Description

ULN2803 IC

The ULN2803 IC is a popular eight-channel Darlington transistor array used when a microcontroller or digital circuit needs to control loads that require more current than its output pins can safely provide.

It contains eight NPN Darlington transistor pairs in a single package. Each channel works as a low-side switch: a HIGH logic signal at an input activates the corresponding output and allows current to flow through the connected load to ground.

The ULN2803 is particularly useful for controlling relay coils, indicator lamps, LED arrays, small solenoids and other compatible inductive loads. Its built-in clamp diodes help protect the circuit from voltage spikes produced when switching inductive loads.

It can be used with Arduino boards and other 5V logic systems. For reliable operation, check the load current, supply voltage and IC temperature against the datasheet limits.

Technical Specifications

Important: The 500mA rating is not a guarantee that all eight channels can continuously handle 500mA simultaneously. Total power dissipation, ambient temperature, PCB layout and load conditions limit practical current.

Pin Configuration (DIP-18)

Key Features

• Eight independent Darlington driver channels.

• 50V maximum output voltage rating.

• 500mA continuous collector-current rating per channel under specified conditions.

• Built-in suppression diodes for inductive loads.

• 2.7kΩ input resistors for 5V TTL and CMOS compatibility.

• Convenient DIP-18 package for through-hole circuits.

• Multiple outputs can be paralleled when the design’s thermal and electrical limits are respected.

Applications

• Arduino relay control circuits.

• DC solenoid and electromagnetic load switching.

• Stepper motor driver circuits.

• LED displays and LED arrays.

• Digital logic interfacing.

• Small lamp and indicator control.

• Microcontroller output expansion.

How to Use / Setup

1. Connect pin 9 to circuit ground.

2. Connect a microcontroller output to one of the ULN2803 input pins.

3. Connect the load between its positive supply and the corresponding ULN2803 output.

4. Connect the load supply ground to the circuit ground.

5. For inductive loads such as relay coils, connect pin 10 (COM) to the positive load supply so the internal clamp diodes can operate.

6. Apply the control signal to switch the corresponding load.

Precautions

• Do not exceed the specified voltage and current ratings.

• Check total IC power dissipation when operating multiple channels.

• Remember that the ULN2803 output switches toward ground; it does not provide a positive output voltage.

• Use a suitable external power supply for relays and other loads.

• Connect COM correctly when driving inductive loads.

• Do not use this IC as a direct replacement for an H-bridge motor driver when bidirectional motor control is required.

YouTube Tutorial

Watch ULN2803 IC Arduino and Relay Driver Tutorials

Buy in Pakistan

Looking for a ULN2803 IC in Pakistan for your electronics or Arduino project? Explore electronic components and ICs at Electroway.org or through the Electroway App.

4. Product Summary

The ULN2803 is an 8-channel Darlington transistor array IC used to control relays, solenoids, LED displays and other compatible loads using low-current logic signals. It is a useful component for Arduino projects, microcontroller circuits and electronics prototyping.