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Photosensor (for opto-isolator) Component – Computer, Electronic and Optical Product Manufacturing

Component Specifications

Definition

A photosensor is a semiconductor-based electronic component designed to detect and convert light signals into electrical signals. In opto-isolator applications, it serves as the receiver element, typically paired with an infrared LED emitter. When light from the emitter strikes the photosensor, it generates a photocurrent that modulates the output circuit, enabling signal transmission while maintaining complete electrical isolation between input and output sides. This component is critical for noise reduction, voltage level shifting, and protection against voltage spikes in industrial control systems.

Working Principle

The photosensor operates on the photoelectric effect, where incident photons (typically infrared light from an LED) excite electrons in the semiconductor material (commonly silicon-based phototransistors or photodiodes). This generates a photocurrent proportional to the light intensity. In opto-isolators, this current is amplified to drive the output circuit, creating an electrically isolated replica of the input signal. Key parameters include response time, spectral sensitivity (centered around 850-950 nm for IR), and current transfer ratio (CTR).

Materials

Semiconductor substrate: Silicon (Si) for photodiodes/phototransistors; Encapsulation: Epoxy resin or silicone for optical coupling and protection; Lead frame: Copper alloy with tin plating; Optical window: Clear epoxy or glass for light transmission.

Technical Parameters

Dark Current 10-100 nA
Package Type DIP-4, DIP-6, SOP-4
Response Time 3-20 μs
Isolation Voltage 2500-5000 Vrms
Spectral Sensitivity 850-950 nm (Infrared)
Operating Temperature -40°C to +100°C
Current Transfer Ratio (CTR) 20-600%

Standards

ISO 9001, IEC 60747-5-5, JEDEC JESD22

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Photosensor (for opto-isolator).

Parent Products

This component is used in the following industrial products

Opto-isolator / Relay

An electronic component that provides electrical isolation and signal switching between circuits in I/O modules.

View Product Details

Engineering Analysis

Risks & Mitigation

CTR degradation over time due to LED aging
Contamination of optical path reducing sensitivity
Thermal runaway in high-temperature environments
ESD damage during handling
Misalignment during assembly causing signal loss

FMEA Triads

Trigger: LED emitter degradation in opto-isolator
Failure: Decreased CTR leading to signal loss
Mitigation: Use components with matched aging characteristics; implement periodic CTR testing; design circuits with 30-50% CTR margin

Trigger: Moisture ingress into package
Failure: Internal condensation scattering light, reducing sensitivity
Mitigation: Select epoxy-encapsulated components with IP67 equivalent sealing; control humidity in storage/assembly

Trigger: Excessive operating temperature
Failure: Thermal damage to semiconductor junction
Mitigation: Adhere to temperature specifications; add heat sinking if needed; monitor ambient temperature in enclosure

Industrial Ecosystem

Compatible With

Interchangeable Parts

Compliance & Inspection

Tolerance

CTR: ±20% typical batch variation; Response time: ±15%; Isolation voltage: +0/-10% test tolerance

Test Method

IEC 60747-5-5 for optoelectronic isolation; JEDEC JESD22 for environmental reliability; In-circuit CTR measurement at 5mA/5V; Hi-pot testing at 1.2x rated isolation voltage

Procurement Evaluation Criteria

Not customer reviews or live demand data. These dimensions support RFQ preparation and supplier evaluation.

Technical documentation

4/5

Manufacturing capability

4/5

Inspection readiness

5/5

Supplier transparency

3/5

These scores are example evaluation dimensions, not real customer ratings, country-specific buyer feedback, or live inquiry activity.

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Frequently Asked Questions

What is the difference between a phototransistor and photodiode photosensor in opto-isolators?

Phototransistors provide higher gain and sensitivity but slower response (10-20 μs), ideal for DC/low-frequency signals. Photodiodes offer faster response (1-5 μs) but lower output, suitable for high-speed digital applications. Selection depends on speed vs. sensitivity requirements.

How does temperature affect photosensor performance in industrial environments?

Temperature impacts CTR (typically decreasing by 0.5%/°C above 25°C) and dark current (doubling every 10°C rise). Industrial-grade components use temperature-compensated designs and wide operating ranges (-40°C to +100°C) for stability.

Can photosensors be replaced without recalibrating the opto-isolator system?

Generally yes if specifications match, particularly CTR, response time, and package. However, batch variations may require minor circuit adjustments. Always verify compatibility with manufacturer datasheets.

Can I contact factories directly?

Yes, each factory profile provides direct contact information.

Data Basis

CNFX manufacturer profiles, technical classification, publicly available product information, and ongoing plausibility checks.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Photosensor (for opto-isolator)