Optocoupler 4N25

The 4N25 Optocoupler is a 6-pin phototransistor-based isolation device designed to transfer signals between two electrically isolated circuits. It provides safe and reliable signal isolation, making it ideal for microcontroller interfaces, power electronics, and industrial control applications. The internal infrared LED and phototransistor allow the input and output to be completely separated, protecting sensitive components from high voltages, noise, and ground loops.

Features

• High isolation between input and output

• Infrared LED + Phototransistor configuration

• Fast switching response suitable for digital interfaces

• Low power LED input

• Improves safety by protecting low-voltage circuits

• Compatible with microcontrollers such as Arduino, PIC, AVR, STM32

• Ideal for signal level shifting and noise isolation

Specifications

• Model: 4N25

• Package: 6-pin DIP

• Isolation Voltage: 5000V RMS (typical)

• Input LED Forward Voltage: ~1.2V

• Input Current: 10–20mA typical

• Output Type: NPN Phototransistor

• CTR (Current Transfer Ratio): 20%–50% (depending on model)

• Operating Temperature: -55°C to +100°C

• Applications:

  • Power supply feedback circuits

  • Microcontroller signal isolation

  • Switching power supplies

  • Triac/Thyristor triggering

  • Industrial control systems