EL817(B) Optoisolator Equivalent & Substitute Parts

Part Overview

The EL817(B) is a single-channel optoisolator with transistor output manufactured by Everlight Electronics Co Ltd. This component provides 5000Vrms isolation voltage and is designed for DC input applications requiring galvanic isolation in 4-DIP through-hole packages. The part is currently in active production status with 54,000 units in stock. Substitute parts are necessary to address supply chain flexibility, alternative sourcing options, and design optimization across different current transfer ratio grades and output voltage specifications.

Key Parameters

Parameter	Value
Isolation Voltage	5000Vrms
Number of Channels	1
Output Type	Transistor
Input Type	DC
Current Transfer Ratio (Min)	130% @ 5mA
Current Transfer Ratio (Max)	260% @ 5mA
Maximum Output Voltage	35V
Output Current per Channel	50mA
Rise / Fall Time	4µs / 3µs
Operating Temperature Range	-55°C to 110°C
Package Type	4-DIP (0.300", 7.62mm)
Mounting Type	Through Hole
RoHS Status	ROHS3 Compliant

Substitute Part Grouping Explanation

Substitute parts for the EL817(B) are classified into two categories based on electrical parameter compatibility:

Direct Substitutes (Identical CTR Range): Parts with matching current transfer ratio specifications (130% to 260% @ 5mA) that maintain identical electrical performance characteristics. These include FOD817B300 (onsemi), 140817140210 (Würth Elektronik), and Q817B (QT Brightek).

Parametric Equivalents (Alternative CTR Grades): Parts with different current transfer ratio ranges but identical isolation voltage, output type, input type, package configuration, and operating temperature range. These include FOD817A300 (80-160% CTR), FOD817C300 (200-400% CTR), FOD817300 (50-600% CTR), and FOD817D300 (300-600% CTR) from Fairchild Semiconductor and onsemi.

Critical Substitution Parameters:

Isolation voltage: 5000Vrms (all substitutes match)
Package: 4-DIP through-hole (all substitutes match)
Output type: Transistor (all substitutes match)
Input type: DC (all substitutes match)
Operating temperature: -55°C to 110°C (all substitutes match)
Output current capacity: 50mA per channel (all substitutes match)
Vce saturation: 200mV maximum (all substitutes match)

Variable Parameters Affecting Selection:

Current transfer ratio grade (determines switching speed and input current requirements)
Maximum output voltage (35V for EL817(B) vs. 70V for FOD817 series)
Forward voltage drop (1.2V to 1.24V across all parts)
Rise/fall time specifications (3-4µs typical across all parts)

Parameter Comparison

Part Number	Manufacturer	CTR Min @ 5mA	CTR Max @ 5mA	Vout Max	Vf Typ	If Max	Rise/Fall Time	Inventory	RoHS3
EL817(B)	Everlight Electronics	130%	260%	35V	1.2V	60mA	4µs / 3µs	54,000	Yes
FOD817B300	onsemi	130%	260%	70V	1.2V	50mA	4µs / 3µs	35,100	Yes
FOD817C300	onsemi	200%	400%	70V	1.2V	50mA	4µs / 3µs	32,088	Yes
FOD817A300	onsemi	80%	160%	70V	1.2V	50mA	4µs / 3µs	56,300	Yes
FOD817300	Fairchild Semiconductor	50%	600%	70V	1.2V	50mA	4µs / 3µs	12,560	Not specified
FOD817D300	Fairchild Semiconductor	300%	600%	70V	1.2V	50mA	4µs / 3µs	8,580	Not specified
140817140210	Würth Elektronik	130%	260%	35V	1.24V	60mA	3µs / 4µs	1,093	Yes
Q817B	QT Brightek	130%	260%	35V	1.24V	60mA	6µs / 8µs	1,717	Yes

Engineering Selection Recommendations

For Direct Replacement (Identical Electrical Performance):

FOD817B300 from onsemi is the primary direct substitute. It maintains the 130-260% current transfer ratio specification of the EL817(B) while offering higher maximum output voltage (70V vs. 35V). This part is ROHS3 compliant, has 35,100 units in inventory, and is in active production status. The higher output voltage rating provides additional design margin without affecting applications limited to 35V operation.

For Higher Current Transfer Ratio Applications:

FOD817C300 (onsemi) provides 200-400% CTR specification, suitable for applications requiring faster switching response or lower input current drive. This part maintains all other electrical parameters and is ROHS3 compliant with 32,088 units available.

For Lower Current Transfer Ratio Applications:

FOD817A300 (onsemi) provides 80-160% CTR specification for applications requiring higher input current or specific circuit impedance matching. This part is ROHS3 compliant with the highest inventory level (56,300 units) among onsemi FOD817 variants.

For Extreme CTR Range Flexibility:

FOD817300 (Fairchild Semiconductor) spans 50-600% CTR, accommodating the widest range of input current and switching speed requirements. However, RoHS3 compliance status is not specified for this part.

For Output Voltage Limited to 35V:

140817140210 (Würth Elektronik) and Q817B (QT Brightek) maintain the 35V maximum output voltage specification identical to EL817(B). Both are ROHS3 compliant. The 140817140210 has lower inventory (1,093 units) but maintains identical CTR and forward voltage specifications. Q817B has slightly slower rise/fall times (6µs/8µs vs. 4µs/3µs) and lower inventory (1,717 units).

Compliance Considerations:

All recommended direct substitutes (FOD817B300, FOD817C300, FOD817A300, 140817140210, Q817B) are ROHS3 compliant. Fairchild Semiconductor FOD817 variants do not specify RoHS3 compliance status in provided documentation.

Frequently Asked Questions (FAQ)

Q: Can FOD817B300 replace EL817(B) in all applications?

A: FOD817B300 is electrically compatible as a direct substitute. Both parts share identical current transfer ratio (130-260% @ 5mA), isolation voltage (5000Vrms), output current capacity (50mA), and operating temperature range (-55°C to 110°C). The higher maximum output voltage of FOD817B300 (70V vs. 35V) does not create incompatibility in circuits designed for 35V operation. Both are through-hole 4-DIP packages with identical pinout.

Q: What is the difference between CTR grades (FOD817A300, FOD817B300, FOD817C300)?

A: Current Transfer Ratio (CTR) determines the relationship between input LED current and output transistor current. FOD817A300 (80-160% CTR) requires higher input current for a given output current. FOD817B300 (130-260% CTR) matches EL817(B) specifications. FOD817C300 (200-400% CTR) requires lower input current for the same output. Selection depends on circuit input current availability and switching speed requirements. All three maintain identical isolation voltage, package, and operating temperature specifications.

Q: Are there inventory or lead time advantages to using substitute parts?

A: FOD817A300 has the highest inventory among onsemi variants (56,300 units). FOD817B300 has 35,100 units. EL817(B) has 54,000 units. Würth Elektronik 140817140210 and QT Brightek Q817B have significantly lower inventory (1,093 and 1,717 units respectively), making them less suitable for high-volume applications requiring consistent supply.

Q: Can I use FOD817300 or FOD817D300 from Fairchild Semiconductor?

A: These parts are parametric equivalents with wider CTR ranges (50-600% and 300-600% respectively). They maintain all critical electrical parameters: 5000Vrms isolation, 4-DIP package, 50mA output current, and -55°C to 110°C operating temperature. However, RoHS3 compliance status is not specified in available documentation. Verify compliance requirements before selection for regulated applications.

Q: What is the impact of rise/fall time differences?

A: EL817(B) specifies 4µs rise time and 3µs fall time. Most FOD817 variants match these specifications. Q817B has slower times (6µs rise, 8µs fall), which may affect maximum switching frequency in high-speed applications. For applications operating below 100 kHz, this difference is typically not significant. For applications above 200 kHz, verify timing requirements against specific part specifications.

Q: Are all substitutes available in tube packaging like EL817(B)?

A: EL817(B) is supplied in tube packaging. FOD817B300, FOD817C300, FOD817A300, 140817140210, and Q817B are all available in tube packaging. FOD817300 and FOD817D300 from Fairchild Semiconductor are supplied in bulk packaging, which may affect handling and storage requirements.

Q: What is the forward voltage difference between 1.2V and 1.24V?

A: EL817(B) and most FOD817 variants specify 1.2V typical forward voltage. 140817140210 and Q817B specify 1.24V. This 0.04V difference is negligible in most circuit designs and does not affect substitutability. Both values fall within standard LED forward voltage tolerances.

Q: Can I mix different CTR grades in the same circuit board?

A: Yes, different CTR grades can coexist in the same design if circuit sections have different input current availability or switching speed requirements. However, for consistency in production and troubleshooting, using a single part number across identical circuit functions is recommended.

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