4N35 is a commonly used optoisolator (also called an optocoupler) in electronics. It allows electrical signals to pass between two isolated circuits using light, which provides galvanic isolation.
Specifications
Input (LED) forward voltage: ~1.2 V
Input forward current: 10–60 mA (max 60 mA)
Output (Phototransistor) Collector–Emitter voltage: 30 V
Output Collector Current: 50 mA max
Current Transfer Ratio (CTR): 50%–600% (depends on LED current and conditions)
Isolation Voltage: ~5000 V RMS between input and output
Response time: ~3 µs (fast enough for many switching applications)
Application
Isolation between microcontroller logic and high‑voltage AC circuits
Switching relays, triacs, or motors
Signal isolation in communication lines
Protecting low-voltage circuits from spikes or noise