2N3771 bipolar transistor — Specifications & Equivalents

About the 2N3771

The 2N3771 is an NPN bipolar transistor with a collector–emitter voltage (V_CEO) rating of 40 V, a continuous collector current (I_C) of 30 A and a DC current gain (h_FE) of 15–60. It can dissipate up to 150 W and is rated to a junction temperature of -65 to +200°C. It is supplied in the TO-3 package.

At a glance

• Type: NPN bipolar transistor
• Max collector–emitter voltage (V_CEO): 40 V
• Max collector current (I_C): 30 A
• DC current gain (h_FE): 15–60
• Power dissipation (P_D): 150 W
• Max junction temperature (T_J): -65 to +200°C
• Package: TO-3
• Manufacturer: Multi-source (JEDEC registered part number)

Typical applications

Judging from its ratings the 2N3771 is generally applied in power output and driver stages.

The quoted current gain of 15–60 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 5 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 150 W, and that figure assumes the datasheet's mounting and ambient conditions — derate it for your own thermal design.

Choosing a replacement for the 2N3771

A drop-in substitute for the 2N3771 must be the same NPN type and offer a collector–emitter rating of at least 40 V, a collector current rating of at least 30 A and current gain in the same ballpark as 15–60.

Mechanically, check the replacement against the TO-3 footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.

Because 2N3771 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 2N3771?

The 2N3771 is an NPN bipolar junction transistor (BJT). It is rated for 40 V collector-emitter and 30 A continuous collector current.

What is the maximum voltage of the 2N3771?

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

How much current can the 2N3771 handle?

Continuous collector current is rated at 30 A, with dissipation limited to 150 W.

What is the hFE of the 2N3771?

DC current gain (hFE) is quoted as 15–60. Size base drive from the minimum value so the transistor saturates fully across production spread.

What package does the 2N3771 come in?

It is listed in TO-3. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the 2N3771?

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.