St MicroElectronics ULN2803A Darlington Array 8 NPN DIP18

The St MicroElectronics ULN2803A Darlington Array is an eight-channel NPN Darlington transistor array housed in an 18-pin DIP (Dual In-line Package). It is designed to drive high-current loads directly from low-power digital logic circuits, making it suitable for interfacing microcontrollers and microprocessors with demanding peripheral devices.

Overview

Each of the eight Darlington pairs has common emitters and integral suppression (flyback) diodes, which support safe switching of inductive loads such as relays, solenoids, stepper motors, and lamps. The built-in diodes remove the need for external flyback diodes, which can simplify circuit design. The array offers a peak load current rating of 600mA and a continuous current rating of 500mA per channel, with outputs capable of withstanding up to 50V in the OFF state.

Key Features

• Simplified Interfacing: Includes 2.7kOhm input resistors for direct connection to 5V TTL and CMOS logic families.
• Optimised Board Layout: Inputs are pinned opposite the outputs, which simplifies printed circuit board (PCB) routing.
• Enhanced Current Capacity: Outputs can be paralleled to achieve a higher total current capability.
• Wide Operating Range: Rated for an operating ambient temperature range of -20°C to +85°C, with a total power dissipation (Pd) of 2.25W.

Dimensions and Weight

The array measures 3.3 (width), 1.5 (depth) and 4.3 (height), and weighs 2 gm.

The ULN2803A is a practical choice where a logic-level device needs to switch relays, solenoids, stepper motors, or lamps from a single compact 18-pin package.