IRF840S MOSFET — Specifications & Equivalents
Manufacturer: Commonly produced by International Rectifier (now Infineon)
About the IRF840S
The IRF840S is a MOSFET with a drain–source voltage (VDS) rating of 500 V and a continuous drain current (ID) of 8 A. It can dissipate up to 125 W and is rated to a junction temperature of 150 °C. It is supplied in the TO263 package.
At a glance
- Type: MOSFET
- Max drain–source voltage (VDS): 500 V
- Max continuous drain current (ID): 8 A
- Power dissipation (PD): 125 W
- Max junction temperature (TJ): 150 °C
- Package: TO263
- Manufacturer: Commonly produced by International Rectifier (now Infineon)
Typical applications
With its 500 V drain–source rating the IRF840S 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 ±20 V maximum; exceeding it punctures the gate oxide and destroys the device permanently.
Switching behaviour is characterised by an output capacitance (Coss) of 310 pF, which together with the gate drive determines switching loss and the practical upper frequency limit.
Choosing a replacement for the IRF840S
A drop-in substitute for the IRF840S should match its polarity and offer a drain–source rating of at least 500 V and a continuous drain current rating of at least 8 A.
Mechanically, check the replacement against the TO263 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 IRF840S?
The IRF840S is a MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 500 V drain-source and 8 A continuous drain current.
What is the maximum voltage of the IRF840S?
The IRF840S 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 IRF840S handle?
It is rated for 8 A of continuous drain current, with power dissipation limited to 125 W. Real-world capability depends on your heatsinking and ambient temperature.
What package does the IRF840S come in?
It is listed in TO263. Verify the pinout of the specific variant, as one outline can carry different pin assignments.
What can I use to replace the IRF840S?
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 | 125 W |
|---|---|
| |Vds|ⓘ - Maximum Drain-Source Voltage | 500 V |
| |Vgs|ⓘ - Maximum Gate-Source Voltage | 20 V |
| |Vgs(th)|ⓘ - Maximum Gate-Threshold Voltage | 4 V |
| |Id| ⓘ - Maximum Drain Current | 8 A |
| Tj ⓘ - Maximum Junction Temperature | 150 °C |
| Cossⓘ - Output Capacitance | 310 pF |
| Package | TO263 |
| Advanced Power MOSFETFEATURESBVDSS = 500 V Avalanche Rugged TechnologyRDS(on) = 0.85 Rugged Gate Oxide Technology Lower Input CapacitanceID = 8 A Improved Gate Charge Extended Safe Operating Area Lower Leakage Current | 10 A (Max.) @ VDS = 500V Lower RDS(ON) : 0.638 (Typ.)1231.Gate 2. Drain 3. SourceAbsolute Maximum RatingsSymbol Characteristic Val |
| INCHANGE Semiconductor isc Product Specification isc N-Channel Mosfet Transistor IRF840 FEATURES Drain Current ID=8.0A@ TC=25 Drain Source Voltage- | VDSS= 500V(Min) Static Drain-Source On-Resistance : RDS(on) = 0.85(Max) DESCRITION Designed for high voltage, high speed switching power applic- ations such as switching regulators, converters, solenoid an |
| isc N-Channel Mosfet Transistor IRF840AFEATURESDrain Source Voltage- | V = 500V(Min)DSSStatic Drain-Source On-Resistance: R = 0.85(Max)DS(on)Fast Switching SpeedMinimum Lot-to-Lot variations for robust deviceperformance and reliable operationDESCRITIONSwitch mode power supplyUninterruptable power supplyHigh speed power switchingABSOLUTE MAXIMUM |