Introduction

In electronics, where connectivity and isolation are paramount, the 4N35 optocoupler IC stands as a beacon of reliability and versatility. This small yet mighty device is crucial in ensuring signal integrity and safety across a wide range of applications. In this article, we delve into the intricacies of the 4N35 optocoupler IC, exploring its datasheet, pinout, circuit diagram, and diverse uses.

What is Optocoupler IC 4N35?

The 4N35 is a versatile optocoupler, also known as an optical isolator or photocoupler, available in both 6-pin DIP and SMD packages. This device comprises two main components: an infrared LED and a phototransistor. Its operation is straightforward: when the IR LED is powered, the phototransistor detects IR light, leading to transistor saturation or conduction. The internal phototransistor has two bases, one of which can be controlled, facilitating either photodetection or IR light detection, while the other is connected to pin 6 of the device, enabling simultaneous control through both processes.

The maximum collector-emitter voltage of the phototransistor is 30V, with a maximum collector-emitter current of 150mA. However, the collector-emitter saturation voltage ranges from 0.14 to 0.3V. Typically, transistor saturation voltage is around 0.6 or 0.7 volts, but 0.3 volts is the ideal saturation voltage for applications requiring low voltage saturation. As for the IR LED characteristics, the maximum forward current is 60 milliamperes, with a maximum power dissipation of 120 milliwatts. Pin 3 is labeled "NC," indicating can not connected to the internal circuitry.

Figure1-Optocoupler IC 4N35

4N35 Pinout

Figure2-4N35 Pinout

4N35 Pinout Configuration

The IC comes as a dual inline package and has 6 pins. The table below can be referred to understand the pin configuration of the IC.

4N35 Specification

4N35 Features

1. Number of Channels: 1 Channel
2. Maximum Collector-Emitter Voltage: 30V
3. Forward Current: 100mA
4. Forward Voltage: 1.5V
5. Reverse Voltage: 6V
6. Isolation Voltage: 5300 Vrms
7. Operating Temperature: -55 to 100 Degrees C
8. Power dissipation: 250 mW

4N35 Equivalent

4N36、4N37、4N25、4N26、4N28 、PC816、PC817、4N27、4N36 and H11Ax series.

4N35 Schematic and Functional Diagram

Figure3-4N35 Schematic and Functional Diagram

Where to Use the 4N35 Optocoupler?

The 4N35 optocoupler finds application in various requirements within electronic circuits. For instance, it can be employed to safeguard circuits, ICs, and other components from voltage surges or spikes that could potentially damage them. Additionally, it serves isolation purposes within electronic circuits. It can also be utilized to detect voltages in both AC and DC circuits at the output of microcontroller chips and control high-power transistors, and high-voltage equipment.

How to use Optocoupler IC 4N35?

Using the 4N35 optocoupler is straightforward. The device comprises two main components: the IRLED and the phototransistor. The anode pin of the LED can connect to the output of the device you are interfacing with (such as any IC or microcontroller), while the cathode pin of the LED should connect to the ground. The LED should be handled in the same manner as any other LED, including the use of current-limiting resistors.

When the output of the 4N35 goes high, the LED will turn on, and the phototransistor will detect infrared light, causing it to saturate or turn on. Consequently, the collector and emitter pins will short, resulting in the connection of any wires connected to pins 4 and 5.

Figure 4- How to use Optocoupler IC 4N35?

How to operate safely in circuits for long periods?

To ensure the long-term stability and optimal performance of this device, it is advised that users refrain from operating the device beyond its maximum rated values. Avoid imposing or operating loads exceeding 150mA through this device. It is always recommended to use current-limiting resistors in conjunction with the IR LED. Operating the device at temperatures above -55 degrees Celsius and below +100 degrees Celsius is not recommended, while storage should be maintained within temperatures above -55 degrees Celsius and below +150 degrees Celsius.

4N35 Application

Detection of AC power

Driving reed relays

Feedback in switch mode power supplies

Detection of phone ring signals

Isolation of logic ground

Coupling logic with a function to suppress high-frequency noise

2D Model and Dimensions

Figure5-2D Model and Dimensions