ULN2803 8-Channel Darlington Sink Driver IC

The  ULN2803 designed as a  high-voltage, high-current Darlington arrays each containing eight NPN Darlington pairs. The device features common emitter and open collector outputs with suppression diodes used for inductive loads and also perfectly suited for interfacing between low-level logic circuitry and high power loads.  Basically, load comprises of relays DC motors, filament lamps, LED displays, printer hammers, and high power buffers. Moreover, these devices are perfect for driving a wide range of loads including solenoids, relays, lamps, small motors, and LEDs and high-power buffers.Meanwhile, the ULN2803 devices have a 2.5-kΩ series base resistor to allow operation directly from TTL or CMOS devices that use supply voltages of 5 V or 3.3 V. Thus IC  interface easily with the standard logic level for TTL or 5VCMOS devices.

Each Darlington feature high-voltage outputs with common-cathode clamp diodes for switching inductive loads. The collector-current rating of each Darlington pair is 500 mA. And can withstand at least 50 V in the OFF state.  To acheive higher current capability, Outputs may be paralleled. The inputs made pinned opposite the outputs in the IC package to simplify the application board layout.  Moreover, the ULN2803 manufactured in an 18-pin DIP package with a copper lead frame to reduce thermal resistance. And feature the convenient input-opposite-output pinout to simplify board layout.

A Darlington pair designed as a multi-transistor configuration circuit. It comprises of two bipolar transistors with the emitter of one transistor connected to the base of the other.  Such that the current amplified by the first transistor amplified further by the second one. The collectors of both transistors are connected together. Thus this configuration employs much higher current gain than each transistor taken separately.

Applications

• Relay Drivers
• Stepper and DC Brushed Motor Drivers
• Lamp Drivers
•  Display Drivers (LED and Gas Discharge)
• Line Drivers
•  Logic Buffers