18N25 MOSFET — Specifications & Equivalents

About the 18N25

The 18N25 is a MOSFET with a drain–source voltage (V_DS) rating of 250 V and a continuous drain current (I_D) of 18 A. It can dissipate up to 138 W and is rated to a junction temperature of 150 °C. It is available in TO-263 and TO-220F packages, so confirm the pinout of the exact variant you order.

At a glance

• Type: MOSFET
• Max drain–source voltage (V_DS): 250 V
• Max continuous drain current (I_D): 18 A
• Power dissipation (P_D): 138 W
• Max junction temperature (T_J): 150 °C
• Package: TO-263, TO-220F

Typical applications

With its 250 V drain–source rating the 18N25 sits in the medium-high-voltage class of switching MOSFETs, typically found in telecom and industrial DC rails, boost and flyback converters, LED and backlight drivers and power-factor-correction stages. Common where the bus sits well above 100 V but below rectified mains.

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.

Switching behaviour is characterised by an output capacitance (C_oss) of 330 pF, which together with the gate drive determines switching loss and the practical upper frequency limit.

Choosing a replacement for the 18N25

A drop-in substitute for the 18N25 should match its polarity and offer a drain–source rating of at least 250 V and a continuous drain current rating of at least 18 A.

Mechanically, check the replacement against the TO-263 and TO-220F 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 18N25?

The 18N25 is a MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 250 V drain-source and 18 A continuous drain current.

What is the maximum voltage of the 18N25?

The 18N25 has a maximum drain-source voltage (Vds) of 250 V. Treat this as an absolute maximum and design with margin, especially when switching inductive loads.

How much current can the 18N25 handle?

It is rated for 18 A of continuous drain current, with power dissipation limited to 138 W. Real-world capability depends on your heatsinking and ambient temperature.

What package does the 18N25 come in?

It is listed in TO-263 and TO-220F. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the 18N25?

This page lists 17 candidate equivalents matched on electrical ratings and package. Any replacement should meet or exceed the original voltage, current and dissipation figures and use a compatible drive level.