PC817: Overview,Specifications,Main uses,Features,application fields,working principle and alternative models

PC817 Overview:

The PC817 is a low-input current, high-gain, phototransistor optocoupler integrated circuit. It serves as an optical coupler that consists of an infrared LED and a phototransistor encapsulated within the same package. This component is widely used to isolate and couple electrical signals between two circuits through optical means. Here is a detailed introduction covering the overview, specifications, main uses, features, application fields, working principle, and alternative models of the PC817 optocoupler:



  • Type: Optocoupler (Phototransistor Output)
  • Isolation Voltage: Typically over 5000Vrms
  • Forward Current (IF): Varies depending on model (e.g., PC817 - 50mA max)
  • Collector-Emitter Voltage (VCEO): Typically around 80V
  • Operating Temperature: -30°C to +100°C
  • Package: Available in various packages like DIP-4, SOIC-4, etc.
  • DataSheet PC817X PDF

Main Uses:

  • Signal Isolation: Used to electrically isolate two circuits while transferring signals optically.
  • Noise Suppression: Helps in reducing electromagnetic interference between interconnected circuits.
  • Voltage Level Shifting: Enables signal translation between circuits with different voltage levels.
  • Switching Applications: Employed in applications requiring optically controlled switching.


  • High Isolation Voltage: Offers high isolation voltage levels for safety and noise immunity.
  • Compact Size: Available in small packages suitable for space-constrained designs.
  • Low Power Consumption: Operates at low input current levels for energy efficiency.
  • Fast Response Time: Provides quick response for signal transfer between circuits.
  • Phototransistor Output: Phototransistor output stage for enhanced sensitivity.

Application Fields:

  • Switching Power Supplies: Used for feedback and control signals in power electronics.
  • Industrial Automation: Employed in control and monitoring circuits for safety and isolation.
  • Telecommunications: Utilized in interface circuits for signal transmission and protection.
  • Audio Equipment: Integrated in audio circuits for signal isolation and noise reduction.

Working Principle:

  • When a current flows through the internal LED of the PC817, it emits infrared light.
  • The phototransistor, which is optically coupled to the LED, conducts when exposed to this light, allowing the transfer of signals.
  • This optical coupling provides electrical isolation between the input and output sides of the device.

Alternative Models:

  • PC827: Similar optocoupler with varying specifications and features.
  • PC837: Another optocoupler variant with different characteristics.
  • 4N25: Equivalent optocoupler widely used in similar applications.


  • PC817 optocouplers are versatile components commonly used for signal isolation and noise suppression in various electronic circuits.
  • When selecting an alternative model, ensure compatibility with voltage, current, and other specifications required by your application.

The PC817 optocoupler is a reliable and commonly used component in electronics, offering high isolation voltage, compact size, and low power consumption. It finds applications in signal isolation, noise suppression, voltage level shifting, and switching circuits across industries such as power electronics, industrial automation, telecommunications, and audio equipment.

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