4N33

Overview

The Vishay 4N33 is a general-purpose, single-channel photodarlington optocoupler featuring a gallium arsenide infrared LED and a silicon photodarlington sensor. It provides high isolation with an insulation voltage of 5300 Vrms. The device offers a minimum current transfer ratio (CTR) of 500% at a forward current of 10 mA. Key electrical parameters include a collector-emitter voltage of 30V and a maximum forward current of 60mA. It is housed in a standard 6-pin DIP package.

Feature Summary

• Integrates a gallium arsenide infrared LED with a silicon photodarlington sensor for efficient optical coupling.
• Provides robust electrical isolation between input and output circuits with a high insulation voltage rating.
• Features a Darlington output configuration to achieve high current transfer ratios for sensitive signal detection.

Applications

• General purpose signal isolation in industrial control systems
• Power supply feedback loops for circuit protection
• Interface circuits connecting microprocessors to high-voltage loads

Procurement Notes

Verify component authenticity through authorized distributors as the 4N33 series has been subject to discontinuance notifications by various manufacturers including Vishay. Confirm specific manufacturing lot dates and RoHS compliance status, as legacy stock may vary in environmental specifications. Ensure that the selected supplier provides valid traceability documentation for quality assurance purposes.

Selection Notes

Select this component when high gain is required for low-level signal switching applications. The photodarlington output offers superior sensitivity compared to standard transistor outputs. Consider the slow switching speed inherent to Darlington structures; it is suitable for DC or low-frequency AC signals but not for high-speed data transmission where faster optocouplers are necessary.

Part Context

The 4N33 belongs to a family of general-purpose photodarlington optocouplers widely used in legacy electronic designs. It is often paired with the 4N32, which features a standard phototransistor output instead of a Darlington pair. This family serves as a foundational component for basic galvanic isolation requirements in power electronics and instrumentation.

Replacement Considerations

Public confirmed substitute part numbers include the Fairchild Semiconductor FOD823 and the ON Semiconductor PC123. These alternatives offer similar pin configurations and electrical characteristics, ensuring compatibility in existing PCB layouts without requiring design modifications.

FAQ

What is the typical current transfer ratio range for the 4N33?

The current transfer ratio typically ranges from 50% to 600%, with a minimum guaranteed value of 500% at a forward current of 10 mA in many datasheet specifications.

Is the 4N33 suitable for high-speed digital communication?

No, the 4N33 is not suitable for high-speed applications due to the slow response time associated with the photodarlington output structure. It is designed for low-frequency or DC isolation tasks.