3N70K MOSFET — Specifications & Equivalents

About the 3N70K

The 3N70K is an N-channel MOSFET with a drain–source voltage (V_DS) rating of 700 V, a continuous drain current (I_D) of 3 A and an on-resistance (R_DS(on)) of 2 Ω. It can dissipate up to 50 W and is rated to a junction temperature of 150 °C. It is available in TO-252 and TO-220F packages, so confirm the pinout of the exact variant you order.

At a glance

• Type: N-channel MOSFET
• Max drain–source voltage (V_DS): 700 V
• Max continuous drain current (I_D): 3 A
• On-resistance (R_DS(on)): 2 Ω
• Power dissipation (P_D): 50 W
• Max junction temperature (T_J): 150 °C
• Package: TO-252, TO-220F

Typical applications

With its 700 V drain–source rating the 3N70K 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.

On-resistance of 2 Ω is relatively high, so this part is better suited to low duty-cycle or low-current switching than to continuous high-current conduction.

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 20 ns and an output capacitance (C_oss) of 50 pF, which together with the gate drive determines switching loss and the practical upper frequency limit.

Choosing a replacement for the 3N70K

A drop-in substitute for the 3N70K must be the same N-channel type and offer a drain–source rating of at least 700 V, a continuous drain current rating of at least 3 A and an on-resistance no higher than 2 Ω if efficiency and heat matter.

Mechanically, check the replacement against the TO-252 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 3N70K?

The 3N70K is an N-channel MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 700 V drain-source and 3 A continuous drain current.

What is the maximum voltage of the 3N70K?

The 3N70K has a maximum drain-source voltage (Vds) of 700 V. Treat this as an absolute maximum and design with margin, especially when switching inductive loads.

How much current can the 3N70K handle?

It is rated for 3 A of continuous drain current, with power dissipation limited to 50 W. Real-world capability depends on your heatsinking and ambient temperature.

What is the on-resistance of the 3N70K?

On-resistance (Rds(on)) is 2 Ω. Multiply by the square of your load current to estimate conduction loss.

What package does the 3N70K come in?

It is listed in TO-252 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 3N70K?

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.