3N251 Bridge Rectifier Single Phase 800V 1.5A - Equivalent & Substitute Parts

Part Overview

The 3N251 is a single-phase bridge rectifier manufactured by onsemi, rated for 800V peak reverse voltage and 1.5A average rectified current in a through-hole KBPM package. This component is classified as obsolete, making equivalent substitute parts necessary for new designs and ongoing production requirements. Substitute parts must maintain compatibility across voltage rating, current capacity, mounting type, and thermal operating range to ensure functional equivalence in circuit applications.

Key Parameters

Parameter	3N251 Specification
Diode Type	Single Phase
Technology	Standard
Voltage - Peak Reverse (Max)	800 V
Current - Average Rectified (Io)	1.5 A
Voltage - Forward (Vf) (Max) @ If	1 V @ 1 A
Current - Reverse Leakage @ Vr	5 µA @ 800 V
Operating Temperature Range	-55°C ~ 165°C (TJ)
Mounting Type	Through Hole
Package / Case	4-SIP, KBPM
Moisture Sensitivity Level (MSL)	1 (Unlimited)
Product Status	Obsolete

Substitute Part Grouping Explanation

Substitute parts for the 3N251 are evaluated based on the following critical parameters that determine functional equivalence:

Primary Substitution Criteria:

Voltage - Peak Reverse (Max): Must equal or exceed 800 V
Current - Average Rectified (Io): Must equal or exceed 1.5 A
Diode Type: Must be Single Phase
Technology: Must be Standard
Mounting Type: Must be Through Hole
Operating Temperature Range: Must accommodate the application's thermal requirements

Secondary Compatibility Factors:

Forward voltage characteristics at rated current
Reverse leakage current specifications
Package mechanical compatibility with circuit board layout
Moisture sensitivity and environmental ratings

Parts are grouped into two categories based on current rating alignment:

Group 1 - Direct Current Match (1.5A): KBP08G maintains the exact 1.5A current rating with 800V voltage specification, providing the closest electrical equivalence.

Group 2 - Higher Current Rating (2.0A): KBP208G, VS-2KBP02, VS-2KBP04, VS-2KBP06, VS-2KBP08, and VS-2KBP10 offer 2.0A current capacity, suitable for applications where the 3N251's 1.5A rating is marginal or where design margin is required. These parts vary in voltage rating from 200V to 1000V.

Parameter Comparison

Parameter	3N251	KBP08G	KBP208G	VS-2KBP02	VS-2KBP04	VS-2KBP06	VS-2KBP08	VS-2KBP10
Manufacturer	onsemi	Diodes Incorporated	SMC Diode Solutions	Vishay	Vishay	Vishay	Vishay	Vishay
Diode Type	Single Phase	Single Phase	Single Phase	Single Phase	Single Phase	Single Phase	Single Phase	Single Phase
Technology	Standard	Standard	Standard	Standard	Standard	Standard	Standard	Standard
Voltage - Peak Reverse (Max)	800 V	800 V	800 V	200 V	400 V	600 V	800 V	1000 V
Current - Average Rectified (Io)	1.5 A	1.5 A	2 A	2 A	2 A	2 A	2 A	2 A
Voltage - Forward (Vf) (Max) @ If	1 V @ 1 A	1.1 V @ 1.5 A	1.1 V @ 2 A	1 V @ 1 A	1 V @ 1 A	1 V @ 1 A	1 V @ 1 A	1 V @ 1 A
Current - Reverse Leakage @ Vr	5 µA @ 800 V	5 µA @ 800 V	5 µA @ 800 V	10 µA @ 200 V	10 µA @ 400 V	10 µA @ 600 V	10 µA @ 800 V	10 µA @ 1000 V
Operating Temperature Range	-55°C ~ 165°C	-65°C ~ 150°C	-55°C ~ 150°C	-40°C ~ 150°C	-40°C ~ 150°C	-40°C ~ 150°C	-40°C ~ 150°C	-40°C ~ 150°C
Mounting Type	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole	Through Hole
Package / Case	4-SIP, KBPM	4-SIP, KBP	4-ESIP	4-SIP, D-44	4-SIP, D-44	4-SIP, D-44	4-SIP, D-44	4-SIP, D-44
Product Status	Obsolete	Active	Active	Active	Active	Active	Active	Active
RoHS Status	Not specified	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Unaffected	REACH Affected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

Primary Substitute - KBP08G (Diodes Incorporated): KBP08G is the optimal substitute for the 3N251, matching the 800V voltage rating and 1.5A current specification exactly. The part is active in production with ROHS3 compliance and REACH unaffected status. Package compatibility requires verification as KBP08G uses 4-SIP KBP package versus the original KBPM package; mechanical footprint differences may require PCB layout adjustment. Operating temperature range of -65°C to 150°C covers the lower end of the 3N251 specification but may be insufficient for applications requiring the full -55°C to 165°C range.

Secondary Substitute - VS-2KBP08 (Vishay General Semiconductor - Diodes Division): VS-2KBP08 provides 800V voltage rating with 2.0A current capacity, offering design margin above the 1.5A requirement. Active product status with ROHS3 compliance and REACH unaffected designation. Package uses 4-SIP D-44 format, requiring PCB layout verification. Operating temperature range of -40°C to 150°C is narrower than the 3N251 specification. Higher current rating suits applications where thermal or transient margin is critical.

Voltage-Specific Alternatives: For applications where 800V rating is not mandatory, VS-2KBP06 (600V, 2A) and VS-2KBP04 (400V, 2A) provide active alternatives with Vishay manufacturing and ROHS3 compliance. Selection depends on actual circuit voltage requirements. VS-2KBP10 (1000V, 2A) is suitable for designs requiring voltage headroom above 800V.

Compliance Considerations: All active substitute parts carry ROHS3 compliance. KBP208G is the only substitute with REACH affected status; applications subject to REACH restrictions should prioritize KBP08G, VS-2KBP series, or other REACH unaffected alternatives.

Frequently Asked Questions (FAQ)

Q: Can KBP08G directly replace the 3N251 without PCB modifications? A: KBP08G matches the electrical specifications (800V, 1.5A) but uses a different package format (4-SIP KBP versus KBPM). Physical pin spacing and lead configuration must be verified against the original PCB layout. Package compatibility assessment is required before implementation.

Q: Why do some substitutes have higher current ratings (2A instead of 1.5A)? A: Higher current-rated parts (KBP208G, VS-2KBP series) provide design margin and thermal headroom for applications where the 1.5A rating is marginal. These parts are electrically compatible when the circuit current requirement does not exceed 1.5A, as the bridge rectifier will operate within its rated envelope.

Q: What is the impact of different operating temperature ranges? A: The 3N251 operates from -55°C to 165°C. KBP08G (-65°C to 150°C) and VS-2KBP series (-40°C to 150°C) have narrower upper temperature limits. Applications requiring operation above 150°C junction temperature cannot use these substitutes. Verify thermal design requirements before selection.

Q: Are all substitute parts RoHS compliant? A: All active substitute parts listed are ROHS3 compliant. The original 3N251 RoHS status is not specified due to its obsolete classification. For new designs, all listed substitutes meet current RoHS requirements.

Q: Does package format affect electrical performance? A: Package format (KBPM, KBP, D-44, 4-ESIP) does not affect electrical performance but determines mechanical compatibility with PCB layouts. Lead spacing, mounting hole diameter, and thermal dissipation characteristics vary by package. Physical verification is required for board-level integration.

Q: Which substitute offers the best long-term availability? A: All listed substitutes carry active product status. KBP08G (Diodes Incorporated) and VS-2KBP08 (Vishay) are from established manufacturers with broad distribution networks. Inventory levels at time of procurement should be verified with component suppliers.

Q: Can VS-2KBP10 (1000V) be used in place of the 3N251 (800V)? A: Yes. VS-2KBP10 exceeds the voltage requirement and provides 2A current capacity. Higher voltage rating does not degrade performance in 800V applications; the part will operate within its rated envelope. This option is suitable when voltage margin is desired for circuit protection.

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