ULN2004ADR Discrete Semiconductor Products

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The ULN2004ADR is a high voltage, high current Darlington transistor array. It consists of seven NPN Darlington pairs that feature high-voltage outputs with common-cathode clamp diodes for switching inductive loads. Each Darlington pair uses one internal suppressor diode to eliminate the need for an external diode, which is often required when replacing multiple discrete transistors, thereby reducing system size, power consumption, and cost. With a wide operating voltage, high output current capability, and the ability to drive a wide range of loads, this electronic component offers a wide range of applications.

Application Field

The ULN2004ADR can be used in numerous applications, ranging from audio amplifiers to motor and relay control. It can be used to amplify audio signals, providing an efficient, low-cost way to boost audio volume. It can also be used to control motors, stepping motors, and relays, making it the ideal solution for a variety of applications in home automation, automotive, and industrial automation. It can also be used to drive LEDs and other loads, providing an interesting range of options for lighting and display applications.

Working Principle

The ULN2004ADR is a seven-channel Darlington transistor array. Each channel consists of an NPN Darlington pair and a diode protection circuit. The Darlington pairs of the array are activated by a signal applied to the corresponding control input. The Darlington pair features one emitter, two collectors, and one base. When a voltage is applied to the base, current flow will increase exponentially and will cause the transistor to be activated. This Darlington pair functions as a high current and a high-voltage switch with a low control current, and is often used in applications where a high voltage is required, such as in the control of motors or solenoids.

The diode protection circuit is used to protect the Darlington pair from short-circuit damage, particularly when switching inductive loads such as motors or relays. This circuit consists of a common-cathode clamp diode, which is connected in parallel to the emitter-collector circuit of the transistor. When the voltage across the transistor\'s emitter-collector exceeds the forward voltage of the diode, the diode is forward biased and conducts, protecting the transistor from short circuits.

The ULN2004ADR is an ideal solution for a variety of low-voltage, low-power applications where current and voltage needs to be controlled. Its easy integration, low cost, and high reliability make it the perfect choice for most switching applications.

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