4N28 Optocoupler Phototransistor IC DIP 8 Package

4N28 Optocoupler Phototransistor IC DIP 8 Package

The 4N28 is a widely used phototransistor-based optocoupler designed to provide safe and reliable electrical isolation between an input control signal and an output circuit. It consists of a gallium arsenide infrared LED optically coupled to a silicon NPN phototransistor. This optical coupling allows signal transmission without any direct electrical connection, protecting low-voltage circuits from high-voltage transients, surges, or noise.

The DIP-8 package offers enhanced functionality compared to standard DIP-6 versions, as it includes additional pins for the phototransistor base, enabling users to adjust sensitivity, speed, or noise performance through external components. The wide pin spacing and through-hole design make it highly suitable for industrial PCB designs, prototyping, and applications requiring high isolation distances.

The 4N28 operates with good stability, moderate Current Transfer Ratio (CTR), and supports safe output voltages suitable for both analog and digital isolation tasks. It is commonly used in switching, sensing, and control circuits where robust galvanic isolation is needed.

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Features:-

• Isolation test voltage 5000 VRMS
• Interfaces with common logic families
• Input-output coupling capacitance < 0.5 pF
• Industry standard dual-in-line 6 pin package
• Compliant to RoHS directive 2002/95/EC and in accordance to WEEE 2002/96/EC

Applications

• Switching power supplies (SMPS)
• Industrial control and automation systems
• Relay and TRIAC driver circuits
• Motor control signal isolation
• PLC and microcontroller signal interfacing
• Sensor isolation and noise filtering
• High-voltage to low-voltage signal transmission
• Battery management and protection circuits

4N2 Series Datasheet