2N4339 JFET — Specifications & Equivalents
Manufacturer: Multi-source (JEDEC registered part number)
About the 2N4339
The 2N4339 is an N-channel JFET with a drain–source voltage (VDS) rating of 50 V, a continuous drain current (ID) of 0.05 A and an on-resistance (RDS(on)) of 1700 Ω. It can dissipate up to 0.3 W and is rated to a junction temperature of 175 °C. It is supplied in the TO-18 package.
At a glance
- Type: N-channel JFET
- Max drain–source voltage (VDS): 50 V
- Max continuous drain current (ID): 0.05 A
- On-resistance (RDS(on)): 1700 Ω
- Power dissipation (PD): 0.3 W
- Max junction temperature (TJ): 175 °C
- Package: TO-18
- Manufacturer: Multi-source (JEDEC registered part number)
Typical applications
With its 50 V drain–source rating the 2N4339 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.
At 0.05 A it is aimed at small-signal and light-load switching rather than power conversion.
On-resistance of 1700 Ω is relatively high, so this part is better suited to low duty-cycle or low-current switching than to continuous high-current conduction.
Choosing a replacement for the 2N4339
A drop-in substitute for the 2N4339 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 0.05 A and an on-resistance no higher than 1700 Ω if efficiency and heat matter.
Mechanically, check the replacement against the TO-18 footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.
Because 2N4339 is a JEDEC-registered part number rather than one vendor's proprietary series, it is produced by several manufacturers. Datasheet figures vary slightly between them, so check the datasheet of the brand you actually buy — this also makes like-for-like sourcing easier.
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 2N4339?
The 2N4339 is an N-channel junction field-effect transistor (JFET). It is rated for 50 V drain-source and 0.05 A continuous drain current.
What is the maximum voltage of the 2N4339?
The 2N4339 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 2N4339 handle?
It is rated for 0.05 A of continuous drain current, with power dissipation limited to 0.3 W. Real-world capability depends on your heatsinking and ambient temperature.
What is the on-resistance of the 2N4339?
On-resistance (Rds(on)) is 1700 Ω. Multiply by the square of your load current to estimate conduction loss.
What package does the 2N4339 come in?
It is listed in TO-18. Verify the pinout of the specific variant, as one outline can carry different pin assignments.
What can I use to replace the 2N4339?
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 | JFET |
|---|---|
| Channel Type | N -Channel |
| Drain-Source Voltage (Vds) | 50 V |
| Gate-Source Voltage (Vgs) | 1.8 V |
| Drain Current (Id) | 0.05 A |
| Drain-Source On-Resistance (Rds) | 1700 |
| Junction Temperature (Tj) | 175 °C |
| Package | TO-18 |
| Power Dissipation (Pd) | 0.3 W |
Equivalent & Replacement Parts
No verified equivalents are listed for 2N4339 yet.