Technical Articles

What is ULN2003?

The ULN2003 is a popular integrated circuit that consists of seven Darlington transistor pairs which can be used to interface high-current loads with low-level logic signals. It is commonly used in applications where there is a need to control devices such as relays, stepper motors, and solenoids.

How Does the ULN2003 Work?

The ULN2003 works by using the Darlington transistor configuration, which provides a high current gain and a low saturation voltage. This allows it to handle higher currents than a single transistor can handle alone. Each pair of transistors is connected so that when one is turned on, the other is turned off, providing a means of controlling a larger load with a small input signal. The ULN2003 also includes a built-in clamp diode for each transistor pair, which protects the circuit from voltage spikes generated by the inductive load.

Applications of the ULN2003

The ULN2003 is widely used in various applications due to its versatility and reliability. Some common applications include:

1. Relay Driving: The ULN2003 can drive electromagnetic relays, making it suitable for home automation systems, industrial control systems, and robotics.

2. Stepper Motor Control: By connecting the appropriate pins of the ULN2003 to the stepper motor, precise control of its movement can be achieved. This makes it useful in 3D printers, CNC machines, and robotic arms.

3. Solenoid Control: The ULN2003 can be used to control solenoids in applications such as door locks, valves, and pneumatic systems.


The ULN2003 is a versatile and reliable integrated circuit that allows for the easy control of high-current loads using low-level logic signals. With its Darlington transistor configuration and built-in clamp diodes, it is well-suited for a variety of applications ranging from relay driving to stepper motor control and solenoid control. Its ease of use and wide availability make it a popular choice among electronics enthusiasts and professionals alike.



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