Part Number: ULN2803AN

Manufacturer: Texas Instruments

Description: TRANSISTOR 8NPN DARL 50V 0.5A 18DIP

Shipped from: Shenzhen/HK Warehouse

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Technical Specifications of ULN2803AN

Datasheet  ULN2803AN datasheet
Category Discrete Semiconductor Products
Family Transistors – Bipolar (BJT) – Arrays
Manufacturer Texas Instruments
Packaging Tube
Transistor Type 8 NPN Darlington
Current – Collector (Ic) (Max) 500mA
Voltage – Collector Emitter Breakdown (Max) 50V
Vce Saturation (Max) @ Ib, Ic 1.6V @ 500μA, 350mA
Current – Collector Cutoff (Max)
DC Current Gain (hFE) (Min) @ Ic, Vce
Power – Max
Frequency – Transition
Mounting Type Through Hole
Package / Case 18-DIP (0.300″, 7.62mm)
Supplier Device Package 18-PDIP

ULN2803AN Introduction

Do you need to power relays, lights, and motors from your microcontroller or logic device and want a robust and flexible solution? The ULN2803AN is the one you want. This device’s eight NPN Darlington pairs have a collector current rating of 500 mA each and high-voltage outputs with common-cathode clamp diodes, making them ideal for switching inductive loads. It’s great for various uses because of its interoperability with different logic types and series base resistors for each Darlington pair. Find out how the ULN2803AN may propel your next project forward by reading on to learn more about its features and functions.

ULN2803AN Description

The ULN2803A is a Darlington transistor array that handles large currents at high voltages. This device uses eight NPN Darlington pairs with high-voltage common-cathode clamp diodes for switching inductive loads. while the device itself consists of a single NPN transistor. Each Darlington pair can withstand a collector current of 500 mA. The current capacity can be increased by connecting the Darlington pairs in parallel. There are various uses for logic buffers and drivers, such as relay drivers, hammer drivers, lamp drivers, display drivers (LED and gas discharge), and line drivers. Each Darlington pair in the ULN2803A has a series base resistor of 2.7 k, allowing it to work directly with TTL or 5-V CMOS circuitry.

ULN2803AN Features

  • A Rated Collector Current of 500 mA (Single Output).
  • 50 V is the high-voltage output.
  • Diodes for output clamping
  • Logic-compatible inputs of many kinds.
  • Relay-Driver Programs are similar to the ULN2800A Series.

Detailed Description

This commonplace technology has established its universality and adaptability across various applications. This is because it integrates 8 Darlington transistors, each of which can sink up to 500 mA and has a wide GPIO range. The ULN2803A comprises 7 pairs of NPN Darlington transistors, each of which can handle high voltage and current. Each unit has an open collector output and a common emitter. These devices include inductive load suppression diodes to increase their efficiency.

The ULN2803A allows direct operation with TTL or CMOS at supply voltages of 5.0 V or 3.3 V since it contains a series base resistor for each Darlington pair. Several interface needs, such as those for relays, solenoids, lamps, tiny motors, and LEDs, can be met by the ULN2803A. By parallelizing the outputs, it will be possible to accommodate applications that call for sink currents larger than a single output can manage.

Feature Description

The ULN2803A utilizes Darlington bridges to couple the NPN transistors in each channel. This setup mimics a single-transistor circuit at extremely high current gains (2). At certain amounts of current, this can reach 10,000 A/A. Strong output current driving at very low input current is made possible by the very high, which allows for low GPIO voltage operating. The GPIO voltage is transformed into base current by the 2.7 k resistor connected between the input and base of the pre-driver NPN Darlington transistor.

A pull-down resistor, measuring 7.2 k, is connected to the base of each NPN, while an input leakage resistor, measuring 3.0 k, is connected to the emitter. While the NPN drivers are off, the kick-back voltage from an inductive load is reduced by the diodes connected between the output and the COM pin (stop sinking). With enough stored energy, the kick-back diode can direct the current in the other direction back into the coil supply. The standard operating condition for diodes involves a reverse bias between the base and collector pins and the emitter. If these diodes are forward-biased, the current drawn by internal parasitic NPN transistors from other (nearby) device pins will be nearly the same.

Device Functional Modes

● Inductive Load Drive

The inherent freewheeling diodes of the ULN2803A allow it to operate inductive loads while simultaneously suppressing kick-back voltage when the COM pin is connected to the coil supply voltage.

Powered by a Resistive Load It is necessary to use a pull-up resistor in series with the ULN2803A when driving a resistive load to get a logic high state. For these uses, you can leave the COM pin unconnected.

Application Information

In most cases, ULN2803A will be used to convert the output of a microcontroller (MCU) or logic device that cannot handle high voltage and/or current to a level where it may safely drive a high-current or high-voltage peripheral. The ULN2803A is frequently used in the following circuit for driving inductive loads. Mechanics like motors, solenoids, and relays fall under this category.


● Layout Guidelines

Due to the low current logic commonly used to operate ULN2803A, thin traces can be utilized on the input. This allows for greater flexibility in the design. To prevent cross-talk, careful attention must be paid to separating the input channels to the greatest feasible extent. It is advised that thick traces be used for the output to drive high currents if required in any capacity. The trace material’s current density and the intended driving current are two factors that can be used to calculate the thickness of the wire. Because the currents from all channels eventually converge on a single emitter, the ideal width for that trace is quite broad. Some applications call for an output current of up to 2.5 A.


In conclusion, the ULN2803AN is a highly powerful and adaptable Darlington transistor array that can easily handle high-voltage and high-current loads. These loads can be difficult to manage with other types of transistor arrays. Its eight NPN Darlington pairs, common-cathode clamp diodes, and collector-current rating of 500 mA make it a good choice for various applications, such as relay, lamp, and motor drivers. It’s rating for collector current is also 500 mA. Because it is compatible with various logic and contains a series base resistor for each Darlington pair, it is simple to use with any MCU or logic device you may already possess.

But don’t just take our word for it; the ULN2803AN is a fantastic alternative for projects that require low GPIO voltages because of its strong current gain and low input current requirements. The ULN2803AN is a tool that can assist you in completing your project, regardless of whether you are a professional or a hobbyist. Why hold off then? Contact ICRFQ, your trusted electronic component distributor in China, to get started today and experience the power of the ULN2803AN for yourself.

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