H24B2 Optoisolator Equivalent & Substitute Parts

Part Overview

The H24B2 is an optoisolator with Darlington output manufactured by onsemi, rated for 5300Vrms isolation voltage in a 4-DIP through-hole package. This component is classified as obsolete, making identification of functionally equivalent alternatives necessary for ongoing system support and new design implementations. The H24B2 provides single-channel isolation with 400% minimum current transfer ratio and 100mA output current capability, suitable for applications requiring high-voltage galvanic isolation with Darlington switching characteristics.

Key Parameters

Parameter	H24B2 Specification
Manufacturer	onsemi
Product Status	Obsolete
Number of Channels	1
Voltage - Isolation	5300Vrms
Current Transfer Ratio (Min)	400% @ 5mA
Output Type	Darlington
Voltage - Output (Max)	30V
Current - Output / Channel	100mA
Operating Temperature Range	-55°C ~ 85°C
Package / Case	4-DIP (0.300", 7.62mm)
Mounting Type	Through Hole
RoHS Status	RoHS non-compliant

Substitute Part Grouping Explanation

Substitution of the H24B2 requires evaluation against the following critical parameters: isolation voltage rating, current transfer ratio, output current capability, package form factor, and operating temperature range. The 4N46 substitute part is classified as a partial functional equivalent with design trade-offs.

The 4N46 maintains single-channel Darlington output isolation architecture but operates at reduced isolation voltage (3750Vrms versus 5300Vrms). Current transfer ratio performance differs significantly, with the 4N46 offering 200% minimum at 10mA input versus the H24B2's 400% minimum at 5mA. Output current is reduced to 60mA maximum compared to the H24B2's 100mA capability. Package form factor differs: the 4N46 uses 6-DIP versus the H24B2's 4-DIP configuration, requiring PCB layout modification. Operating temperature range is narrower on the 4N46 (-40°C to 85°C versus -55°C to 85°C).

Substitution is permissible only in applications where the reduced isolation voltage, lower current transfer ratio, reduced output current, and narrower temperature range do not compromise system requirements.

Parameter Comparison

Parameter	H24B2 (onsemi)	4N46 (Broadcom Limited)	Compatibility Notes
Number of Channels	1	1	Matched
Voltage - Isolation	5300Vrms	3750Vrms	H24B2 rated higher; 4N46 suitable only for ≤3750Vrms applications
Current Transfer Ratio (Min)	400% @ 5mA	200% @ 10mA	H24B2 provides superior gain; 4N46 requires higher input current for equivalent output
Output Type	Darlington	Darlington with Base	4N46 includes base connection for additional circuit flexibility
Voltage - Output (Max)	30V	20V	H24B2 rated higher; 4N46 suitable only for ≤20V applications
Current - Output / Channel	100mA	60mA	H24B2 provides higher output current; 4N46 limited to 60mA maximum
Operating Temperature Range	-55°C ~ 85°C	-40°C ~ 85°C	H24B2 rated for lower temperatures; 4N46 unsuitable for applications below -40°C
Package / Case	4-DIP (0.300", 7.62mm)	6-DIP (0.300", 7.62mm)	Different pin counts; PCB layout modification required
Mounting Type	Through Hole	Through Hole	Matched
RoHS Status	RoHS non-compliant	RoHS non-compliant	Matched

Engineering Selection Recommendations

The H24B2 is classified as obsolete. For applications currently using the H24B2, component selection must prioritize system-level requirements against available alternatives.

The 4N46 is an active product manufactured by Broadcom Limited with current inventory availability. Selection of the 4N46 as a substitute is permissible only when all of the following conditions are satisfied:

System isolation voltage requirement does not exceed 3750Vrms
System output voltage requirement does not exceed 20V
System output current requirement does not exceed 60mA
System operating temperature range does not extend below -40°C
PCB layout can accommodate 6-DIP package configuration and associated pin reassignment
Input current drive capability can support 10mA minimum input current at the specified current transfer ratio

Both components are RoHS non-compliant and carry identical REACH and ECCN classifications, presenting no differential compliance impact.

Frequently Asked Questions (FAQ)

Q: Can the 4N46 directly replace the H24B2 without PCB modification?

A: No. The H24B2 uses 4-DIP packaging while the 4N46 uses 6-DIP packaging. Pin count and pinout differ, requiring PCB layout modification and schematic redesign.

Q: What is the primary limitation of using the 4N46 as a substitute?

A: The 4N46 operates at 3750Vrms isolation voltage compared to the H24B2's 5300Vrms rating. Applications requiring isolation voltage above 3750Vrms cannot use the 4N46.

Q: Does the 4N46 provide equivalent current transfer ratio performance?

A: No. The 4N46 minimum current transfer ratio is 200% at 10mA input, while the H24B2 provides 400% at 5mA input. The 4N46 requires higher input current to achieve comparable output performance.

Q: Are there temperature range restrictions when substituting with the 4N46?

A: Yes. The 4N46 operating range is -40°C to 85°C, while the H24B2 extends to -55°C. Applications requiring operation below -40°C cannot use the 4N46.

Q: What is the significance of the base connection on the 4N46?

A: The 4N46 includes a base terminal on the Darlington output stage, providing additional circuit design flexibility for applications requiring base current control or active output management. The H24B2 does not include this terminal.

Q: Are both components subject to the same regulatory classifications?

A: Yes. Both the H24B2 and 4N46 are RoHS non-compliant, REACH Unaffected, and classified under ECCN EAR99 with identical HTSUS codes.

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