Photocoupler Assembly

Product Specifications

Technical details and manufacturing context for Photocoupler Assembly

Definition

The Photocoupler Assembly is the packaged functional unit within an Isolation Barrier (Optocoupler/Transformer) system. It comprises the core optocoupler chip (LED and phototransistor/photodiode) housed within a protective casing, along with integrated leads, pins, or terminals for circuit connection. Its primary role is to provide galvanic isolation—transferring electrical signals between two circuits via light, preventing ground loops, noise, and high-voltage hazards—while being a ready-to-install part of a larger isolation module or board.

This assembly is designed for use in computer, electronic, and optical product manufacturing, where it serves as a component for signal isolation. The assembly includes a gallium arsenide (GaAs) LED chip and a silicon phototransistor or photodiode chip, encapsulated in an epoxy molding compound with copper alloy leads for electrical connection. Key parameters, as listed in the directory, include isolation voltage (3750–5000 Vrms per IEC 60747-5-5), current transfer ratio (50–600% at IF=5mA, VCE=5V), collector-emitter saturation voltage (0.1–0.4V at IF=10mA, IC=2mA), input forward voltage (1.2–1.6V at IF=10mA), operating temperature range (-40 to 85°C), storage temperature range (-55 to 125°C), input-output capacitance (0.3–1.0 pF at 1MHz), propagation delay time (2–10 µs at IF=10mA, RL=1kΩ), creepage distance (6–8 mm per IEC 60664-1), clearance distance (5–7 mm per IEC 60664-1), package type (DIP-4 to DIP-8), and weight (0.5–2.0 g). These values are reference ranges and must be verified for the specific model and application.

When selecting a photocoupler assembly, verify the required isolation voltage, current transfer ratio, and switching speed against your circuit design. Confirm the package type and lead configuration for your PCB layout. Always check the manufacturer's datasheet for exact specifications and compliance with relevant standards. The assembly is not a complete isolation system; it must be integrated with other components as part of a larger isolation barrier. For maintenance, monitor for degradation in performance, such as increased propagation delay or reduced CTR, which may indicate aging or damage. Failure boundaries include exceeding maximum ratings, which can lead to breakdown of isolation and potential safety hazards.

Working Principle

An input electrical signal drives an infrared LED inside the assembly, which emits light. This light crosses an internal isolation gap (typically an air gap or transparent dielectric) and strikes a photosensitive semiconductor (e.g., phototransistor, photodiode, or photo-triac). The photosensor converts the light back into an electrical signal at the output, achieving signal transfer without electrical contact between input and output circuits.

Common Materials

Gallium Arsenide (GaAs) LED chip, Silicon phototransistor/photodiode chip, Epoxy molding compound, Copper alloy leads

Technical Parameters

Parameter	Typical range	Notes & selection driver
Isolation Voltage	3750–5000 Vrms	Minimum for reinforced insulation per IEC 60747-5-5.IEC 60747-5-5
Current Transfer Ratio	50–600 %	At IF=5mA, VCE=5V; lower CTR may require higher drive current.IEC 60747-5-5
Collector-Emitter Saturation Voltage	0.1–0.4 V	At IF=10mA, IC=2mA; affects output low level.
Input Forward Voltage	1.2–1.6 V	At IF=10mA; typical for GaAs IR LED.
Operating Temperature Range	-40–85 °C	Extended range may require derating.IEC 60747-5-5
Storage Temperature Range	-55–125 °C	Non-operating condition.IEC 60747-5-5
Input-Output Capacitance	0.3–1.0 pF	At 1MHz; affects high-frequency isolation.
Propagation Delay Time	2–10 µs	At IF=10mA, RL=1kΩ; important for switching speed.
Creepage Distance	6–8 mm	For reinforced insulation in pollution degree 2.IEC 60664-1
Clearance Distance	5–7 mm	Minimum air gap for rated isolation voltage.IEC 60664-1
Package Type	DIP-4–DIP-8	Through-hole or SMD variants available.
Weight	0.5–2.0 g	Depends on package and lead count.

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Infrared LED Die Part
Converts input electrical signal into infrared light.

Material: Gallium Arsenide (GaAs)
Phototransistor Die Part
Detects infrared light and converts it back into an output electrical signal.

Material: Silicon
Molded Package
Provides mechanical protection, electrical insulation, and thermal management for the semiconductor dies.

Material: Epoxy resin
Lead Frame Part
Provides electrical connection points (pins) and structural support within the package.

Material: Copper alloy
Transparent Dielectric Optional
Fills the isolation gap so light passes while the two sides stay electrically apart.

Applied To / Applications

This component is essential for the following industrial systems and equipment:

Isolation Barrier (Optocoupler/Transformer)

View system integration details

Manufacturers of Photocoupler Assembly

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Frequently Asked Questions

What is the primary function of a photocoupler assembly?

The primary function is to provide galvanic isolation between two circuits, transferring signals via light to prevent ground loops, noise, and high-voltage hazards. It is a ready-to-install component for integration into an isolation barrier system.

What are the typical isolation voltage ratings?

According to the directory, the isolation voltage range is 3750–5000 Vrms, referenced to IEC 60747-5-5. However, you must verify the exact rating for the specific model with the manufacturer, as it depends on the design and application.

How do I select the right photocoupler assembly for my application?

Consider the required isolation voltage, current transfer ratio (CTR), propagation delay, package type, and temperature range. Ensure the assembly meets your circuit's electrical and mechanical requirements. Always consult the datasheet and verify compliance with relevant standards.

What are the maintenance signals or failure indicators?

Signs of degradation include increased propagation delay, reduced CTR, or erratic output. These may indicate aging or damage. Exceeding maximum ratings can cause isolation breakdown, to safety hazards. Regular testing and adherence to operating conditions are recommended.

Data Basis

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pressure:	Atmospheric to 1.5 bar
other spec:	Isolation Voltage: 5kV RMS, Data Rate: Up to 10 Mbps
temperature:	-40°C to +125°C

Product Specifications

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Application Fit & Sizing Matrix

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