18N40 MOSFET — Specifications & Equivalents
About the 18N40
The 18N40 is a MOSFET with a drain–source voltage (VDS) rating of 400 V and a continuous drain current (ID) of 18 A. It can dissipate up to 360 W and is rated to a junction temperature of 150 °C. It is available in TO-247, TO-220 and TO-220F1 packages, so confirm the pinout of the exact variant you order.
At a glance
- Type: MOSFET
- Max drain–source voltage (VDS): 400 V
- Max continuous drain current (ID): 18 A
- Power dissipation (PD): 360 W
- Max junction temperature (TJ): 150 °C
- Package: TO-247, TO-220, TO-220F1
Typical applications
With its 400 V drain–source rating the 18N40 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 ±30 V maximum; exceeding it punctures the gate oxide and destroys the device permanently.
Switching behaviour is characterised by an output capacitance (Coss) of 280 pF, which together with the gate drive determines switching loss and the practical upper frequency limit.
Choosing a replacement for the 18N40
A drop-in substitute for the 18N40 should match its polarity and offer a drain–source rating of at least 400 V and a continuous drain current rating of at least 18 A.
Mechanically, check the replacement against the TO-247, TO-220 and TO-220F1 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 18N40?
The 18N40 is a MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 400 V drain-source and 18 A continuous drain current.
What is the maximum voltage of the 18N40?
The 18N40 has a maximum drain-source voltage (Vds) of 400 V. Treat this as an absolute maximum and design with margin, especially when switching inductive loads.
How much current can the 18N40 handle?
It is rated for 18 A of continuous drain current, with power dissipation limited to 360 W. Real-world capability depends on your heatsinking and ambient temperature.
What package does the 18N40 come in?
It is listed in TO-247, TO-220 and TO-220F1. Verify the pinout of the specific variant, as one outline can carry different pin assignments.
What can I use to replace the 18N40?
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.
Key Specifications
| Pd ⓘ - Maximum Power Dissipation | 360 W |
|---|---|
| |Vds|ⓘ - Maximum Drain-Source Voltage | 400 V |
| |Vgs|ⓘ - Maximum Gate-Source Voltage | 30 V |
| |Id| ⓘ - Maximum Drain Current | 18 A |
| Tj ⓘ - Maximum Junction Temperature | 150 °C |
| Cossⓘ - Output Capacitance | 280 pF |
| Package | TO-247 TO-220 TO-220F1 |
| NGD18N40CLB,NGD18N40ACLBIgnition IGBT, 18 A, 400 VN-Channel DPAKThis Logic Level Insulated Gate Bipolar Transistor (IGBT) featuresmonolithic circuitry integrating ESD and Over-Voltage clampedhttp | //onsemi.comprotection for use in inductive coil drivers applications. Primary usesinclude Ignition, Direct Fuel Injection, or wherever high voltage and18 AMPS, 400 VOLTShigh curren |
| NGB18N40CLBT4Ignition IGBT18 Amps, 400 VoltsN-Channel D2PAKThis Logic Level Insulated Gate Bipolar Transistor (IGBT) featuresmonolithic circuitry integrating ESD and Over-Voltage clampedhttp | //onsemi.comprotection for use in inductive coil drivers applications. Primary usesinclude Ignition, Direct Fuel Injection, or wherever high voltage and 18 AMPS, 400 VOLTShigh current swit |