4N25 Optocoupler: Pinout, Circuit and Datasheet

The 4N25 series is industry standard single channel phototransistor coupler. This series includes the 4N25, 4N26, 4N27, 4N28. 

Each optocoupler consists of gallium arsenide infrared LED and a silicon NPN phototransistor. 

It contains a light emitting diode optically coupled to a photo-transistor and is packaged in a 6-pin DIP pack- age and available in wide-lead spacing option and lead bend SMD option.

Symbol

Footprint

3D Model

1.IR LED Forward Voltage for turning ON: 1.25V-1.5V (Typically 1.3V, 1.5V being absolute  maximum forward voltage)

2.IR LED Forward Current during ON: 10mA - 60mA (Typically 10mA, 60mA being absolute maximum forward current)

3.IR LED Reverse Voltage Maximum: 5V

4.IR LED Reverse Current Maximum: 100uA

5.Maximum voltage across COLLECTOR and EMITTER of TRANSISTOR: 70V

6.Maximum current allowed trough TRANSISTOR COLLECTOR: 100mA

7.Typical Rise Time: 2us

8.Typical Fall Time: 2us

9.No additional power needed to be applied for chip for making it work.

10.Isolation test voltage 5000 VRMS

11.Interfaces with common logic families

12.Input-output coupling capacitance < 0.5 pF

13.Industry standard dual-in-line 6 pin package

14.Compliant to RoHS directive 2002/95/EC and in accordance to WEEE 2002/96/EC

Vishay Semiconductor Opto Division 4N25 technical specifications, attributes, parameters and parts with similar specifications to Vishay Semiconductor Opto Division 4N25.

4N25 OPTOCOUPLER IC has two components integrated in it. One is INFRARED DIODE and another of INFRARED PHOTOTRANSISTOR. The IR DIODE is connected between terminals 1 and 2, the PHOTOTRANSISTOR is connected at terminals 4, 5 and 6.The internal setup of two components can be seen below. The IR radiation emitted by IR LED will not be visible outside the chip. The whole issue of radiation will be working under background.

For understanding the OPTOCOUPLER we will consider a circuit shown below.

We will get the +3.3Voltage pulses from a microcontroller and these are driven to the POSITIVE of IR DIODE. When IR DIODE gets powered it will emit Infrared rays internally, when these rays fell on the PHOTOTRANSISTOR the transistor gets turned ON. When transistor gets tuned ON the current flows through load circuit and the voltage will be seen across the motor. Thus the motor rotates when microcontroller circuit provides HIGH logic to the 4N25 chip.

When the controller output goes LOW, the IR DIODE input goes LOW. With that the IR DIODE stops emitting radiation internally.  Since radiation is cutoff the PHOTOTRANSISTOR gets turned OFF since the radiation acts as BASE TRIGGER. So its LOW RESISTANCE state to HIGH RESISTANCE states. With HIGH RESISTANCE the complete supply voltage appears across the transistor and current flow in the load circuit gets ZERO. So the motor stops rotating. Thus the motor stops rotating when the microcontroller input to 4N25 gets LOW.

In this circuit you can see the motor draws power from the +12V battery source and not from the controller circuit. The PHOTOTRANSISTOR side secondary circuit here is in complete isolation with the CONTROLLER-PHTODIODE primary circuit. The resistors here are placed for limiting the currents in the circuit. Make a note the resistance values changed depending on voltages.

● DC motor speed control

● Lighting systems

● PWM applications

● AC mains detection

● Reed relay driving

● Switch mode power supply feedback

● Telephone ring detection

● Logic ground isolation

● Logic coupling with high frequency noise rejection

Vishay Intertechnology, Inc. is an American manufacturer of discrete semiconductors and passive electronic components founded by Polish-born businessman Felix Zandman. Vishay has manufacturing plants in Israel, Asia, Europe, and the Americas where it produces rectifiers, diodes, MOSFETs, optoelectronics, selected integrated circuits, resistors, capacitors, and inductors.Vishay is one of the world's foremost manufacturers of power MOSFETs.They have a wide range of power electronic applications, including portable information appliances, internet communications infrastructure, power integrated circuits, cell phones, and notebook computers.

Download datasheets and manufacturer documentation for Vishay Semiconductor Opto Division 4N25.