The 4N35 optocoupler (optoislator) chip can be obtained from a number of online retailers for a very inexpensive price. The 4N35 is a 6-pin IC. Its pinout is. These families include the 4N35/ 4N36/ 4N37/ . Collector-base breakdown voltage1). IC = µA, IB = µA. 4N BVCBO. V. 4N Voltage 30V Feature Phototransistor Optocouples Isolation Voltage (RMS) Vrms CTRmin % t (ON) / t (OFF), us 3us/3us. IF max 60mA. IC max mA.

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So these are all the pin connections. By electrical isolation, we mean that the power going into the input has no effect whatsoever on the power on the output. Without these 4n3 powered, the output side cannot turn on, because the phototransistor needs infrared IR light in order to conduct. So if the power to the input is changed, this does not affect the power on the output, and vice versa. In this project, we will show how to connect an optocoupler chip to a circuit.

How to Build an Optocoupler Circuit

And how it works is we give enough power to the anode and cathode pins, so that the LED is sufficient power to turn on. A lot of optocoupler chips do not even have a terminal for the base because it’s unnecessary to connect it.

Its pinout is shown below. An optocoupler or optoisolator chip is a chip that allows for electrical isolation between the input of the circuit and the output of the circuit. This is a just basic circuit showing how to connect up a photocoupler IC. When switched on, the phototransistor receives IR light and conducts.

4N35 Optocouplers Phototransistor 30V IC

We aren’t going to use any very high voltages. And now there is isolation between the input and output of the circuit. And this is how an optocoupler circuit works. On the output side, being there is electrical isolation, we need to place a power source so that the load, in this case, an LED can turn on. It’s going to be very simple. The third pin is left unconnected. The first 2 pins are the anode and the iv. When off, the phototransistor cannot conduct.


With this setup, there’s no direct id path from the input to the output of the circuit. With infrared, the phototransistor can conduct across from collector to emitter and power on any load connected to the output, which in this case is a LED.

A toggle switch was placed on the input side of the optocoupler circuit in order to switch on and off the circuit.

IC 4N35 Optocoupler

A rundown of all the pin connections is shown in the table below. Optocouplers can also be used if the input power may bring in a lot of uc, which for many applications can be very undesirable.

Electrical isolation can be very important, especially in circuits where the input power to the circuit is very high and there are other parts in the circuit that only require a very small amount of power.

The chip we will use is the popular 4N35 optocoupler chip. I 4N35 is a 6-pin IC. We will show how to wire id chip up to any circuit so that you can obtain electrical isolation as needed.

And we leave the base terminal of the phototransistor unconnected. And this controls the entire circuit. The 4m35 sources are isolated, so they are completely independent. The 4N35 optocoupler optoislator chip can be obtained from a number of online retailers for a very inexpensive price.


So if there is an incident such as a surge of power into the input of the circuit, it doesn’t affect the area that only requires a small amount of power, since it’s isolated from the input. So we connect a 3V power supply source to the collector and this powers on the LED.

Being that there’s no direct conductive pathway, the input and output aren’t linked, so there’s electrical isolation. This would be the main application and use for optoisolators. To see the real-life circuit of it below, id the video below. We connect the output and the voltage necessary to power the output to the collector terminal. But after, you’ll know how to wire up 4j35 type of photocoupler IC.

How to Build an Optocoupler Circuit In this project, we will show how to connect an optocoupler chip to a circuit. Optocoupler Circuit The optocoupler circuit we will build with a 4N35 chip is shown below. Lc, without the IR LED being on, the phototransistor will be in nonconduction move and no current can flow through the phototransistor, meaning anything connected to output will not be powered.

To separate this noise from being induced into the output, electrical isolation is necessary and solves the problem.

This above circuit built on a breadboard is shown below. Once on, it beams 4j35 light onto the phototransistor. We connect the emitter terminal to ground.