Skip to datasheet
Phototransistor optocoupler

PC817 Working Principle

Learn how PC817 works with an illustrated explanation and practical readings.

Package view

PC817 at a glance

Follow the labeled connections and functional stages

PC817 working principle: illustrated functional stages, basic circuit and connections
Select the diagram to read it at full resolution.

How it works

3 stages · Explore one step at a time

Step 1 / 3

Turn current into light

Input current flows from anode to cathode through the internal infrared LED. The resistor limits that current.

Step 2 / 3

Cross the insulating barrier

Photons reach the output transistor. No wire or shared ground is needed across the barrier.

Step 3 / 3

Turn light into an output level

The transistor sinks current from the output pull-up. With the LED off, the pull-up restores a high level; with sufficient drive, the output goes low.

Component view