on November 15th 85

Why Choose the 4N25 Optocoupler for Your Projects

The 4N25 optocoupler is a simple yet effective device that lets you safely transfer signals between circuits without direct electrical contact. In this article, you’ll learn how it works, its features, and where it can be used.

Catalog

Introduction to 4N25 Optocoupler

The 4N25 optocoupler is a widely used device that allows you to connect and control circuits while keeping them electrically isolated. This isolation is achieved using an infrared LED and a phototransistor. When current flows through the LED, it emits light that activates the phototransistor, enabling current to pass in the second circuit. This setup ensures safe communication between circuits that may have different voltage levels, protecting sensitive components from damage.

Packaged in a compact 6-pin DIP design, the 4N25 optocoupler is versatile and reliable. Its design ensures that you can use it in various applications where electrical isolation and precise signal control are necessary. Whether you're working on motor controls, logic circuits, or communication systems, the 4N25 offers a practical solution for bridging circuits effectively.

4N25 Pin Configuration

4N25 CAD Model

4N25 Symbol

4N25 Footprint

4N25 3D Model

Key Features of 4N25

Infrared LED Forward Voltage

The infrared LED inside the 4N25 requires a forward voltage ranging between 1.25V and 1.5V, with 1.3V being the typical value. This means it activates reliably in most circuit designs without needing additional adjustments. The range ensures compatibility with standard voltage levels, simplifying its integration into your projects.

Infrared LED Current Range

The LED operates effectively at a typical current of 10mA but can handle up to 60mA when needed. This range allows the 4N25 to work in low-power and high-power applications, offering versatility for different circuit demands. With proper current-limiting resistors, you can control the LED's input for optimal performance.

Collector-Emitter Voltage

On the phototransistor side, the 4N25 supports a maximum collector-emitter voltage of 70V. This capability allows you to use the device in circuits with higher voltage levels, providing reliable operation without the risk of component failure. It ensures the optocoupler can handle demanding applications where higher voltages are present.

Isolation Voltage

One of the standout features of the 4N25 is its high isolation test voltage of up to 5000 VRMS. This guarantees a safe separation between the input and output sides, protecting your sensitive control circuitry from potential damage caused by high voltages or noise in the secondary circuit.

Fast Switching Time

With a rise time and fall time of about 2µs, the 4N25 is well-suited for high-speed applications. This fast response ensures that your circuits can operate efficiently, especially in systems that require quick signal processing or switching.

Standard Package Design

The 4N25 is housed in a compact 6-pin dual inline package (DIP), which is widely recognized and easy to work with. Its standard design makes it compatible with most circuit boards and sockets, allowing for straightforward installation and replacement if needed.

RoHS Compliance

The 4N25 meets RoHS (Restriction of Hazardous Substances) standards, ensuring it is environmentally friendly and safe to use. This compliance is especially beneficial if you’re working on modern electronics projects that need to meet strict regulatory requirements.

4N25 Specifications

Technical specifications, features, characteristics, and components with comparable specifications of Vishay Semiconductor Opto Division 4N25

Type	Parameter
Factory Lead Time	14 Weeks
Contact Plating	Tin
Mount	PCB, Through Hole
Mounting Type	Through Hole
Package / Case	6-DIP (0.300, 7.62mm)
Number of Pins	6
Supplier Device Package	6-DIP
Collector-Emitter Breakdown Voltage	30V
Current Transfer Ratio-Min	20% @ 10mA
Number of Elements	1
Operating Temperature	-55°C~100°C
Packaging	Tube
Published	2014
Part Status	Active
Moisture Sensitivity Level (MSL)	1 (Unlimited)
Max Operating Temperature	100°C
Min Operating Temperature	-55°C
Max Power Dissipation	150mW
Base Part Number	4N25
Approval Agency	UL, VDE
Voltage - Isolation	5000Vrms
Output Voltage	30V
Output Type	Transistor with Base
Number of Channels	1
Power Dissipation	150mW
Voltage - Forward (Vf) (Typ)	1.3V
Input Type	DC
Forward Current	60mA
Max Output Voltage	30V
Output Current per Channel	50mA
Rise Time	2s
Forward Voltage	1.3V
Fall Time (Typ)	2s
Collector Emitter Voltage (VCEO)	30V
Max Collector Current	100mA
Rise / Fall Time (Typ)	2μs 2μs
Reverse Breakdown Voltage	5V
Max Input Current	60mA
Current - DC Forward (If) (Max)	60mA
Input Current	50mA
Max Junction Temperature (Tj)	125°C
Vce Saturation (Max)	500mV
Current Transfer Ratio	50%
Height	4.8mm
REACH SVHC	Unknown
Radiation Hardening	No
RoHS Status	ROHS3 Compliant
Lead Free	Lead Free

Comparable Alternatives to 4N25

Part Number	Description	Manufacturer
IL55B	Transistor Output Optocoupler, 1-Element, 5300V Isolation	Telefunken Microelectronics Gmbh
SFH601-3-X006	Transistor Output Optocoupler, 1-Element, 5300V Isolation, 0.400 INCH, ROHS COMPLIANT, PLASTIC, DIP-6	Vishay Semiconductors
H11AA	Transistor Output Optocoupler, 1-Element, 5000V Isolation	CT Micro International Corporation
SFH615A-1-X006	Optocoupler - Transistor Output, 1 CHANNEL TRANSISTOR OUTPUT OPTOCOUPLER, DIP-4	Vishay Intertechnologies
SFH6156-4-X001T	Transistor Output Optocoupler, 1-Element, 5300V Isolation	Siemens
ILD615-4-X019	Transistor Output Optocoupler, 2-Element, 5300V Isolation, 0.400 INCH, ROHS COMPLIANT, PLASTIC, DIP-8	Vishay Semiconductors
ILD615-2-X009T	Transistor Output Optocoupler, 2-Element, 5300V Isolation, DIP-8	Infineon Technologies AG
SFH615-4-X001	Transistor Output Optocoupler, 1-Element, 5300V Isolation, DIP-4	Siemens
MCT271-X001	Transistor Output Optocoupler, 1-Element, 5300V Isolation, DIP-6	Siemens
SFH615A	Transistor Output Optocoupler, 1-Element, 5300V Isolation, PLASTIC, DIP-4	Infineon Technologies AG

Using the 4N25 Optocoupler

The 4N25 optocoupler combines two key components: an infrared LED and an infrared phototransistor. The LED is connected to terminals 1 and 2, while the phototransistor is connected to terminals 4, 5, and 6. This internal structure allows the device to transmit signals between circuits without direct electrical contact.

To see how it works, imagine a microcontroller circuit that sends a +3.3V pulse to the LED. When powered, the LED emits infrared light inside the chip, activating the phototransistor. Once the phototransistor is turned on, it allows current to flow in the connected load circuit. For example, this current could power a motor, causing it to rotate.

When the microcontroller output goes low, the LED stops emitting light. Without the infrared light, the phototransistor turns off, cutting off current flow in the load circuit. This process stops the motor.

This design ensures the control circuit remains isolated from the load circuit, which can have different voltage levels. The separation protects the microcontroller and other sensitive components while maintaining efficient operation in various applications like motor controls and logic circuits.

Applications of 4N25

DC Motor Speed Control

The 4N25 plays a significant role in controlling the speed of DC motors by isolating the control circuit from the motor circuit. This isolation ensures that any electrical noise or surges from the motor do not affect the sensitive control system. By adjusting the input signals to the optocoupler, you can fine-tune the motor speed with precision.

Lighting Systems

In lighting systems, the 4N25 allows you to control brightness or on/off switching while keeping the control and load circuits separate. This is particularly useful in dimmer circuits or automated lighting setups, where electrical isolation ensures safety and reliability.

Pulse Width Modulation (PWM) Applications

The 4N25 is widely used in PWM circuits for precise control of power delivered to devices like motors, LEDs, or heaters. Its ability to isolate the microcontroller from the high-power components ensures smooth operation and prevents damage to the control circuitry.

AC Mains Detection

The 4N25 can detect the presence of AC mains voltage in a circuit, making it an ideal choice for monitoring or protection systems. By isolating the sensing circuit from the mains supply, it protects low-voltage components and enhances the overall safety of the system.

Reed Relay Driving

Driving reed relays with the 4N25 allows you to achieve isolated switching. This is especially helpful in circuits where the relay needs to control high-voltage or high-current loads, as it shields the control side from potential interference or damage.

Switch Mode Power Supply Feedback

In switch mode power supplies, the 4N25 serves in feedback loops to regulate output voltage. By transmitting feedback signals while isolating the control circuit, it ensures stable and consistent performance of the power supply. This application is common in devices that require precise voltage control.

Telephone Ring Detection

The 4N25 is used in telephone systems to detect incoming ring signals. It provides the necessary isolation between the telephone line and the control circuit, ensuring that the system operates reliably without the risk of damage from line voltage fluctuations.

Noise Rejection in Logic Coupling

By isolating logic circuits, the 4N25 helps reduce high-frequency noise, improving the reliability of signal processing. This feature is especially useful in environments with significant electrical noise, where clean signal transfer is critical for stable circuit operation. This makes it a preferred choice in industrial control and communication systems.

Packaging Details for 4N25

Manufacturer of 4N25

Vishay Intertechnology, Inc. is the company behind the 4N25 optocoupler. Known for producing high-quality electronic components, Vishay specializes in semiconductors and passive components that serve a wide range of industries. From optoelectronics like the 4N25 to resistors, capacitors, and MOSFETs, their products are designed to perform reliably in demanding environments.