2SD721 bipolar transistor — Specifications & Equivalents

About the 2SD721

The 2SD721 is an NPN bipolar transistor with a collector–emitter voltage (V_CEO) rating of 80 V, a continuous collector current (I_C) of 10 A and a DC current gain (h_FE) of minimum 500. It can dissipate up to 80 W and is rated to a junction temperature of 135 °C. It is supplied in the TO220 package.

At a glance

• Type: NPN bipolar transistor
• Max collector–emitter voltage (V_CEO): 80 V
• Max collector current (I_C): 10 A
• DC current gain (h_FE): minimum 500
• Power dissipation (P_D): 80 W
• Max junction temperature (T_J): 135 °C
• Package: TO220
• Manufacturer: Multi-source (JIS registered part number)

Typical applications

Judging from its ratings the 2SD721 is generally applied in power output and driver stages.

The quoted current gain of minimum 500 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 80 V, V_CBO 100 V and V_EBO 1 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 80 W, and that figure assumes the datasheet's mounting and ambient conditions — derate it for your own thermal design.

Choosing a replacement for the 2SD721

A drop-in substitute for the 2SD721 must be the same NPN type and offer a collector–emitter rating of at least 80 V, a collector current rating of at least 10 A and current gain in the same ballpark as minimum 500.

Mechanically, check the replacement against the TO220 footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.

Because 2SD721 is a JIS-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 2SD721?

The 2SD721 is an NPN bipolar junction transistor (BJT). It is rated for 80 V collector-emitter and 10 A continuous collector current.

What is the maximum voltage of the 2SD721?

Maximum collector-emitter voltage (Vceo) is 80 V, and collector-base (Vcbo) is 100 V.

How much current can the 2SD721 handle?

Continuous collector current is rated at 10 A, with dissipation limited to 80 W.

What is the hFE of the 2SD721?

DC current gain (hFE) is quoted as minimum 500. Size base drive from the minimum value so the transistor saturates fully across production spread.

What package does the 2SD721 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 2SD721?

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.