Part of the Day · ULN2003A — SOIC-16 7-channel Darlington transistor array (marking ULN2003A)

Part of the Day · 2026-10-29

A driver IC with seven NPN Darlington transistors and clamp diodes for absorbing back-EMF in one chip. It lets a 5V MCU signal switch loads such as relays, stepper motors and lamps directly, up to 50V·500mA. The TI SOIC-16 (D) part is marked ULN2003A.

Actual size

↓ Actual size, left edge aligned to 0 on the ruler

One ruler tick = 1mm. On PC this is actual size on a 24-inch FHD monitor at 100% zoom; on iPhone it adjusts automatically. For other screens, use “Calibrate ruler” below.

Enlarged (SOIC-16 · top view · approx. 10×)

Pins 1~7 1B~7B (inputs, Darlington bases) · 8 E (common emitter, usually GND) · 9 COM (common cathode of the clamp diodes, connect to the inductive load supply) · 10~16 7C~1C (outputs, Darlington collectors — 1B drives pin 16 1C, 7B drives pin 10 7C)

Package SOIC-16 · Marking ULN2003A

Key specifications

Values are from the Texas Instruments datasheet.

Marking and pins

Marking code ULN2003A · Pins 1~7 1B~7B (inputs, Darlington bases) · 8 E (common emitter, usually GND) · 9 COM (common cathode of the clamp diodes, connect to the inductive load supply) · 10~16 7C~1C (outputs, Darlington collectors — 1B drives pin 16 1C, 7B drives pin 10 7C)

Typical uses

• Driving relays and solenoids
• Driving stepper motors and DC motors
• Driving lamps and LED indicators, logic buffers

Companion & similar parts

• ULN2003AN — Same chip in PDIP-16 (19.30 × 6.35mm, through-hole)
• ULN2003ANSR — Same chip in SOP-16 (10.30 × 5.30mm)
• ULN2003AI — -40 ~ 105℃ version from the same datasheet
• ULN2004A — 10.5kΩ input resistor — for 6 ~ 15V CMOS

The outputs only sink current to GND (open collector), so the load goes between the supply (+) and the output pin. For coil loads such as relays and motors, connect COM (pin 9) to that load supply so the clamp diodes can absorb the back-EMF. Each channel handles up to 500mA, but keep the total current flowing into E (pin 8) below 2.5A. The datasheet notes that channels can be paralleled for higher current.