IRFZ42 MOSFET — Specifications & Equivalents
Manufacturer: Commonly produced by International Rectifier (now Infineon)
About the IRFZ42
The IRFZ42 is an N-channel MOSFET with a drain–source voltage (VDS) rating of 50 V, a continuous drain current (ID) of 35 A and an on-resistance (RDS(on)) of 0.035 Ω. It can dissipate up to 125 W and is rated to a junction temperature of 150 °C. It is supplied in the TO220 package.
At a glance
- Type: N-channel MOSFET
- Max drain–source voltage (VDS): 50 V
- Max continuous drain current (ID): 35 A
- On-resistance (RDS(on)): 0.035 Ω
- Power dissipation (PD): 125 W
- Max junction temperature (TJ): 150 °C
- Package: TO220
- Manufacturer: Commonly produced by International Rectifier (now Infineon)
Typical applications
With its 50 V drain–source rating the IRFZ42 sits in the low-voltage class of switching MOSFETs, typically found in 12 V and 24 V automotive and industrial rails, synchronous buck converters, load switching and reverse-polarity protection and H-bridges for small motors.
The low 0.035 Ω on-resistance keeps conduction loss down, which suits synchronous rectification and continuous high-current paths.
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 a rise time of 60 ns and an output capacitance (Coss) of 1200 pF, which together with the gate drive determines switching loss and the practical upper frequency limit.
Choosing a replacement for the IRFZ42
A drop-in substitute for the IRFZ42 must be the same N-channel type and offer a drain–source rating of at least 50 V, a continuous drain current rating of at least 35 A and an on-resistance no higher than 0.035 Ω if efficiency and heat matter.
Mechanically, check the replacement against the TO220 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 IRFZ42?
The IRFZ42 is an N-channel MOSFET (metal-oxide-semiconductor field-effect transistor). It is rated for 50 V drain-source and 35 A continuous drain current.
What is the maximum voltage of the IRFZ42?
The IRFZ42 has a maximum drain-source voltage (Vds) of 50 V. Treat this as an absolute maximum and design with margin, especially when switching inductive loads.
How much current can the IRFZ42 handle?
It is rated for 35 A of continuous drain current, with power dissipation limited to 125 W. Real-world capability depends on your heatsinking and ambient temperature.
What is the on-resistance of the IRFZ42?
On-resistance (Rds(on)) is 0.035 Ω. Multiply by the square of your load current to estimate conduction loss.
What package does the IRFZ42 come in?
It is listed in TO220. Verify the pinout of the specific variant, as one outline can carry different pin assignments.
What can I use to replace the IRFZ42?
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) | 50 V |
| Gate-Source Voltage (Vgs) | 20 V |
| Drain Current (Id) | 35 A |
| Drain-Source On-Resistance (Rds) | 0.035 |
| Rise Time (tr) | 60 |
| Output Capacitance (Coss) | 1200 |
| Junction Temperature (Tj) | 150 °C |
| Package | TO220 |
| Power Dissipation (Pd) | 125 W |
Equivalent & Replacement Parts
No verified equivalents are listed for IRFZ42 yet.