ULN2003ASeven-channel Darlington driver
Let low-power logic control relays, lamps and coils.
ULN2003A combines seven NPN Darlington pairs in one 16-pin package. A logic HIGH turns on its matching collector output, allowing the IC to sink current from an external load. Each channel includes a 2.7 kΩ input resistor and a clamp diode. The diode cathodes share COM, which connects to the positive supply when driving relay or motor coils. This reference covers ULN2003AN and ULN2003AD. A 12 V relay example explains the common ground, voltage drop and package power budget.
Logic inputsEmitter returnFlyback protectionCollector outputs
ULN2003ANPDIP-16Top view
ULN2003ADSOIC-16Top view
Click a lead or use the arrow keys. Top view
PIN 1 · Logic inputs
Darlington input1B
Function
Drives channel 1 through an internal 2.7 kΩ base resistor.
How to connect
Connect to a 5 V logic output. Tie unused inputs LOW.
Electrical note
HIGH turns the corresponding low-side output on.
PIN 2 · Logic inputs
Darlington input2B
Function
Drives channel 2 through an internal 2.7 kΩ base resistor.
How to connect
Connect to a 5 V logic output. Tie unused inputs LOW.
Electrical note
HIGH turns the corresponding low-side output on.
PIN 3 · Logic inputs
Darlington input3B
Function
Drives channel 3 through an internal 2.7 kΩ base resistor.
How to connect
Connect to a 5 V logic output. Tie unused inputs LOW.
Electrical note
HIGH turns the corresponding low-side output on.
PIN 4 · Logic inputs
Darlington input4B
Function
Drives channel 4 through an internal 2.7 kΩ base resistor.
How to connect
Connect to a 5 V logic output. Tie unused inputs LOW.
Electrical note
HIGH turns the corresponding low-side output on.
PIN 5 · Logic inputs
Darlington input5B
Function
Drives channel 5 through an internal 2.7 kΩ base resistor.
How to connect
Connect to a 5 V logic output. Tie unused inputs LOW.
Electrical note
HIGH turns the corresponding low-side output on.
PIN 6 · Logic inputs
Darlington input6B
Function
Drives channel 6 through an internal 2.7 kΩ base resistor.
How to connect
Connect to a 5 V logic output. Tie unused inputs LOW.
Electrical note
HIGH turns the corresponding low-side output on.
PIN 7 · Logic inputs
Darlington input7B
Function
Drives channel 7 through an internal 2.7 kΩ base resistor.
How to connect
Connect to a 5 V logic output. Tie unused inputs LOW.
Electrical note
HIGH turns the corresponding low-side output on.
PIN 8 · Emitter return
Common emitterE
Function
Shared emitter and substrate return for all seven channels.
How to connect
Connect to load-supply ground and controller ground.
Electrical note
This is the high-current return path; route it appropriately.
PIN 9 · Flyback protection
Clamp diode commonCOM
Function
Common cathodes of the seven internal flyback diodes.
How to connect
Connect to the positive relay or motor-coil supply for inductive loads.
Electrical note
COM is not a logic supply pin and is not ground.
PIN 10 · Collector outputs
Open-collector driver7C
Function
Collector output of channel 7.
How to connect
Connect between the load and the IC; the other load terminal goes to the positive load supply.
Electrical note
Sinks current only. Allow Darlington voltage drop and package heating.
PIN 11 · Collector outputs
Open-collector driver6C
Function
Collector output of channel 6.
How to connect
Connect between the load and the IC; the other load terminal goes to the positive load supply.
Electrical note
Sinks current only. Allow Darlington voltage drop and package heating.
PIN 12 · Collector outputs
Open-collector driver5C
Function
Collector output of channel 5.
How to connect
Connect between the load and the IC; the other load terminal goes to the positive load supply.
Electrical note
Sinks current only. Allow Darlington voltage drop and package heating.
PIN 13 · Collector outputs
Open-collector driver4C
Function
Collector output of channel 4.
How to connect
Connect between the load and the IC; the other load terminal goes to the positive load supply.
Electrical note
Sinks current only. Allow Darlington voltage drop and package heating.
PIN 14 · Collector outputs
Open-collector driver3C
Function
Collector output of channel 3.
How to connect
Connect between the load and the IC; the other load terminal goes to the positive load supply.
Electrical note
Sinks current only. Allow Darlington voltage drop and package heating.
PIN 15 · Collector outputs
Open-collector driver2C
Function
Collector output of channel 2.
How to connect
Connect between the load and the IC; the other load terminal goes to the positive load supply.
Electrical note
Sinks current only. Allow Darlington voltage drop and package heating.
PIN 16 · Collector outputs
Open-collector driver1C
Function
Collector output of channel 1.
How to connect
Connect between the load and the IC; the other load terminal goes to the positive load supply.
Electrical note
Sinks current only. Allow Darlington voltage drop and package heating.
At a glance
Seven-channel Darlington driver
The chip switches the low side of each load. COM serves the clamp diodes; it does not power the input logic.
7 NPN Darlington pairsIndependent drivers
50 V · rated maximumCollector voltage
500 mA · thermal derating requiredSingle-output peak rating
−40–70 °CULN2003A ambient range
Operating profile
ULN2003AN
Connection reference
Key parameters and their test conditions
- Channel 1
- 1B pin 1 → 1C pin 16Conditions / notes: HIGH input turns the output sink on
- Channel 2
- 2B pin 2 → 2C pin 15Conditions / notes: Same behavior
- Channel 3
- 3B pin 3 → 3C pin 14Conditions / notes: Same behavior
- Channel 4
- 4B pin 4 → 4C pin 13Conditions / notes: Same behavior
- Channel 5
- 5B pin 5 → 5C pin 12Conditions / notes: Same behavior
- Channel 6
- 6B pin 6 → 6C pin 11Conditions / notes: Same behavior
Package details
Follows the selected physical package
- Manufacturer
- Texas Instruments
- Part number
- ULN2003AN
- Package
- PDIP-16
- Connections
- 16 pins
- Mounting
- Through-hole
- Lead pitch
- 2.54 mm
- Package code
- dip
- Thermal reference
- Board and package dependent; see manufacturer data
Connections by function
Select a pin to open its function, electrical notes and wiring guidance.
Logic inputs7 pins
Emitter return1 pins
Flyback protection1 pins
Collector outputs7 pins
Logic inputs7 pins
Emitter return1 pins
Flyback protection1 pins
Collector outputs7 pins
Drive the input
A logic HIGH supplies base current through the internal 2.7 kΩ resistor. Two transistors provide current gain in each channel.
Complete the load current path
The collector sinks current through the load to E. Current flows from the load supply, through the relay coil, through the Darlington pair and back to ground.
Handle switch-off energy
When a coil turns off, its current briefly continues through the internal clamp diode to COM. Connect COM to the coil supply and consider how that supply absorbs the energy.
The 500 mA rating is for one output and does not mean every channel can run at 500 mA continuously. Check duty cycle, temperature, package and the total emitter current.
Switch seven loads independently
Click an input. Follow its collector current and the combined power budget.
Active channels0 / 7
Total coil current0 mA
Output-stage dissipation0 mW
Enable JavaScript to try the drivers.
Illustrative steady-state relay loads. Each coil is 240 Ω on a 12 V supply; the driver drop is fixed at 0.90 V. No relay mechanics, flyback waveform, temperature rise or saturation curve is simulated. COM is connected to the load supply.
Pin reference
Select a pin to explore its function and connection.
16 pins
| Pin | Signal | Type | Function |
|---|---|---|---|
| 1B | Darlington input | Drives channel 1 through an internal 2.7 kΩ base resistor. | |
| 2B | Darlington input | Drives channel 2 through an internal 2.7 kΩ base resistor. | |
| 3B | Darlington input | Drives channel 3 through an internal 2.7 kΩ base resistor. | |
| 4B | Darlington input | Drives channel 4 through an internal 2.7 kΩ base resistor. | |
| 5B | Darlington input | Drives channel 5 through an internal 2.7 kΩ base resistor. | |
| 6B | Darlington input | Drives channel 6 through an internal 2.7 kΩ base resistor. | |
| 7B | Darlington input | Drives channel 7 through an internal 2.7 kΩ base resistor. | |
| E | Common emitter | Shared emitter and substrate return for all seven channels. | |
| COM | Clamp diode common | Common cathodes of the seven internal flyback diodes. | |
| 7C | Open-collector driver | Collector output of channel 7. | |
| 6C | Open-collector driver | Collector output of channel 6. | |
| 5C | Open-collector driver | Collector output of channel 5. | |
| 4C | Open-collector driver | Collector output of channel 4. | |
| 3C | Open-collector driver | Collector output of channel 3. | |
| 2C | Open-collector driver | Collector output of channel 2. | |
| 1C | Open-collector driver | Collector output of channel 1. |
No pins match. Try a signal name or choose All pins.
Connection reference
Input and output pairs
Manufacturer specifications 9 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Channel 1 | 1B pin 1 → 1C pin 16 | HIGH input turns the output sink on |
| Channel 2 | 2B pin 2 → 2C pin 15 | Same behavior |
| Channel 3 | 3B pin 3 → 3C pin 14 | Same behavior |
| Channel 4 | 4B pin 4 → 4C pin 13 | Same behavior |
| Channel 5 | 5B pin 5 → 5C pin 12 | Same behavior |
| Channel 6 | 6B pin 6 → 6C pin 11 | Same behavior |
| Channel 7 | 7B pin 7 → 7C pin 10 | Same behavior |
| Common emitter | E pin 8 | Ground return |
| Diode common | COM pin 9 | Positive inductive-load supply |
No specifications match. Try a parameter name or a unit.
The physical output order is reversed across the package.
Electrical characteristics
ULN2003A · 25°C
Manufacturer specifications 8 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Input resistor | 2.7 kΩ | Internal series base resistor |
| ON input voltage | 2.4 V maximum | IC = 200 mA; VCE = 2 V |
| ON input voltage | 3.0 V maximum | IC = 300 mA; VCE = 2 V |
| Saturation voltage | 0.9 V typical; 1.1 V maximum | 100 mA collector; 250 µA input |
| Saturation voltage | 1.0 V typical; 1.3 V maximum | 200 mA collector; 350 µA input |
| Saturation voltage | 1.2 V typical; 1.6 V maximum | 350 mA collector; 500 µA input |
| Input current | 0.93 mA typical; 1.35 mA maximum | VI = 3.85 V |
| Clamp diode forward voltage | 1.7 V typical; 2.0 V maximum | IF = 350 mA |
No specifications match. Try a parameter name or a unit.
Use the specified drive current when interpreting the saturation-voltage limits.
Operating and stress limits
Do not add seven maximum channel currents
Manufacturer specifications 8 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Collector-emitter voltage | 0–50 V | Recommended range; observe transient margin |
| Recommended junction range | −40 to +125°C | Package thermal design matters |
| Peak collector current | 500 mA per channel | Absolute maximum; see duty-cycle curves |
| Total emitter-terminal current | 2.5 A magnitude | Absolute maximum, not a continuous thermal rating |
| Input voltage | 30 V maximum | Absolute maximum; normal control is 5 V logic |
| Clamp current | 500 mA maximum | Absolute maximum per clamp path |
| Maximum junction temperature | 150°C | Absolute maximum |
| Storage | −65 to +150°C | Unpowered |
No specifications match. Try a parameter name or a unit.
A load’s voltage, current and duty cycle must all fit the complete system.
Relay example calculations
12 V supply · 240 Ω coil
Manufacturer specifications 6 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Illustrative driver drop | 0.90 V | Fixed teaching estimate; actual value varies |
| Coil voltage when ON | 11.10 V | 12 − 0.90 |
| Coil current when ON | 46.25 mA | 11.10 / 240 |
| Driver dissipation per channel | 41.6 mW | 0.90 × 0.04625 |
| Seven channels ON | 323.75 mA; 291.4 mW | Collector current and output-stage dissipation |
| Relay selection | Check guaranteed pickup voltage | Allow supply, coil and driver tolerances |
No specifications match. Try a parameter name or a unit.
These are DC estimates, not a relay pickup guarantee or transient calculation.
Package and thermal reference
ULN2003AN · PDIP-16
Manufacturer specifications 5 parameters
| Parameter | Value | Conditions / notes |
|---|---|---|
| Lead pitch | 2.54 mm | Through-hole; top view |
| PDIP-16 RθJA | 66.7°C/W | TI standardized test board |
| SOIC-16 RθJA | 88.6°C/W | TI standardized test board |
| Board dependence | Copper and airflow change temperature | Do not treat RθJA as a universal enclosure constant |
| Unused channels | Inputs LOW; collectors unconnected | Do not leave control inputs floating |
No specifications match. Try a parameter name or a unit.
See the PDF for duty-cycle derating and the exact thermal measurement conditions.
Relay banks
Drive several relay coils from logic. Match coil voltage, pickup requirements and current to the complete driver design.
Manufacturer application guideUnipolar stepper motors
Sequence the coil channels and connect the winding common to the load supply. This is a low-side array, not a bipolar H-bridge.
Manufacturer application guideLamps and indicators
Switch lamps or suitably current-limited LED loads. Account for startup current and the Darlington voltage drop.
Manufacturer application guideTake it into ProTech
Find ULN2003A in the Components Library to place its schematic symbol and connect its pins.
Reference page · circuit simulation model not yet availableOpen ProTech