IRF840 N-Channel MOSFET 500V 8A Equivalent & Substitute Parts

Part Overview

The IRF840 is an N-Channel Metal Oxide Semiconductor Field Effect Transistor (MOSFET) rated for 500V drain-to-source voltage with 8A continuous drain current at 25°C. The device is housed in a Through Hole TO-220AB package and dissipates up to 125W at the case temperature. The IRF840 is classified as obsolete, making equivalent and substitute parts necessary for new designs and ongoing production requirements. Active alternatives with identical or comparable electrical characteristics are available from multiple manufacturers.

Key Parameters

Parameter	Value	Unit
FET Type	N-Channel	—
Technology	MOSFET (Metal Oxide)	—
Drain to Source Voltage (Vdss)	500	V
Continuous Drain Current (Id) @ 25°C	8	A (Tc)
Drive Voltage (Max Rds On)	10	V
Rds On (Max) @ Id, Vgs	850	mOhm @ 4.8A, 10V
Gate Threshold Voltage Vgs(th) (Max) @ Id	4	V @ 250µA
Gate Charge (Qg) (Max) @ Vgs	63	nC @ 10V
Power Dissipation (Max)	125	W (Tc)
Operating Temperature Range	-55 to 150	°C (TJ)
Mounting Type	Through Hole	—
Package / Case	TO-220-3	—

Substitute Part Grouping Explanation

Substitution of the IRF840 is determined by strict equivalence across the following critical parameters:

Primary Substitution Criteria:

Drain to Source Voltage (Vdss): 500V minimum
FET Type: N-Channel
Technology: MOSFET (Metal Oxide)
Mounting Type: Through Hole
Package / Case: TO-220-3 or TO-220AB

Secondary Compatibility Parameters:

Continuous Drain Current (Id) @ 25°C: 8A or greater
Drive Voltage (Max Rds On): 10V
Gate Threshold Voltage Vgs(th): 4V or less
Operating Temperature Range: -55°C to 150°C minimum
Power Dissipation: 125W or greater

Substitute parts are classified into two categories:

Direct Equivalents: Parts with identical electrical specifications and active product status (IRF840PBF, IRF840PBF-BE3).

Parametric Equivalents: Parts meeting or exceeding all critical electrical parameters with comparable or superior performance characteristics (FDP7N50, STP8NM50N, STP9NK50Z).

Parameter Comparison

Parameter	IRF840	IRF840PBF	IRF840PBF-BE3	FDP7N50	STP8NM50N	STP9NK50Z
Manufacturer	Vishay Siliconix	Vishay Siliconix	Vishay Siliconix	onsemi	STMicroelectronics	STMicroelectronics
Product Status	Obsolete	Active	Active	Obsolete	Active	Active
Vdss (V)	500	500	500	500	500	500
Id @ 25°C (A)	8	8	8	7	5	7.2
Rds On (Max) @ 10V (mOhm)	850 @ 4.8A	850 @ 4.8A	850 @ 4.8A	900 @ 3.5A	790 @ 2.5A	850 @ 3.6A
Vgs(th) (Max) (V)	4 @ 250µA	4 @ 250µA	4 @ 250µA	5 @ 250µA	4 @ 250µA	4.5 @ 100µA
Gate Charge Qg (Max) (nC)	63 @ 10V	63 @ 10V	63 @ 10V	16.6 @ 10V	14 @ 10V	32 @ 10V
Power Dissipation (Max) (W)	125	125	125	89	45	110
Operating Temperature (°C)	-55 to 150	-55 to 150	-55 to 150	-55 to 150	to 150	-55 to 150
Package / Case	TO-220-3	TO-220-3	TO-220-3	TO-220-3	TO-220-3	TO-220-3
RoHS Status	Non-compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Affected	Vendor Undefined	REACH Unaffected	REACH Unaffected	REACH Unaffected

Engineering Selection Recommendations

Direct Replacement (Preferred for Pin-Compatible Applications):

IRF840PBF and IRF840PBF-BE3 are direct electrical and mechanical equivalents of the IRF840. Both parts are manufactured by Vishay Siliconix and maintain identical electrical specifications including 500V Vdss, 8A continuous drain current, 850mOhm Rds On, and 125W power dissipation. Both are ROHS3 compliant and carry active product status, ensuring long-term availability. IRF840PBF is available in higher inventory (329,719 pcs) compared to IRF840PBF-BE3 (4,235 pcs). These parts are suitable for direct substitution in all applications where the IRF840 was originally specified.

Parametric Alternatives (For Applications Tolerant of Performance Variations):

STP9NK50Z (STMicroelectronics) provides the closest parametric match among alternative manufacturers. It meets the 500V Vdss requirement, delivers 7.2A continuous drain current (within 90% of IRF840 specification), maintains 850mOhm Rds On at comparable gate drive conditions, and dissipates 110W (88% of IRF840 rating). The part is ROHS3 compliant, carries active product status, and is available in high inventory (15,942 pcs). Operating temperature range is -55°C to 150°C, matching the IRF840 specification.

FDP7N50 (onsemi) is classified as obsolete and delivers 7A continuous drain current with 89W power dissipation. While meeting the 500V Vdss requirement, the reduced current rating (87.5% of IRF840) and power dissipation (71% of IRF840) limit its suitability to applications with lower current demands.

STP8NM50N (STMicroelectronics) is rated for 5A continuous drain current and 45W power dissipation. This part is suitable only for applications requiring significantly reduced current handling and thermal performance compared to the IRF840 specification.

Compliance Considerations:

The IRF840 is RoHS non-compliant. All substitute parts (IRF840PBF, IRF840PBF-BE3, FDP7N50, STP8NM50N, STP9NK50Z) are ROHS3 compliant, meeting current environmental regulations. Applications subject to REACH compliance requirements should prioritize IRF840PBF, FDP7N50, or STP9NK50Z, which carry REACH Unaffected or REACH Affected status with defined supplier accountability.

Frequently Asked Questions (FAQ)

Q: Can IRF840PBF be used as a direct replacement for IRF840?

A: Yes. IRF840PBF is a direct electrical and mechanical equivalent manufactured by Vishay Siliconix. It maintains identical specifications for Vdss (500V), Id (8A), Rds On (850mOhm @ 10V), gate threshold voltage (4V), and power dissipation (125W). The primary difference is product status: IRF840PBF is active, while IRF840 is obsolete. Pinout and TO-220-3 package dimensions are identical, enabling direct PCB substitution.

Q: What is the difference between IRF840PBF and IRF840PBF-BE3?

A: Both parts are manufactured by Vishay Siliconix and share identical electrical specifications. The primary differences are packaging (both supplied in Tube) and REACH compliance status. IRF840PBF carries REACH Affected status with defined supplier accountability. IRF840PBF-BE3 carries Vendor Undefined REACH status. Inventory availability differs: IRF840PBF (329,719 pcs) versus IRF840PBF-BE3 (4,235 pcs). Electrical performance and thermal characteristics are identical.

Q: Is STP9NK50Z a suitable replacement for the IRF840?

A: STP9NK50Z is a parametric equivalent suitable for applications where the IRF840 continuous drain current specification can be reduced from 8A to 7.2A. The part meets the 500V Vdss requirement, maintains comparable Rds On (850mOhm @ 10V), and provides 110W power dissipation (88% of IRF840 rating). Operating temperature range (-55°C to 150°C) matches the IRF840. STP9NK50Z is ROHS3 compliant and carries active product status with high inventory availability (15,942 pcs). Applications operating at or below 7.2A continuous drain current can use this part without performance degradation.

Q: Why is the IRF840 obsolete, and what are the long-term availability implications?

A: The IRF840 is classified as obsolete by Vishay Siliconix. Obsolete status indicates the manufacturer has discontinued active production and support. Current inventory (7,026 pcs) represents remaining stock. Direct equivalents IRF840PBF and IRF840PBF-BE3 are active products with significantly higher inventory levels, ensuring long-term availability. For new designs and production planning, direct equivalents or parametric alternatives are recommended to avoid supply chain disruption.

Q: What are the package compatibility requirements for substitution?

A: All substitute parts listed maintain the TO-220-3 package / case designation and Through Hole mounting type. Physical dimensions and pinout are compatible across IRF840, IRF840PBF, IRF840PBF-BE3, FDP7N50, STP8NM50N, and STP9NK50Z. Direct PCB substitution is possible without layout modifications. Thermal performance may vary due to differences in power dissipation ratings; thermal management design should account for the specific power dissipation of the selected substitute part.

Q: Are there current rating limitations when using STP8NM50N or FDP7N50?

A: Yes. STP8NM50N is rated for 5A continuous drain current (62.5% of IRF840 specification) and 45W power dissipation (36% of IRF840 rating). FDP7N50 is rated for 7A continuous drain current (87.5% of IRF840 specification) and 89W power dissipation (71% of IRF840 rating). These parts are suitable only for applications where the actual operating current is within their rated limits. Applications requiring the full 8A continuous drain current capability of the IRF840 must use IRF840PBF, IRF840PBF-BE3, or STP9NK50Z.

Q: What compliance certifications should be considered when selecting a substitute?

A: The IRF840 is RoHS non-compliant. All substitute parts are ROHS3 compliant, meeting current environmental regulations for new designs and production. REACH compliance status varies: IRF840PBF, FDP7N50, and STP9NK50Z carry REACH Unaffected status; IRF840PBF-BE3 carries Vendor Undefined status. Applications subject to REACH compliance requirements should prioritize parts with defined REACH status. All parts carry EAR99 ECCN classification and 8541.29.0095 HTSUS code.

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