IRF840S MOSFET N-Channel 500V 8A Equivalent & Substitute Parts

Part Overview

The IRF840S is an N-Channel MOSFET manufactured by Vishay Siliconix, rated for 500V drain-to-source voltage with 8A continuous drain current in a Surface Mount TO-263 (D2PAK) package. This device is classified as obsolete, necessitating identification of equivalent and substitute components for ongoing design support and procurement continuity. The IRF840S serves in high-voltage switching applications requiring reliable performance across industrial and consumer electronics sectors.

Key Parameters

Parameter	Value	Unit
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
Input Capacitance (Ciss) (Max) @ Vds	1300	pF @ 25V
Power Dissipation (Max)	3.1 / 125	W (Ta) / W (Tc)
Operating Temperature Range	-55 to 150	°C (TJ)
Mounting Type	Surface Mount	—
Package / Case	TO-263-3, D2PAK	—
Vgs (Max)	±20	V

Substitute Part Grouping Explanation

Substitution of the IRF840S is determined by electrical and mechanical compatibility across the following critical parameters:

Electrical Compatibility Criteria:

Drain to Source Voltage (Vdss): Substitute must equal or exceed 500V
Continuous Drain Current (Id): Substitute must equal or exceed 8A at 25°C
Gate Drive Voltage: Substitute must operate at 10V drive voltage
Operating Temperature Range: Substitute must span -55°C to 150°C (TJ)
FET Type: N-Channel MOSFET technology required

Mechanical Compatibility Criteria:

Mounting Type: Surface Mount required
Package / Case: TO-263-3 or D2PAK (2 Leads + Tab) footprint required

Compliance Considerations:

RoHS Status: Active substitutes must meet current regulatory requirements
Moisture Sensitivity Level (MSL): Level 1 (Unlimited) preferred for handling consistency

Substitutes are grouped into two categories: direct electrical equivalents and performance-enhanced alternatives that maintain full backward compatibility while offering improved electrical characteristics.

Parameter Comparison

Parameter	IRF840S	IRF840SPBF	STB11NK50ZT4
Manufacturer	Vishay Siliconix	Vishay Siliconix	STMicroelectronics
Product Status	Obsolete	Active	Active
Drain to Source Voltage (Vdss)	500 V	500 V	500 V
Continuous Drain Current (Id) @ 25°C	8 A (Tc)	8 A (Tc)	10 A (Tc)
Drive Voltage (Max Rds On)	10 V	10 V	10 V
Rds On (Max) @ Id, Vgs	850 mOhm @ 4.8A, 10V	850 mOhm @ 4.8A, 10V	520 mOhm @ 4.5A, 10V
Gate Threshold Voltage Vgs(th) (Max) @ Id	4 V @ 250µA	4 V @ 250µA	4.5 V @ 100µA
Gate Charge (Qg) (Max) @ Vgs	63 nC @ 10V	63 nC @ 10V	68 nC @ 10V
Input Capacitance (Ciss) (Max) @ Vds	1300 pF @ 25V	1300 pF @ 25V	1390 pF @ 25V
Power Dissipation (Max)	3.1 W (Ta), 125 W (Tc)	3.1 W (Ta), 125 W (Tc)	125 W (Tc)
Operating Temperature Range	-55°C to 150°C (TJ)	-55°C to 150°C (TJ)	-55°C to 150°C (TJ)
Mounting Type	Surface Mount	Surface Mount	Surface Mount
Package / Case	TO-263-3, D2PAK	TO-263-3, D2PAK	TO-263-3, D2PAK
Vgs (Max)	±20 V	±20 V	±30 V
RoHS Status	Non-compliant	ROHS3 Compliant	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Affected	REACH Unaffected
Moisture Sensitivity Level (MSL)	1 (Unlimited)	1 (Unlimited)	1 (Unlimited)

Engineering Selection Recommendations

IRF840SPBF (Vishay Siliconix)

The IRF840SPBF is an active-status direct electrical equivalent to the IRF840S. It maintains identical electrical specifications including 500V Vdss, 8A continuous drain current, 850mOhm Rds On, and 63nC gate charge. The IRF840SPBF is ROHS3 compliant and REACH affected, meeting current regulatory requirements for new designs. This substitute is recommended for applications requiring exact electrical performance matching with modern compliance certifications. Packaging is supplied in Tube format.

STB11NK50ZT4 (STMicroelectronics)

The STB11NK50ZT4 is an active-status performance-enhanced substitute featuring improved electrical characteristics within the same 500V voltage class. It provides 10A continuous drain current (25% higher than IRF840S), reduced Rds On of 520mOhm (39% lower than IRF840S), and extended gate voltage rating of ±30V (versus ±20V). The STB11NK50ZT4 maintains identical 500V Vdss, 10V drive voltage, and TO-263 D2PAK package compatibility. This device is ROHS3 compliant and REACH unaffected. The STB11NK50ZT4 is suitable for applications where improved thermal performance and higher current handling are beneficial within existing circuit topologies.

Both substitutes maintain identical operating temperature range (-55°C to 150°C TJ), Surface Mount mounting type, and MSL Level 1 handling requirements. Selection between IRF840SPBF and STB11NK50ZT4 depends on whether exact electrical matching or performance enhancement is required for the target application.

Frequently Asked Questions (FAQ)

Q: Can the IRF840SPBF be used as a direct replacement for the IRF840S?

A: Yes. The IRF840SPBF is electrically identical to the IRF840S across all specified parameters including Vdss (500V), Id (8A), Rds On (850mOhm), and gate charge (63nC). Both devices use the same TO-263 D2PAK package. The primary difference is product status (IRF840SPBF is active) and regulatory compliance (IRF840SPBF is ROHS3 compliant). No circuit modifications are required.

Q: What are the advantages of using STB11NK50ZT4 over IRF840SPBF?

A: The STB11NK50ZT4 offers improved electrical performance: 10A continuous drain current versus 8A, and 520mOhm Rds On versus 850mOhm. These improvements reduce power dissipation and thermal stress in switching applications. The STB11NK50ZT4 also provides ±30V gate voltage rating versus ±20V. All three devices share identical 500V Vdss, 10V drive voltage, and TO-263 D2PAK package compatibility.

Q: Are there package compatibility concerns when substituting these parts?

A: No. All three devices (IRF840S, IRF840SPBF, and STB11NK50ZT4) use identical TO-263-3 D2PAK Surface Mount packages with 2 leads plus tab configuration. PCB footprints and thermal management layouts require no modification.

Q: What is the difference between IRF840S and IRF840SPBF regarding compliance?

A: The IRF840S is RoHS non-compliant and REACH unaffected. The IRF840SPBF is ROHS3 compliant and REACH affected. For new designs subject to RoHS regulations, IRF840SPBF or STB11NK50ZT4 are required. For legacy systems or applications without RoHS requirements, IRF840S may remain acceptable if inventory is available.

Q: Can STB11NK50ZT4 be used in circuits designed for IRF840S without modification?

A: Yes. The STB11NK50ZT4 maintains full backward compatibility with IRF840S circuits. It meets or exceeds all electrical specifications: 500V Vdss, 10V drive voltage, and -55°C to 150°C operating range. The improved Rds On (520mOhm versus 850mOhm) and higher current rating (10A versus 8A) provide performance enhancement without requiring circuit redesign. Gate drive circuits operate identically.

Q: What is the moisture sensitivity level for these devices?

A: All three devices (IRF840S, IRF840SPBF, and STB11NK50ZT4) are rated MSL Level 1 (Unlimited). This classification indicates unlimited shelf life without moisture bake-out requirements, simplifying inventory management and procurement logistics.

Q: Which substitute should be selected for new production designs?

A: For new production designs, IRF840SPBF is recommended if exact electrical matching to the original IRF840S specification is required. STB11NK50ZT4 is recommended if improved thermal performance and higher current capability provide system-level benefits. Both are active-status products with current regulatory compliance (ROHS3). Selection depends on whether the application benefits from the STB11NK50ZT4's enhanced specifications or requires exact electrical equivalence.

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