When selecting an optocoupler for electronic circuit isolation, the EL817 and PC817 are two popular choices, each offering distinct advantages for specific applications. Both optocouplers provide essential signal isolation between different voltage domains, preventing electrical interference and ensuring safety in various circuits. While they share some similarities, such as their 4-pin DIP packaging and infrared LED coupled to a phototransistor, each model has unique features that make it better suited for particular tasks. 

In this comparison, we will explore the differences between the EL817 and PC817 in terms of their pinout, features, applications, and other factors, helping you determine the best option for your project needs.

What is EL817

The EL817 is an optocoupler consisting of an infrared emitting diode (LED) optically coupled to a phototransistor. Designed for electrical isolation, the EL817 is packaged in a standard 4-pin DIP, available in various configurations, including surface-mount options. Its main purpose is to provide a secure means of transferring electrical signals between two isolated circuits, making it ideal for interfacing microcontrollers with high-voltage AC or DC systems.

How to use EL817

To use the EL817, connect its input side (pins 1 and 2) to the control circuit with a current-limiting resistor for the LED. The output side (pins 3 and 4) is connected to the high-voltage side, typically with the collector tied to a pull-up resistor. This configuration allows the EL817 to switch the output based on the input signal, ensuring electrical isolation while transmitting the control signal effectively.

What is PC817

The PC817 is another optocoupler widely used for signal isolation, featuring an infrared LED coupled to a phototransistor in a 4-pin DIP package. Like the EL817, it ensures safe and noise-free transmission of electrical signals between circuits operating at different voltage levels. The PC817 is renowned for its reliability and compatibility with various industrial and consumer electronics applications.

How to use PC817

To use the PC817, connect its input terminals (anode and cathode) to the control circuit with a resistor to limit the LED current. On the output side, connect the collector to the power supply through a pull-up resistor and the emitter to the ground of the output circuit. This setup allows the PC817 to isolate and transfer control signals between circuits efficiently.

EL817 vs PC817: Pinout

EL817 vs. PC817: Pinout

Both EL817 and PC817 share a similar 4-pin DIP pinout:

• Pin 1 (Anode): Connects to the LED’s positive terminal.
• Pin 2 (Cathode): Connects to the LED’s negative terminal.
• Pin 3 (Emitter): Phototransistor output.
• Pin 4 (Collector): Connects to the high-voltage side via a pull-up resistor

EL817 vs PC817: Features

EL817 Features

Maximum Supply Current: 95µA

Maximum Offset Voltage:

200µV (EL8170)

1000µV (EL8173)

Maximum Input Bias Current: 3nA

Bandwidth (-3dB):

396kHz (Gain = 10)

192kHz (Gain = 100)

Single-Supply Operation:

Input Voltage Range: Rail-to-rail

Output Swing: Rail-to-rail

Compliance: Pb-Free (RoHS Compliant)

PC817 Features

Input Diode Forward Voltage: 1.25V

Maximum Collector-Emitter Voltage: 80V

Maximum Collector Current: 50mA

Cut-off Frequency: 80kHz

Rise Time: 18µs

Fall Time: 18µs

Packaging Options: Available in 4-pin DIP through-hole or SMT package

EL817 vs PC817: Application

EL817 Applications

• Measuring Instruments
• Home Appliances
• Telecommunication Devices
• Programmable Controllers

PC817 Applications

• Electrical Isolation Circuits
• Microcontroller I/O Switching
• Signal Isolation
• Noise Coupling Circuits
• Isolation Between Digital and Analog Circuits
• AC/DC Power Control

EL817 vs PC817: Equivalent

EL817 Equivalent

TLP181

LTV817

K817P

PC817 Equivalent

TLP321

MCT2E

LTV817

EL817 vs PC817: Advantages

EL817 Advantages

• Low Input Current Requirement: Requires minimal current for operation, enhancing energy efficiency.
• High Bandwidth: Offers a -3dB bandwidth up to 396kHz (G=10), making it suitable for high-speed applications.
• Rail-to-Rail Operation: Both input voltage range and output swing support rail-to-rail operation, improving signal fidelity.
• Compact Design: Available in a small package, making it ideal for space-constrained applications.
• RoHS Compliance: Pb-free design adheres to environmental standards.

PC817 Advantages

• Versatile Voltage and Current Ratings: Supports up to 80V collector-emitter voltage and 50mA collector current, making it adaptable to various circuits.
• Reliable Isolation: Designed for robust electrical isolation between input and output.
• Wide Availability: Readily available in through-hole (DIP) and surface-mount (SMT) packages, enhancing compatibility.
• Cost-Effective: Economical choice for basic optocoupler needs in consumer and industrial applications.
• Proven Performance: Trusted in the industry for general-purpose signal isolation and control tasks.

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