onsemi BD242CTU

Overview

BD242CTU from ON Semiconductor (formerly Fairchild) is a PNP epitaxial silicon power transistor in TO-220 package, rated for -100 V V_CEO, -3 A DC collector current, and 40 W power dissipation at T_C=25°C, used in medium-power linear regulation and switching applications such as DC motor control and power supply output stages.

For engineers reviewing the BD242CTU datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO rating, h_FE consistency at -3 A, V_CE(sat) under high-current switching, thermal derating behavior, and complementary pairing with BD241C devices.

Technical Context

The BD242CTU operates as a medium-power PNP bipolar junction transistor optimized for linear and switching operation in industrial and consumer power circuits. Its design supports stable DC current gain (h_FE ≥10 at I_C = -3 A) and low saturation voltage (-1.2 V at I_C = -3 A, I_B = -0.6 A), enabling efficient power stage implementation without forced cooling in many 24–48 V systems.

It features a rugged junction temperature rating of 150°C and storage range from -65°C to 150°C, with specified V_CEO(sus) matching its -100 V absolute maximum rating - confirming suitability for inductive load switching where voltage transients exceed steady-state supply rails.

Key Specifications

Pinout & Package

BD242CTU uses the standard TO-220 package with three leads: Pin 1 (Base), Pin 2 (Collector), Pin 3 (Emitter), mounted on a metal tab thermally and electrically connected to the Collector. The package provides mechanical robustness and direct heatsink mounting via the tab screw hole (ø3.60 mm).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP power transistor applications.

Compared with MJD242G and BD242C, the BD242CTU uniquely combines TO-220 through-hole compatibility, full 40 W thermal capability, and tape-and-reel delivery - making it optimal for hybrid production environments requiring both manual validation and automated assembly.

Availability

BD242CTU is available at Aetrix Electronics and suitable for DC motor control, linear voltage regulation, relay driving, and industrial power supply output stages requiring stable component supply across extended production lifecycles.

Supply support for BD242CTU includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

ON Semiconductor is a global semiconductor supplier delivering energy-efficient, high-performance silicon solutions for automotive, industrial, cloud computing, and IoT applications.

The BD242CTU belongs to ON Semiconductor's legacy power bipolar transistor family, designed specifically for cost-sensitive, medium-power linear and switching applications where ruggedness, thermal stability, and complementary NPN/PNP pairing are essential.

FAQ

What is the maximum continuous collector current rating for BD242CTU?

The BD242CTU has a maximum continuous collector current (I_C) rating of -3 A at T_C = 25°C. This rating decreases with rising case temperature per the published derating curve. At 100°C case temperature, the usable I_C drops to approximately -1.8 A. Designers must verify thermal interface resistance and heatsink performance to maintain safe junction temperature below 150°C during sustained operation of BD242CTU.

Is BD242CTU pin-compatible with BD242C?

Yes, BD242CTU is functionally and physically identical to BD242C - both share the same TO-220 package, pinout (Base–Collector–Emitter), and full electrical specifications. The "TU" suffix denotes tape-and-reel packaging for automated assembly, while BD242C is supplied in tube format. No circuit or layout changes are required when substituting BD242CTU for BD242C in existing designs.

What is the typical V_CE(sat) of BD242CTU under full-load conditions?

The BD242CTU exhibits a typical V_CE(sat) of -1.2 V when operated at I_C = -3 A and I_B = -0.6 A, as specified in the Fairchild datasheet. This value reflects the voltage drop across the collector-emitter junction in saturation, directly impacting conduction loss and thermal rise. Designers should use this figure - not the maximum - for efficiency calculations, while verifying worst-case margin using the -1.5 V max value under minimum h_FE conditions.

Can BD242CTU be used as a direct replacement for BD242B or BD242A?

No, BD242CTU is not a direct replacement for BD242B or BD242A due to differences in absolute maximum ratings: BD242CTU is rated for -100 V V_CEO, whereas BD242B is -80 V and BD242A is -60 V. Substituting BD242CTU in circuits designed for lower-voltage variants may introduce unnecessary cost and size overhead, but it is electrically safe. However, replacing BD242CTU with BD242B/A in a -100 V application risks catastrophic failure.

Does BD242CTU require a heatsink in all applications?

BD242CTU requires a heatsink whenever power dissipation exceeds ~2–3 W continuously, depending on ambient temperature and enclosure airflow. With its 40 W P_C rating at T_C = 25°C, even modest loads (e.g., -2 A at -5 V V_CE) generate 10 W - well above natural convection limits. The metal tab is electrically connected to the collector, so electrical isolation (e.g., mica washer + thermal paste) is mandatory when mounting to grounded heatsinks in BD242CTU applications.