18N65 MOSFET — Specifications & Equivalents
About the 18N65
The 18N65 is an N-channel MOSFET with a drain–source voltage (VDS) rating of 650 V, a continuous drain current (ID) of 18 A and an on-resistance (RDS(on)) of 0.36 Ω. It can dissipate up to 390 W and is rated to a junction temperature of 150 °C. It is available in TO-3P, TO-247 and TO-230 packages, so confirm the pinout of the exact variant you order.
At a glance
- Type: N-channel MOSFET
- Max drain–source voltage (VDS): 650 V
- Max continuous drain current (ID): 18 A
- On-resistance (RDS(on)): 0.36 Ω
- Power dissipation (PD): 390 W
- Max junction temperature (TJ): 150 °C
- Package: TO-3P, TO-247, TO-230
Typical applications
With its 650 V drain–source rating the 18N65 sits in the high-voltage (offline) class of switching MOSFETs, typically found in primary-side switching in offline SMPS (flyback, forward and quasi-resonant), active PFC boost stages, half-bridge and full-bridge inverters, induction heating and electronic ballasts and BLDC and AC motor drives. The rating leaves usable margin above the ~325 V DC bus obtained by rectifying 230 VAC mains, which is why this class dominates offline power supplies.
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 280 pF, which together with the gate drive determines switching loss and the practical upper frequency limit.
Choosing a replacement for the 18N65
A drop-in substitute for the 18N65 must be the same N-channel type and offer a drain–source rating of at least 650 V, a continuous drain current rating of at least 18 A and an on-resistance no higher than 0.36 Ω if efficiency and heat matter.
Mechanically, check the replacement against the TO-3P, TO-247 and TO-230 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 18N65?
The 18N65 is an N-channel MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 650 V drain-source and 18 A continuous drain current.
What is the maximum voltage of the 18N65?
The 18N65 has a maximum drain-source voltage (Vds) of 650 V. Treat this as an absolute maximum and design with margin, especially when switching inductive loads.
How much current can the 18N65 handle?
It is rated for 18 A of continuous drain current, with power dissipation limited to 390 W. Real-world capability depends on your heatsinking and ambient temperature.
What is the on-resistance of the 18N65?
On-resistance (Rds(on)) is 0.36 Ω. Multiply by the square of your load current to estimate conduction loss.
What package does the 18N65 come in?
It is listed in TO-3P, TO-247 and TO-230. Verify the pinout of the specific variant, as one outline can carry different pin assignments.
What can I use to replace the 18N65?
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) | 650 V |
| Gate-Source Voltage (Vgs) | 30 V |
| Drain Current (Id) | 18 A |
| Drain-Source On-Resistance (Rds) | 0.36 |
| Rise Time (tr) | 60 nS |
| Output Capacitance (Coss) | 280 pF |
| Junction Temperature (Tj) | 150 °C |
| Package | TO-3P TO-247 TO-230 |
| Power Dissipation (Pd) | 390 W |
Equivalent & Replacement Parts
No verified equivalents are listed for 18N65 yet.