IRF740FI MOSFET — Specifications & Equivalents
Manufacturer: Commonly produced by International Rectifier (now Infineon)
About the IRF740FI
The IRF740FI is an N-channel MOSFET with a drain–source voltage (VDS) rating of 400 V, a continuous drain current (ID) of 5.5 A and an on-resistance (RDS(on)) of 0.55 Ω. It can dissipate up to 40 W and is rated to a junction temperature of 150 °C. It is supplied in the ISOWATT220 package.
At a glance
- Type: N-channel MOSFET
- Max drain–source voltage (VDS): 400 V
- Max continuous drain current (ID): 5.5 A
- On-resistance (RDS(on)): 0.55 Ω
- Gate threshold (VGS(th)): 4 V
- Power dissipation (PD): 40 W
- Max junction temperature (TJ): 150 °C
- Package: ISOWATT220
- Manufacturer: Commonly produced by International Rectifier (now Infineon)
Typical applications
With its 400 V drain–source rating the IRF740FI 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
With a gate threshold (VGS(th)) of 4 V this is not a logic-level device: driving the gate directly from a 3.3 V or 5 V microcontroller pin will leave it only partly on and cause it to overheat. Use a gate driver or level shifter, typically taking VGS to 10 V.
Keep gate–source voltage within the ±20 V maximum; exceeding it punctures the gate oxide and destroys the device permanently.
Total gate charge (Qg) of 63 nC sets the drive current required: average gate current is roughly Qg × switching frequency, so faster switching needs a stronger driver.
Switching behaviour is characterised by a rise time of 15 ns and an output capacitance (Coss) of 450 pF, which together with the gate drive determines switching loss and the practical upper frequency limit.
Choosing a replacement for the IRF740FI
A drop-in substitute for the IRF740FI must be the same N-channel type and offer a drain–source rating of at least 400 V, a continuous drain current rating of at least 5.5 A, an on-resistance no higher than 0.55 Ω if efficiency and heat matter and a comparable gate threshold, so your existing gate drive still fully enhances the device.
Mechanically, check the replacement against the ISOWATT220 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 IRF740FI?
The IRF740FI is an N-channel MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 400 V drain-source and 5.5 A continuous drain current.
What is the maximum voltage of the IRF740FI?
The IRF740FI 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 IRF740FI handle?
It is rated for 5.5 A of continuous drain current, with power dissipation limited to 40 W. Real-world capability depends on your heatsinking and ambient temperature.
What is the on-resistance of the IRF740FI?
On-resistance (Rds(on)) is 0.55 Ω. Multiply by the square of your load current to estimate conduction loss.
Is the IRF740FI logic-level compatible?
No. The gate threshold is 4 V, so a 3.3 V or 5 V logic output cannot fully turn it on. Use a gate driver and take Vgs to around 10 V.
What package does the IRF740FI come in?
It is listed in ISOWATT220. Verify the pinout of the specific variant, as one outline can carry different pin assignments.
What can I use to replace the IRF740FI?
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) | 400 V |
| Gate-Source Voltage (Vgs) | 20 V |
| Gate Threshold Voltage (Vgsth) | 4 V |
| Drain Current (Id) | 5.5 A |
| Drain-Source On-Resistance (Rds) | 0.55 |
| Total Gate Charge (Qg) | 63 |
| Rise Time (tr) | 15 |
| Output Capacitance (Coss) | 450 |
| Junction Temperature (Tj) | 150 °C |
| Package | ISOWATT220 |
| Power Dissipation (Pd) | 40 W |
Equivalent & Replacement Parts
No verified equivalents are listed for IRF740FI yet.