IRF634 N-Channel MOSFET 250V 8A Equivalent & Substitute Parts

Part Overview

The IRF634 is an N-Channel MOSFET manufactured by STMicroelectronics, rated for 250V drain-to-source voltage and 8A continuous drain current in a Through Hole TO-220 package. This device is classified as obsolete, making equivalent and substitute parts necessary for ongoing design support and procurement.

The IRF634 operates at a maximum junction temperature of 150°C and dissipates up to 80W under specified conditions. It features a gate threshold voltage of 4V at 250µA and an on-state resistance of 450mOhm at 4A and 10V gate-source voltage. The part is RoHS3 compliant and carries unlimited moisture sensitivity level classification.

Substiute Parts

IRF634

STMicroelectronicsIn Stock: 1382IRF634 Datasheet

Current PartRFQ

RCX080N25

Rohm SemiconductorIn Stock: 7926RCX080N25 Datasheet

DirectRFQ

IRF624PBF

Vishay SiliconixIn Stock: 1260IRF624PBF Datasheet

SimilarRFQ

IRF634PBF

Vishay SiliconixIn Stock: 38338IRF634PBF Datasheet

SimilarRFQ

Key Parameters

Substitute Part Grouping Explanation

Substitution of the IRF634 is determined by electrical and mechanical compatibility across the following critical parameters:

Voltage Rating: All substitute parts must maintain a Vdss rating of 250V to ensure safe operation within the original circuit design envelope.

Current Rating: The continuous drain current (Id) must be equal to or greater than 8A at 25°C to support the original load requirements.

Gate Drive Voltage: All parts operate at 10V drive voltage, ensuring compatibility with existing gate drive circuits.

Gate Threshold Voltage: Vgs(th) must be within acceptable limits (4V to 5V) to maintain consistent switching behavior.

Package and Mounting: All substitute parts use Through Hole TO-220 package variants (TO-220AB or TO-220FM), ensuring mechanical and thermal compatibility with existing PCB layouts.

Compliance: All substitute parts are RoHS3 compliant and carry unlimited moisture sensitivity level classification, matching the original part's environmental and regulatory status.

The IRF634 is listed as obsolete; therefore, active-status alternatives are required for new procurement and design continuity.

Parameter Comparison

Engineering Selection Recommendations

RCX080N25 (Rohm Semiconductor) – Direct Substitute

The RCX080N25 is classified as a direct substitute based on matching voltage rating (250V), current rating (8A), and drive voltage (10V). Both parts maintain identical gate threshold voltage specifications and operate at the same maximum junction temperature (150°C). The RCX080N25 is currently in active production status with 7890 units in stock, providing reliable long-term availability.

The RCX080N25 carries RoHS3 compliance and unlimited moisture sensitivity level classification, matching the original part's regulatory and environmental certifications. The on-state resistance specification (600mOhm @ 4A, 10V) is slightly higher than the IRF634 (450mOhm), resulting in marginally increased power dissipation. The gate charge is significantly lower (15nC versus 51.8nC), enabling faster switching response. The maximum gate-source voltage rating is higher (±30V versus ±20V), providing additional gate drive margin.

IRF634PBF (Vishay Siliconix) – Similar Substitute

The IRF634PBF is classified as a similar substitute with near-identical electrical characteristics to the original IRF634. It maintains the same voltage rating (250V), current rating (8.1A), and on-state resistance specification (450mOhm @ 5.1A, 10V). The gate threshold voltage and maximum gate-source voltage match the original part exactly (4V and ±20V respectively).

The IRF634PBF is currently in active production with 38261 units in stock, ensuring robust procurement availability. It carries identical RoHS3 compliance and unlimited moisture sensitivity level classification. The power dissipation rating (74W) is slightly lower than the original (80W), and the gate charge (41nC) is lower than the original (51.8nC). The operating temperature range extends to -55°C, providing enhanced low-temperature performance compared to the original specification.

IRF624PBF (Vishay Siliconix) – Limited Compatibility

The IRF624PBF is classified as a similar substitute with significant current rating limitations. The continuous drain current is rated at 4.4A, which is substantially below the original IRF634 specification of 8A. This part is suitable only for applications where the actual circuit current requirement does not exceed 4.4A.

The IRF624PBF maintains the same voltage rating (250V) and drive voltage (10V) as the original part. It features a lower on-state resistance (1.1Ohm @ 2.6A, 10V) and significantly lower gate charge (14nC), enabling faster switching. The part is currently in active production with 1199 units in stock and carries identical RoHS3 compliance and unlimited moisture sensitivity level classification. The operating temperature range extends to -55°C.

Frequently Asked Questions (FAQ)

Q: Can the RCX080N25 directly replace the IRF634 in all applications?

A: The RCX080N25 is electrically compatible with the IRF634 across all critical parameters: voltage rating (250V), current rating (8A), and drive voltage (10V). Both parts use Through Hole TO-220 packaging and are RoHS3 compliant. The RCX080N25 features lower gate charge (15nC versus 51.8nC), which may improve switching speed in gate-drive-limited circuits. The slightly higher on-state resistance (600mOhm versus 450mOhm) results in marginally increased power dissipation. Thermal design verification is recommended for applications operating near the 80W power dissipation limit.

Q: What is the difference between the IRF634PBF and the original IRF634?

A: The IRF634PBF is manufactured by Vishay Siliconix and maintains nearly identical electrical specifications to the original STMicroelectronics IRF634. Both parts are rated for 250V, 8A continuous drain current, and 450mOhm on-state resistance at 10V gate drive. The IRF634PBF is currently in active production status, whereas the original IRF634 is obsolete. The IRF634PBF offers an extended operating temperature range (-55°C to 150°C) and slightly lower power dissipation (74W versus 80W). Both parts use TO-220-3 packaging and are RoHS3 compliant.

Q: Why is the IRF624PBF listed as a similar substitute if it has lower current rating?

A: The IRF624PBF is listed as a similar substitute because it shares the same voltage rating (250V), package type (TO-220-3), and drive voltage (10V) as the IRF634. However, its continuous drain current rating of 4.4A is substantially lower than the IRF634's 8A specification. The IRF624PBF is suitable only for applications where the actual circuit current does not exceed 4.4A. For applications requiring the full 8A current capability, the RCX080N25 or IRF634PBF are appropriate selections.

Q: Are all substitute parts available in the same packaging?

A: All substitute parts use Through Hole TO-220 package variants. The IRF634, IRF624PBF, and IRF634PBF use the standard TO-220-3 package. The RCX080N25 uses the TO-220-3 Full Pack variant (TO-220FM), which is mechanally and thermally compatible with standard TO-220-3 PCB layouts. No PCB redesign is required for package compatibility.

Q: What is the significance of the gate charge difference between these parts?

A: Gate charge (Qg) determines the amount of charge required to switch the MOSFET from off to on state. The IRF634 requires 51.8nC at 10V gate drive, while the RCX080N25 requires only 15nC and the IRF634PBF requires 41nC. Lower gate charge enables faster switching transitions and reduces gate drive power consumption. In gate-drive-limited circuits, the RCX080N25 or IRF624PBF may provide improved switching performance. In current-limited gate drive circuits, the higher gate charge of the IRF634PBF may require gate drive circuit verification.

Q: Are all substitute parts RoHS3 compliant?

A: Yes. The IRF634, RCX080N25, IRF624PBF, and IRF634PBF are all RoHS3 compliant. All parts carry unlimited moisture sensitivity level (MSL 1) classification, indicating no special moisture control requirements during storage or handling.

Q: What is the impact of the on-state resistance difference on circuit performance?

A: The IRF634 and IRF634PBF both specify 450mOhm on-state resistance at 10V gate drive. The RCX080N25 specifies 600mOhm, representing a 33% increase in on-state resistance. At 8A continuous drain current, this results in approximately 0.48W additional power dissipation in the RCX080N25 compared to the IRF634. For applications operating near thermal limits, thermal design verification is required. The IRF624PBF specifies 1.1Ohm on-state resistance but at a lower current level (2.6A), making direct comparison inappropriate for 8A applications.