FDA8440 MOSFET — Specifications & Equivalents

About the FDA8440

The FDA8440 is an N-channel MOSFET with a drain–source voltage (V_DS) rating of 40 V, a continuous drain current (I_D) of 100 A and an on-resistance (R_DS(on)) of 0.0022 Ω. It can dissipate up to 306 W and is rated to a junction temperature of 175 °C. It is supplied in the TO3PN package.

At a glance

• Type: N-channel MOSFET
• Max drain–source voltage (V_DS): 40 V
• Max continuous drain current (I_D): 100 A
• On-resistance (R_DS(on)): 0.0022 Ω
• Power dissipation (P_D): 306 W
• Max junction temperature (T_J): 175 °C
• Package: TO3PN

Typical applications

With its 40 V drain–source rating the FDA8440 sits in the low-voltage class of switching MOSFETs, typically found in 12 V and 24 V automotive and industrial rails, synchronous buck converters, load switching and reverse-polarity protection and H-bridges for small motors.

The 100 A current rating puts it in high-current territory, where conduction loss (I² × R_DS(on)) and thermal design usually matter more than switching loss. Budget for adequate copper area and a heatsink.

The low 0.0022 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 ±20 V maximum; exceeding it punctures the gate oxide and destroys the device permanently.

Choosing a replacement for the FDA8440

A drop-in substitute for the FDA8440 must be the same N-channel type and offer a drain–source rating of at least 40 V, a continuous drain current rating of at least 100 A and an on-resistance no higher than 0.0022 Ω if efficiency and heat matter.

Mechanically, check the replacement against the TO3PN 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 FDA8440?

The FDA8440 is an N-channel MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 40 V drain-source and 100 A continuous drain current.

What is the maximum voltage of the FDA8440?

The FDA8440 has a maximum drain-source voltage (Vds) of 40 V. Treat this as an absolute maximum and design with margin, especially when switching inductive loads.

How much current can the FDA8440 handle?

It is rated for 100 A of continuous drain current, with power dissipation limited to 306 W. Real-world capability depends on your heatsinking and ambient temperature.

What is the on-resistance of the FDA8440?

On-resistance (Rds(on)) is 0.0022 Ω. Multiply by the square of your load current to estimate conduction loss.

What package does the FDA8440 come in?

It is listed in TO3PN. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the FDA8440?

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.