D209L bipolar transistor — Specifications & Equivalents

About the D209L

The D209L is an NPN bipolar transistor with a collector–emitter voltage (V_CEO) rating of 400 V, a continuous collector current (I_C) of 12 A and a DC current gain (h_FE) of minimum 8. It can dissipate up to 100 W and is rated to a junction temperature of 150 °C. It is supplied in the TO-3PN package.

At a glance

• Type: NPN bipolar transistor
• Max collector–emitter voltage (V_CEO): 400 V
• Max collector current (I_C): 12 A
• DC current gain (h_FE): minimum 8
• Transition frequency (f_T): 5 MHz
• Power dissipation (P_D): 100 W
• Max junction temperature (T_J): 150 °C
• Package: TO-3PN

Typical applications

Judging from its ratings the D209L is generally applied in power output and driver stages and high-voltage switching such as offline converters and lamp drivers.

A transition frequency (f_T) of 5 MHz indicates the frequency range over which useful current gain remains available.

The quoted current gain of minimum 8 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 400 V, V_CBO 700 V and V_EBO 9 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 100 W, and that figure assumes the datasheet's mounting and ambient conditions — derate it for your own thermal design.

Choosing a replacement for the D209L

A drop-in substitute for the D209L must be the same NPN type and offer a collector–emitter rating of at least 400 V, a collector current rating of at least 12 A, current gain in the same ballpark as minimum 8 and a transition frequency of at least 5 MHz for the same bandwidth.

Mechanically, check the replacement against the TO-3PN 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 D209L?

The D209L is an NPN bipolar junction transistor (BJT). It is rated for 400 V collector-emitter and 12 A continuous collector current.

What is the maximum voltage of the D209L?

Maximum collector-emitter voltage (Vceo) is 400 V, and collector-base (Vcbo) is 700 V.

How much current can the D209L handle?

Continuous collector current is rated at 12 A, with dissipation limited to 100 W.

What is the hFE of the D209L?

DC current gain (hFE) is quoted as minimum 8. Size base drive from the minimum value so the transistor saturates fully across production spread.

What package does the D209L come in?

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

What can I use to replace the D209L?

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.