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DIP-16 / SOP-16 · ULN2003
ActiveDarlington Transistor Arrays
ULN2003
Texas Instruments · DIP-16 / SOP-16 · Darlington Transistor Arrays
Price on Request
Get a competitive quote within 24 hours. Volume discounts available. Shenzhen stock ships in 1-2 business days.
Overview
The ULN2003 is a monolithic high-voltage, high-current Darlington transistor array containing seven independent open-collector Darlington pairs with common-emitter and integrated clamp diodes for inductive loads. Each channel can sink 500 mA at up to 50 V collector-emitter, with inputs compatible with TTL and 5 V CMOS logic — meaning you can drive relays, stepper motors, solenoids, lamps and other inductive loads directly from a microcontroller's GPIO pins without external transistors or flyback diodes.
The integrated clamp diodes are the ULN2003's killer feature: they connect each output to the COM pin (pin 9), which you tie to the inductive load's positive supply. When the Darlington switches off, the collapsing magnetic field in a relay coil or motor winding generates a reverse voltage spike; the clamp diode safely dissipates this into the COM rail, protecting both the ULN2003 and the MCU. Without these diodes you would need seven external 1N4148 flybacks, adding cost, board space and reliability risk.
Input current is about 1 mA at 5 V logic high (thanks to the internal 2.7 kΩ base resistor and Darlington gain), well within MCU GPIO limits. Output saturation voltage is 0.9-1.3 V at 350 mA, which means you lose about 0.4 W per channel — plan for that in your power budget and heatsink the SOP-16 or DIP-16 package's exposed pad if driving multiple channels simultaneously.
Variants: ULN2003A (7 channels, most common), ULN2004A (higher-gain inputs for 6-15 V CMOS), ULN2803A (8 channels in 18-pin package). All are pin-compatible within their family.
Our Shenzhen stock includes TI ULN2003ADR (SOP-16), ST ULN2003A, and onsemi MC1413BDG. MOQ 2,500 pcs on reel or 100 pcs loose.
Key Features
- Seven Darlington channels, 500 mA / 50 V each
- Integrated clamp diodes for inductive loads
- TTL / 5 V CMOS compatible inputs (~1 mA drive)
- Common-emitter COM pin for shared load supply
Typical Applications
- Relay banks in home automation, industrial control and HVAC
- Unipolar stepper motor drivers (28BYJ-48 and similar)
- Solenoid and small DC motor switching
- LED matrix and lamp drivers where common-anode topology fits
- PLC output modules
Specifications
- Channels
- 7
- Output Current per Channel
- 500 mA
- Output Voltage (Max)
- 50 V
- Input Compatibility
- TTL / CMOS
- Clamp Diodes
- Integrated
- Operating Temperature
- -20 to 85 °C
- Mounting Type
- Through Hole / Surface Mount
- Pins
- 16
- RoHS
- Compliant
Procurement Tips
For 3.3 V MCU designs, spec ULN2004A instead of ULN2003 — its higher-gain inputs are optimized for lower-voltage CMOS logic and turn on more reliably at 3.3 V.
Frequently Asked Questions
Can ULN2003 drive a bipolar stepper motor?
No, not directly. ULN2003 sinks current to ground and cannot reverse current direction. It works perfectly with unipolar 5-wire steppers (like the ubiquitous 28BYJ-48). For bipolar 4-wire steppers, use an H-bridge driver like A4988, DRV8825 or L293D.
Why does my ULN2003 output stay at ~1 V when "off"?
It's not off — the Darlington pair is saturated, which drops about 0.9-1.3 V between collector and emitter. This is normal. If your load needs true 0 V when off, use a MOSFET-based driver (like MIC2981 for high-side, or a discrete 2N7002 array).
What is the COM pin for?
COM (pin 9) connects to the positive side of your inductive loads. It's the common cathode for all seven internal clamp diodes. For resistive loads (LEDs with series resistors, incandescent lamps) you can leave COM floating or tie it to Vcc — either works.
Can I parallel channels for higher current?
Yes, tie two or more inputs together and two or more outputs together. The Darlington pairs share current approximately evenly due to their positive temperature coefficient. Two channels give 1 A, three give 1.5 A, etc. Total package limit is 2.5 A.
ULN2003 vs L293D — what's the difference?
L293D is a quad half-H-bridge (bidirectional current), rated 600 mA per channel with 36 V max. ULN2003 is 7 unidirectional open-collector channels at 500 mA / 50 V. Use L293D for DC motors needing direction control; use ULN2003 for relays, unipolar steppers, and high-side-switched loads.
MOQ and lead time?
MOQ 2,500 pcs on reel for ULN2003ADR (SOP-16), or 100 pcs loose. TI authorized 8-16 weeks; Shenzhen stock 1-2 days.
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