ULN2803 Transistor DIP-18

The ULN2803 is an 8‑channel NPN Darlington transistor array in a DIP‑18 package, designed to interface low‑power logic with higher‑voltage, higher‑current loads. Each channel provides an open‑collector, high‑current sink with built‑in flyback (suppression) diodes for safe driving of inductive loads. Ideal for Arduino, Raspberry Pi, and other microcontroller projects, as well as professional control systems and automation modules.

Key Features 🔍

• Darlington transistor array for high current gain and robust switching
• Eight NPN Darlington pairs with individually addressable channels
• High-current sink: up to 500 mA per channel (observe thermal limits)
• High-voltage outputs: up to 50 V (open-collector)
• Integrated suppression diodes (common cathode to COM pin) for inductive loads 🚦
• TTL/CMOS-compatible inputs for 3.3 V and 5 V logic interfacing
• Open-collector outputs allow flexible pull-up to external supply rails

Technical Specifications 📐

• Package Type: DIP‑18
• Operating Temperature: −20°C to +85°C
• Storage Temperature: −55°C to +150°C
• Channels: 8x NPN Darlington sinks
• Maximum Output (Collector) Voltage: 50 V
• Maximum Sink Current (per channel): 500 mA
• Output Configuration: Open collector, common emitter to GND
• Clamp Diodes: Integrated; connect COM to load supply for inductive kick protection
• Logic Compatibility: TTL/CMOS, suitable for Arduino, Raspberry Pi, and most microcontrollers

Connection Highlights 🧰

• Inputs (1–8): Drive from GPIO or logic outputs
• Outputs (1–8): Open-collector sinks to GND; connect load between supply and output
• COM pin: Tie to positive load supply when driving inductive loads for diode clamping
• GND (Emitters): Connect to system ground

Applications 💡

• Relay drivers
• Hammer drivers
• Lamp drivers
• Display drivers (LED and gas discharge)
• Line drivers
• Logic buffers
• Solenoid and buzzer drivers
• Stepper motor coil drivers

Why Choose ULN2803 for Arduino and Raspberry Pi? 🤖

Bridge low‑power GPIO to higher‑voltage, higher‑current loads safely and efficiently. The ULN2803 protects your microcontroller while simplifying wiring for relays, solenoids, and LED arrays—perfect for rapid prototyping and reliable production designs using popular electronics components and modules.

Usage Notes 🛠️

• Outputs sink current to ground; they do not source current
• For inductive loads, connect COM to the positive load supply to engage the integrated clamp diodes
• Observe per‑channel and total package current/thermal limits for safe operation
• Keep grounds common between logic and load supplies when interfacing with microcontrollers