ULN2803A – STMicroelectronics

The STMicroelectronics ULN2803A is a high-voltage, high-current Darlington transistor array consisting of eight NPN Darlington pairs, each featuring a common-emitter configuration. This through-hole packaged device is specifically designed for interfacing low-level logic signals (typically TTL or 5V CMOS) to higher voltage/current loads. Each output channel is rated for a maximum output voltage of 50V and can sink up to 500mA of continuous output current. Internal suppression diodes protect the Darlington transistors against inductive load kickback, simplifying circuit design and improving reliability. Commonly used for driving relays, solenoids, lamps, and stepper motors, the ULN2803A operates reliably across a temperature range of –20°C to 85°C, offering a robust and cost-effective solution for applications requiring high-current switching capabilities from a low-power control signal. Its inherent gain and protection features minimize the need for external components.