Pinout
ULN2803 Darlington array (DIP-18) pinout
Pins
- 1–8: IN1–IN8 (inputs, one per channel)
- 9: GND (the IC's own ground/substrate return — separate from COM)
- 10: COM (common flyback-diode cathode — tie to the driven loads' own supply+ for inductive loads; leave unconnected for purely resistive loads like LEDs)
- 11–18: OUT8–OUT1 (open-collector outputs, inverted relative to their input, each sinking up to ~500mA)
Specifications
| Example part | ULN2803A |
|---|---|
| Channels | 8 Darlington pairs, open-collector (sinking) outputs |
| Output voltage | 50 V max |
| Output current | 500 mA max per channel (total limited by package dissipation) |
| Saturation voltage | ≈ 0.9 V at 100 mA, 1.1 V at 200 mA, 1.3 V at 350 mA (typ) |
| Input | 2.7 kΩ series resistor built in; driven directly from 5 V TTL/CMOS |
| Flyback diodes | Built in, common cathode on COM (pin 10) |
| Package | DIP-18, SOIC-18 |
Notes
- The 8-channel version of the ULN2003 module above, in a bare DIP-18 — same idea (Darlington pairs driving relays/motors/solenoids straight from logic-level inputs), one more channel, no board attached.
- A quick wiring check once populated: IN1(pin1) sits directly opposite OUT1(pin18) across the package, IN8(pin8) opposite OUT8(pin11), and GND(9) opposite COM(10) — the pin numbering folds symmetrically around the package.
