4N35 Optocoupler IC

4N35 Optocoupler IC 

The 4N35 is a widely-used optocoupler (opto-isolator) that provides electrical isolation between an input (low-voltage control side) and an output (high-voltage or noisy side). It consists of an infrared LED and a phototransistor packaged together but electrically isolated. When current flows through the LED, it emits infrared light that activates the phototransistor, allowing signal transfer without direct electrical connection.

It is commonly used for signal isolation, noise protection, and interfacing microcontrollers with high-voltage circuits.

Click here to view the related products

Key Features

• Integrated IR LED and phototransistor
• High isolation voltage: typically 5 kV RMS
• CTR (Current Transfer Ratio): 100% to 320% (depending on model)
• Compact 6-pin DIP package
• Low input LED current required
• Fast switching for general digital applications
• Wide operating temperature range
• Provides protection from high voltages and surges

Pin Configuration (6-Pin DIP)

• Anode (LED +)
• Cathode (LED -)
• NC
• Emitter (Transistor E)
• Collector (Transistor C)
• Base (optional control)

Electrical Characteristics (Typical)

• Forward current (LED): 10–20 mA
• Forward voltage: ~1.2 V
• Collector-emitter voltage (max): 70 V
• Collector current: up to 50 mA
• CTR: varies with model and input current

Applications

• Microcontroller–to–high-voltage interface
• AC mains isolation
• Switch-mode power supplies (SMPS)
• Noise suppression and protection
• Industrial automation
• Triac driver circuits
• On/Off control for motors, relays, LEDs
• Isolation in communication lines
• Feedback control in power converters