2N391 bipolar transistor — Specifications & Equivalents

About the 2N391

The 2N391 is a PNP bipolar transistor with a collector–emitter voltage (V_CEO) rating of 40 V, a continuous collector current (I_C) of 5 A and a DC current gain (h_FE) of minimum 30. It can dissipate up to 45 W and is rated to a junction temperature of 85 °C. It is supplied in the TO3 package.

At a glance

• Type: PNP bipolar transistor
• Max collector–emitter voltage (V_CEO): 40 V
• Max collector current (I_C): 5 A
• DC current gain (h_FE): minimum 30
• Power dissipation (P_D): 45 W
• Max junction temperature (T_J): 85 °C
• Package: TO3
• Manufacturer: Multi-source (JEDEC registered part number)

Typical applications

Judging from its ratings the 2N391 is generally applied in power output and driver stages.

The quoted current gain of minimum 30 determines the base drive needed: divide your target collector current by the minimum h_FE, not the typical figure, when sizing the base resistor.

Biasing and absolute maximum ratings

Absolute-maximum breakdown limits are V_CEO 40 V, V_CBO 50 V and V_EBO 20 V (magnitudes). The emitter–base rating is the easiest to overlook and is often only a few volts, so protect the junction against reverse drive.

Dissipation is capped at 45 W, and that figure assumes the datasheet's mounting and ambient conditions — derate it for your own thermal design.

Choosing a replacement for the 2N391

A drop-in substitute for the 2N391 must be the same PNP type and offer a collector–emitter rating of at least 40 V, a collector current rating of at least 5 A and current gain in the same ballpark as minimum 30.

Mechanically, check the replacement against the TO3 footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.

Because 2N391 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 2N391?

The 2N391 is a PNP bipolar junction transistor (BJT). It is rated for 40 V collector-emitter and 5 A continuous collector current.

What is the maximum voltage of the 2N391?

Maximum collector-emitter voltage (Vceo) is 40 V, and collector-base (Vcbo) is 50 V.

How much current can the 2N391 handle?

Continuous collector current is rated at 5 A, with dissipation limited to 45 W.

What is the hFE of the 2N391?

DC current gain (hFE) is quoted as minimum 30. Size base drive from the minimum value so the transistor saturates fully across production spread.

What package does the 2N391 come in?

It is listed in TO3. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the 2N391?

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.