IRFB4321 MOSFET — Specifications & Equivalents
Manufacturer: Commonly produced by International Rectifier (now Infineon)
About the IRFB4321
The IRFB4321 is an N-channel MOSFET with a drain–source voltage (VDS) rating of 150 V, a continuous drain current (ID) of 85 A and an on-resistance (RDS(on)) of 0.015 Ω. It can dissipate up to 350 W and is rated to a junction temperature of 175 °C. It is supplied in the TO220AB package.
At a glance
- Type: N-channel MOSFET
- Max drain–source voltage (VDS): 150 V
- Max continuous drain current (ID): 85 A
- On-resistance (RDS(on)): 0.015 Ω
- Power dissipation (PD): 350 W
- Max junction temperature (TJ): 175 °C
- Package: TO220AB
- Manufacturer: Commonly produced by International Rectifier (now Infineon)
Typical applications
With its 150 V drain–source rating the IRFB4321 sits in the medium-voltage class of switching MOSFETs, typically found in 48 V and 96 V distribution systems, solar and telecom power stages, DC motor drives and intermediate-bus DC-DC converters.
The 85 A current rating puts it in high-current territory, where conduction loss (I² × RDS(on)) and thermal design usually matter more than switching loss. Budget for adequate copper area and a heatsink.
The low 0.015 Ω on-resistance keeps conduction loss down, which suits synchronous rectification and continuous high-current paths.
Gate drive and switching notes
Keep gate–source voltage within the ±30 V maximum; exceeding it punctures the gate oxide and destroys the device permanently.
Switching behaviour is characterised by a rise time of 60 ns and an output capacitance (Coss) of 390 pF, which together with the gate drive determines switching loss and the practical upper frequency limit.
Choosing a replacement for the IRFB4321
A drop-in substitute for the IRFB4321 must be the same N-channel type and offer a drain–source rating of at least 150 V, a continuous drain current rating of at least 85 A and an on-resistance no higher than 0.015 Ω if efficiency and heat matter.
Mechanically, check the replacement against the TO220AB footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.
Where the application switches inductive loads or runs near the voltage limit, keep extra headroom rather than choosing a part that only just meets the original numbers.
Frequently asked questions
What is the IRFB4321?
The IRFB4321 is an N-channel MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 150 V drain-source and 85 A continuous drain current.
What is the maximum voltage of the IRFB4321?
The IRFB4321 has a maximum drain-source voltage (Vds) of 150 V. Treat this as an absolute maximum and design with margin, especially when switching inductive loads.
How much current can the IRFB4321 handle?
It is rated for 85 A of continuous drain current, with power dissipation limited to 350 W. Real-world capability depends on your heatsinking and ambient temperature.
What is the on-resistance of the IRFB4321?
On-resistance (Rds(on)) is 0.015 Ω. Multiply by the square of your load current to estimate conduction loss.
What package does the IRFB4321 come in?
It is listed in TO220AB. Verify the pinout of the specific variant, as one outline can carry different pin assignments.
What can I use to replace the IRFB4321?
No verified equivalents are listed yet. Choose a part of the same polarity that meets or exceeds every rating above and shares a compatible package and pinout.
Key Specifications
| Type | MOSFET |
|---|---|
| Channel Type | N -Channel |
| Drain-Source Voltage (Vds) | 150 V |
| Gate-Source Voltage (Vgs) | 30 V |
| Drain Current (Id) | 85 A |
| Drain-Source On-Resistance (Rds) | 0.015 |
| Rise Time (tr) | 60 nS |
| Output Capacitance (Coss) | 390 pF |
| Junction Temperature (Tj) | 175 °C |
| Package | TO220AB |
| Power Dissipation (Pd) | 350 W |
Equivalent & Replacement Parts
No verified equivalents are listed for IRFB4321 yet.