a parameter name or a unit.
TI SLCS005AH recommended conditions for the classic device.
Electrical characteristics
5 V supply unless stated
Manufacturer-referenced values7 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Input offset voltage | 2 mV typical; 5 mV maximum | 25°C; VCC = 5–30 V |
| Offset over temperature | 9 mV maximum | 0–70°C |
| Input bias current | 25 nA typical; 250 nA maximum | Magnitude at 25°C |
| Output LOW voltage | 0.13 V typical; 0.40 V maximum | 4 mA sink; VID = −1 V; 25°C |
| Output LOW over temperature | 0.70 V maximum | Same 4 mA test; full range |
| Total supply current | 0.45 mA typical; 1 mA maximum | 5 V; unloaded; 25°C |
| Response time | 1.3 µs typical | 100 mV step; 5 mV overdrive; 5.1 kΩ pull-up; 15 pF |
No specifications match. Try a parameter name or a unit.
Response time and typical LOW voltage are not guaranteed operating limits.
Output behavior
Voltage difference and pull-up
Manufacturer-referenced values5 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| IN+ < IN− | Output transistor ON | LOW; current flows through the pull-up |
| IN+ > IN− | Output transistor OFF | HIGH only with a pull-up or another defined load |
| Inputs nearly equal | Offset and noise matter | Output state is not guaranteed at exact equality |
| No pull-up; transistor OFF | Floating output | Do not call this HIGH |
| Noisy threshold | May switch repeatedly | Use calculated hysteresis for a stable transition |
No specifications match. Try a parameter name or a unit.
This example has no positive-feedback hysteresis.
Threshold detector values
Nominal 5 V example
Manufacturer-referenced values6 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Upper reference resistor | 30 kΩ | From +5 V to VREF |
| Lower reference resistor | 20 kΩ | From VREF to ground |
| Reference voltage | 2.00 V | 5 × 20 / (30 + 20) |
| Output pull-up | 10 kΩ | From +5 V to OUT1 |
| Supply bypass | 100 nF | Close to pins 8 and 4 |
| Unused comparator | IN2+ to GND; IN2− to VREF | OUT2 unconnected |
No specifications match. Try a parameter name or a unit.
Divider tolerance, input bias and supply error affect the threshold.
Package and stress limits
LM393P · PDIP-8
Manufacturer-referenced values6 parameters
Scroll within the table to see all columns and rows.
| Parameter | Value | Conditions / notes |
|---|---|---|
| Lead pitch | 2.54 mm | Through-hole; top view |
| Supply absolute maximum | 36 V | Stress rating; recommended maximum is 30 V |
| Output voltage absolute maximum | −0.3 to +36 V | Observe the load and current limits |
| Output current absolute maximum | 20 mA | Not a recommended design current |
| Junction temperature limit | 150°C | Absolute maximum |
| Storage temperature | −65 to +150°C | Unpowered storage |
No specifications match. Try a parameter name or a unit.
Use the manufacturer thermal data for the actual board and package.
No matching rowsTry a pin name, parameter, unit or test condition, or reset the filters.
Threshold and level detection
Compare a sensor voltage with a reference and feed the result to logic. Choose a pull-up voltage compatible with that logic.
Manufacturer application guideWindow detectors
Use both comparators for upper and lower limits. The output circuit determines how the two decisions combine.
Manufacturer application guideSlow sensor signals
Convert a temperature, light or position voltage into an alarm state. Hysteresis prevents noisy repeated transitions.
Manufacturer application guideTake it into ProTech
Find LM393 in the Components Library to place its schematic symbol and connect its pins.
Reference page · circuit simulation model not yet availableOpen ProTech