PC817 Optocoupler: Pinout, Features, Equivalent, and Applications Explained

PC817 Optocoupler: Introduction

The PC817 optocoupler is one of the most widely used isolation components in electronic circuits, designed to safely transfer signals between two electrically isolated sections. It contains an internal infrared LED and a phototransistor, both housed inside a compact 4-pin DIP package. When the LED is forward-biased, it emits infrared light that activates the phototransistor, enabling signal transmission without any direct electrical connection. This ensures excellent protection for microcontrollers, sensors, and logic circuits from high-voltage transients, electrical noise, and ground loop disturbances.

The PC817 is popular for its reliability, low cost, and wide availability. It features a high current transfer ratio (CTR), making it suitable for low-power interfacing applications. Common uses include AC mains sensing, power supply feedback, relay isolation, and digital signal switching. Because of its compact size and stable performance, it is also widely used in SMPS circuits, automation systems, and home appliances. The device operates efficiently over a broad temperature range and provides robust noise immunity, making it ideal for industrial and consumer electronics. Overall, the PC817 is a versatile optocoupler perfect for circuits requiring safe electrical isolation and clean signal transfer.

PC817 Pinout

Pin	Name	Description
1	Anode	Positive terminal of IR LED
2	Cathode	Negative terminal of IR LED
3	Emitter	Emitter of phototransistor
4	Collector	Collector of phototransistor