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ULN2803A Darlington Array

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by Ray

Eight NPN Darlington pairs with 50 V, 500 mA outputs and clamp diodes for inductive loads.

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ULN2803A

Texas Instruments · Transistor Array / Driver · SOIC-18

The ULN2803A is an array of eight NPN Darlington pairs with high-voltage, high-current outputs and common-cathode flyback clamp diodes. Each channel sinks up to 500 mA at 50 V from a logic-level input, making it a standard way to drive relays, solenoids, unipolar stepper motors, and LED banks.

Pinout

Pin Name Type Function
1 1B input Channel 1 Darlington base input. Drives channel 1 output through 2.7kΩ series base resistor; compatible with TTL/CMOS logic up to VI(max)=30V.
2 2B input Channel 2 Darlington base input. Drives channel 2 output through 2.7kΩ series base resistor.
3 3B input Channel 3 Darlington base input. Drives channel 3 output through 2.7kΩ series base resistor.
4 4B input Channel 4 Darlington base input. Drives channel 4 output through 2.7kΩ series base resistor.
5 5B input Channel 5 Darlington base input. Drives channel 5 output through 2.7kΩ series base resistor.
6 6B input Channel 6 Darlington base input. Drives channel 6 output through 2.7kΩ series base resistor.
7 7B input Channel 7 Darlington base input. Drives channel 7 output through 2.7kΩ series base resistor.
8 8B input Channel 8 Darlington base input. Drives channel 8 output through 2.7kΩ series base resistor.
9 GND power_in Common emitter of all eight Darlington pairs. Typically tied to system ground; also serves as the return for the input logic reference.
10 COM power_in Common cathode of the internal free-wheeling clamp diodes. Tie to the inductive-load supply (VSUP) so kickback energy is clamped when the Darlington turns off; may be left open when driving purely resistive loads.
11 8C output Channel 8 Darlington open-collector output. Sinks up to 500mA per channel from loads returned to COM/VSUP (≤50V).
12 7C output Channel 7 Darlington open-collector output. Sinks up to 500mA per channel.
13 6C output Channel 6 Darlington open-collector output. Sinks up to 500mA per channel.
14 5C output Channel 5 Darlington open-collector output. Sinks up to 500mA per channel.
15 4C output Channel 4 Darlington open-collector output. Sinks up to 500mA per channel.
16 3C output Channel 3 Darlington open-collector output. Sinks up to 500mA per channel.
17 2C output Channel 2 Darlington open-collector output. Sinks up to 500mA per channel.
18 1C output Channel 1 Darlington open-collector output. Sinks up to 500mA per channel.

Key specifications

Parameter Value
Type 8-channel NPN Darlington array (sink)
Output voltage 50 V max
Output current 500 mA per channel (peak)
Input Logic-level (2.7 V and 5 V compatible)
Clamp diodes Integrated common-cathode (COM pin)
Operating temperature -40 C to 85 C

Ordering variants

Same part, different packaging or reel option.

  • ULN2803ADW

CAD (KiCad official)

  • Symbol: uln2803a.kicad_sym
  • Footprint: uln2803a.kicad_mod
  • 3D model: SOIC-18 wide body from KiCad Package_SO/SOIC-18W_7.5x11.6mm_P1.27mm.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Texas Instruments datasheet (21 pp, sha256 12d7302794e2a590, retrieved 2026-08-17, tier: manufacturer)
  • Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF