4N35 is an optocoupler integrated circuit in which an infrared emitter diode drives a phototransistor. They are also known as optoisolators since they separate two circuits optically.

An optocoupler is analogous to a relay which isolates two circuits magnetically.

A 4N35 is used to interface microcontrollers to parallel port or other circuits that may potentially damage the microcontroller or Arduino such as sensing AC voltages, Zero crossing sensing or Triac interface.

Features

• Isolation test voltage 5000 VRMS
• Interfaces with common logic families
• Input-output coupling capacitance < 0.5 pF
• Industry standard dual-in-line 6 pin package