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Дома > Other > 4N35 Optocoupler IC: Datasheet, Pinout, Circuit Diagram & Uses

4N35 Optocoupler IC: Datasheet, Pinout, Circuit Diagram & Uses

Время обновления: 2024-02-02 14:41:20


As we delve into the intricate realm of electronic components, one crucial player takes center stage – the Optocoupler IC. In the ever-evolving landscape of technology, understanding the fundamental aspects of Optocoupler ICs becomes imperative. These electronic devices, characterized by their ingenious design, serve a pivotal role in ensuring the seamless functioning of electronic circuits. In this exploration, we embark on a journey to unravel the definition and purpose of Optocoupler ICs, shedding light on their significance within the intricate tapestry of electronic circuits. In this article, we'll delve into the 4N35 Optocoupler IC, including its circuit diagram, pinout, datasheet, uses and more details, uncover the crucial role this component plays, not only in connecting different parts of a circuit but also in maintaining the integrity and reliability of electronic systems.

What is IC 4N35?

The IC 4N35 serves as a versatile optocoupler with applications across various fields. It comprises a light-emitting diode optically linked to a phototransistor. Its composition includes a gallium arsenide infrared LED and a silicon NPN phototransistor. Upon applying the input signal to the LED at the input terminal, the LED illuminates. Subsequently, the light receiver converts the received light signal into an electrical signal, which is then output directly or after amplification to a standard digital level. This completes the transition and transmission of electricity-light-electricity. Since light serves as the transmission medium, the input and output terminals are electrically isolated, a process known as electrical isolation. Encased in a 6-pin DIP package, it offers wide lead spacing options and lead bending SMD options. Typically, it boasts a response time of 3 µs, and the minimum Current Transfer Ratio (CTR) at an input current of 10 mA is 100%.

IC 4N35.jpg

4N35 Pinout

The IC 4N35 is presented in a dual inline package with a total of 6 pins. Refer to the table below for a comprehensive understanding of the pin configuration:


IC 4N35 Pin Configuration

Pin NumberPin TypePin Description
3NCNot Connected

Features of 4N35

  • Isolation test voltage of 5000 VRMS

  • Compatible with general logic series

  • Input-output coupling capacitance less than 0.5 pF

  • Dual in-line 6-pin package following industry standards

  • Conforms to RoHS Directive 2002/95/EC and complies with WEEE 2002/96/EC

4N35 Specifications

Number of Channels1--
Isolation Voltage3550 Vrms1 minuteUL1577 standard
Collector-Emitter Voltage (Vce)30V-
Emitter-Collector Breakdown Voltage (Bveco)60V-
Collector Current (Ic)50mADC
Forward Current (If)100mA-
Forward Voltage (Vf)1.5V-
Peak Forward Current Surge (Ifsm)1.5A10μs pulse
Collector Dark Current (Icbo)100nAVce = 20V
Collector-Emitter Leakage Current (Ice)10μAVce = 20V, If = 0mA
Current Transfer Ratio (CTR)50% min-If = 10mA
Rise Time (tr)10μs-
Fall Time (tf)15μs-
Operating Temperature Range (TA)-40 to +100°C-
Storage Temperature Range (TSTG)-55 to +125°C-
Package6-pin DIP--

4N35 Schematic

4N35 Schematic.png

4N35 Functional Diagram

4N35 Functional Diagram.png

How Does the Optocoupler IC Work?

The optocoupler IC comprises a gallium arsenide infrared LED and a silicon NPN phototransistor, making it user-friendly. The base pin (pin 6) is not required to use the IC as a phototransistor. The suggested circuit below guides the design of your circuit using the optocoupler IC.


EL4N35-Working 2.png

Connect the anode (pin 1) and cathode (pin 2) pins of the infrared LEDs to the logic input and ground, respectively. Pull up the collector pin (pin 5) using a resistor and connect the output device to the other end. In this case, an output probe is connected to monitor the output. Ground the emitter pin (pin 4).

Note: Ensure that the emitter and the cathode pin are not connected to the same ground, as they are meant to be isolated.

Working: When a logic 0 input is applied to the IR LED, the LED remains OFF, not triggering the transistor, and the output received is HIGH across the collector-emitter terminal. Conversely, when the LED receives a logic 1, it turns on, triggering the transistor and shorting the collector-emitter junction, resulting in a 0 at the output.

Note: The Collector-emitter voltage can be set up to a maximum of 30V.

How to Use 4N35?

Step 1: Components

Step 2: Principle:

The 4N35 is an optocoupler designed for general applications. It comprises a gallium arsenide infrared LED and a silicon NPN phototransistor.

The purpose of an optocoupler is to break the connection between the signal source and the signal receiver, preventing electrical interference. In other words, it is used to shield against interference from external electrical signals. The 4N35 can be employed in AV conversion audio circuits and finds widespread use in electrical isolation for general optocouplers.

Refer to the internal structure of the 4N35 above. Pins 1 and 2 are connected to the infrared LED. When the LED is powered, it emits infrared light. To prevent LED burnout, a resistor (approximately 1K) is typically connected to pin 1. Then, when the phototransistor receives the radiation, it opens the circuit. This can be used to control the load connected to the phototransistor. Even in the case of a load short circuit, it won't affect the control board, ensuring effective electrical isolation.

Step 3: Schematic:

4N35 Schematic.png

Step 4: Procedure:

In this experiment, the LED is used as a load connected to the NPN phototransistor. Connect pin 2 of the 4N35 to pin 7 of the control board and connect pin 1 to a 1K current-limiting resistor, then to 5V. Connect pin 4 to Uno's GND, and pin 5 to the cathode of the LED. Then, use a 220-ohm resistor to connect the anode of the LED to 5V. During programming, when pin 7 is at a low level, the infrared LED emits infrared light. The phototransistor then receives the infrared light and becomes energized, making the LED cathode low, thereby turning on the LED. Similarly, you can control the LED by grounding pin 2, making it light up.

  • Step 1:

Build the circuit.

  • Step 2:

Download Arduino.

  • Step 3:

Upload the code to the Arduino Uno board.

Click the "Upload" icon to upload the code to the control board.

If "Done uploading" appears at the bottom of the window, the sketch has been successfully uploaded.

  • Step 4: Code:


Code analysis.png

// Turn on a led by


// turn on the LED

for half a second, then off for half a second, repeatedly



int OptoPin = 7;

// attach the input of the 4n35 to pin 7

void setup() {

pinMode(OptoPin, OUTPUT); // set it as OUTPUT


void loop() {

digitalWrite(OptoPin, LOW); // set the OptoPin as LOW level, then the led

connected on the output of 4n35 will be light


// delay 500ms

digitalWrite(OptoPin, HIGH); // turn off the led


// delay 500ms


4N35 Alternatives/Equivalents

MCT2E, PC817, and 6N137 can be equivalent to 4N35.

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


The 4N35 Optocoupler has modern electronics. Its ability to facilitate electrical isolation, protect sensitive components, and enhance the overall reliability of electronic systems is unparalleled. In an era where electronic devices are omnipresent, the 4N35 stands as a silent sentinel, ensuring the smooth and secure transmission of signals.

Read More

Предыдущий: PC817 IC Optocoupler Pinout, Circuit, Datasheet, and Uses

Следующий: The Ultimate Guide to IR2104 Half Bridge MOSFET Driver


  • What does a 4N35 IC do?
  • The 4N35 interrupts the connection between the signal source and signal receiver, effectively halting electrical interference.

  • What is the maximum input current of the otocoupler 4N35?
  • 100mA.

  • What is the difference between PC817 and 4N35?
  • The PC817 belongs to the category of phototransistor optocouplers, whereas the 4N35 is categorized as a photo-triac optocoupler. Phototransistor devices are predominantly employed in DC circuits, while photo-triac devices enable the control of AC-powered circuits.

  • Can 4N25 be replaced with 4N35?
  • The 4N35 is identified as a substitute for the 4N25.

  • What is an optocoupler used for?
  • Optocouplers offer isolation between circuits with low and high voltages.

  • When should I use the optocoupler?
  • Use the optocoupler when isolation is required between the relay coil circuit, including its power supply, and the input control components.

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