BD140 bipolar transistor — Specifications & Equivalents

About the BD140

The BD140 is a PNP bipolar transistor with a collector–emitter voltage (V_CEO) rating of 80 V, a continuous collector current (I_C) of 1 A and a DC current gain (h_FE) of minimum 40. It can dissipate up to 12 W and is rated to a junction temperature of 150 °C. It is supplied in the TO126 package.

At a glance

• Type: PNP bipolar transistor
• Max collector–emitter voltage (V_CEO): 80 V
• Max collector current (I_C): 1 A
• DC current gain (h_FE): minimum 40
• Transition frequency (f_T): 50 MHz
• Power dissipation (P_D): 12 W
• Max junction temperature (T_J): 150 °C
• Package: TO126
• Manufacturer: Multi-source (Pro Electron registered part number)

Typical applications

Judging from its ratings the BD140 is generally applied in power output and driver stages.

A transition frequency (f_T) of 50 MHz indicates the frequency range over which useful current gain remains available.

The quoted current gain of minimum 40 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 80 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 12 W, and that figure assumes the datasheet's mounting and ambient conditions — derate it for your own thermal design.

Choosing a replacement for the BD140

A drop-in substitute for the BD140 must be the same PNP type and offer a collector–emitter rating of at least 80 V, a collector current rating of at least 1 A, current gain in the same ballpark as minimum 40 and a transition frequency of at least 50 MHz for the same bandwidth.

Mechanically, check the replacement against the TO126 footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.

Because BD140 is a Pro Electron-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 BD140?

The BD140 is a PNP bipolar junction transistor (BJT). It is rated for 80 V collector-emitter and 1 A continuous collector current.

What is the maximum voltage of the BD140?

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

How much current can the BD140 handle?

Continuous collector current is rated at 1 A, with dissipation limited to 12 W.

What is the hFE of the BD140?

DC current gain (hFE) is quoted as minimum 40. Size base drive from the minimum value so the transistor saturates fully across production spread.

What package does the BD140 come in?

It is listed in TO126. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the BD140?

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.