STF12N50U MOSFET — Specifications & Equivalents
Manufacturer: Commonly produced by STMicroelectronics
About the STF12N50U
The STF12N50U is an N-channel MOSFET with a drain–source voltage (VDS) rating of 500 V, a continuous drain current (ID) of 10 A and an on-resistance (RDS(on)) of 0.8 Ω. It can dissipate up to 30 W and is rated to a junction temperature of 150 °C. It is supplied in the TO220FP package.
At a glance
- Type: N-channel MOSFET
- Max drain–source voltage (VDS): 500 V
- Max continuous drain current (ID): 10 A
- On-resistance (RDS(on)): 0.8 Ω
- Power dissipation (PD): 30 W
- Max junction temperature (TJ): 150 °C
- Package: TO220FP
- Manufacturer: Commonly produced by STMicroelectronics
Typical applications
With its 500 V drain–source rating the STF12N50U 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 17 ns and an output capacitance (Coss) of 159 pF, which together with the gate drive determines switching loss and the practical upper frequency limit.
Choosing a replacement for the STF12N50U
A drop-in substitute for the STF12N50U must be the same N-channel type and offer a drain–source rating of at least 500 V, a continuous drain current rating of at least 10 A and an on-resistance no higher than 0.8 Ω if efficiency and heat matter.
Mechanically, check the replacement against the TO220FP 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 STF12N50U?
The STF12N50U is an N-channel MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 500 V drain-source and 10 A continuous drain current.
What is the maximum voltage of the STF12N50U?
The STF12N50U has a maximum drain-source voltage (Vds) of 500 V. Treat this as an absolute maximum and design with margin, especially when switching inductive loads.
How much current can the STF12N50U handle?
It is rated for 10 A of continuous drain current, with power dissipation limited to 30 W. Real-world capability depends on your heatsinking and ambient temperature.
What is the on-resistance of the STF12N50U?
On-resistance (Rds(on)) is 0.8 Ω. Multiply by the square of your load current to estimate conduction loss.
What package does the STF12N50U come in?
It is listed in TO220FP. Verify the pinout of the specific variant, as one outline can carry different pin assignments.
What can I use to replace the STF12N50U?
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) | 500 V |
| Gate-Source Voltage (Vgs) | 30 V |
| Drain Current (Id) | 10 A |
| Drain-Source On-Resistance (Rds) | 0.8 |
| Rise Time (tr) | 17 nS |
| Output Capacitance (Coss) | 159 pF |
| Junction Temperature (Tj) | 150 °C |
| Package | TO220FP |
| Power Dissipation (Pd) | 30 W |
Equivalent & Replacement Parts
No verified equivalents are listed for STF12N50U yet.