onsemi BD243CTU

Overview

BD243CTU from ON Semiconductor (formerly Fairchild) is an NPN epitaxial silicon power transistor in TO-220 package, rated for 100 V V_CEO, 6 A DC collector current, and 65 W power dissipation at T_C = 25°C; used in medium-power linear regulators and switching applications such as DC motor drivers and power supply output stages.

For engineers reviewing the BD243CTU datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO = 100 V, I_C = 6 A, h_FE ≥ 15 at I_C = 3 A, V_CE(sat) ≤ 1.5 V at I_C = 6 A / I_B = 1 A, and TO-220 thermal performance under forced-air or heatsink conditions.

Technical Context

The BD243CTU operates as a medium-power NPN bipolar junction transistor optimized for linear amplification and hard-switching duty. Its 100 V V_CEO rating enables use in 48 V industrial bus and 24 V automotive auxiliary circuits, while its 65 W P_C at T_C = 25°C supports continuous conduction with appropriate heatsinking.

It exhibits h_FE = 15 (min) at I_C = 3 A and V_CE = 4 V, and V_BE(on) = 2 V at I_C = 6 A - confirming base drive requirements for saturated switching. The device is not avalanche-rated and requires external protection against inductive kickback in relay or motor control.

Key Specifications

Pinout & Package

BD243CTU uses the standard TO-220 package with three leads: Pin 1 (Base), Pin 2 (Collector), Pin 3 (Emitter). The metal tab is electrically connected to the Collector and must be isolated from chassis unless circuit design intentionally references collector potential.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD243G, BD243CTU delivers higher thermal capacity via TO-220 metal tab and supports linear-mode operation; versus BD243C, it offers automated pick-and-place compatibility without electrical or performance trade-offs.

Availability

BD243CTU is available at Aetrix Electronics and suitable for DC motor control, linear voltage regulation, switched-mode power supply, and relay driver applications requiring stable component supply and long-term industrial availability.

Supply support for BD243CTU 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, intelligent power and sensing solutions for automotive, industrial, communications, and computing markets.

BD243CTU belongs to the BD243 family of medium-power NPN transistors designed for robust linear and switching applications in industrial power electronics, where reliability under sustained thermal stress and consistent gain across current range are critical.

FAQ

What is the maximum collector-emitter voltage rating for BD243CTU?

The BD243CTU has a maximum collector-emitter sustaining voltage V_CEO(sus) of 100 V at I_C = 30 mA and I_B = 0. This rating is confirmed in the Absolute Maximum Ratings table and Electrical Characteristics section of the official ON Semiconductor datasheet. It defines the upper limit for safe operation in switching or linear mode when the base is open.

Is BD243CTU pin-compatible with BD243C?

Yes, BD243CTU is pin-compatible with BD243C. Both share identical TO-220 package dimensions, terminal assignment (Base–Collector–Emitter), and electrical specifications. BD243CTU is the tape-and-reel packaging variant of the same die used in BD243C, intended for automated assembly without functional or thermal differences.

What is the typical DC current gain (h_FE) of BD243CTU at 3 A collector current?

The BD243CTU has a minimum h_FE of 15 at V_CE = 4 V and I_C = 3 A, per the Electrical Characteristics table. Typical values range higher depending on unit variation and temperature, but design must assume ≥15 to ensure sufficient base drive margin in saturation-critical applications.

Does BD243CTU require a heatsink in linear regulator applications?

Yes, BD243CTU requires a heatsink in linear regulator applications where power dissipation exceeds ~5 W. With a maximum P_C of 65 W at T_C = 25°C and thermal resistance θ_JC ≈ 1.9°C/W, even moderate dropout voltages (e.g., 5 V @ 3 A = 15 W) demand active or substantial passive cooling to maintain T_J < 150°C.

What is the collector-emitter saturation voltage (V_CE(sat)) for BD243CTU under full load?

The BD243CTU specifies V_CE(sat) ≤ 1.5 V at I_C = 6 A and I_B = 1 A. This value is measured under pulsed conditions (PW = 300 µs, duty cycle < 20%) and represents worst-case conduction loss in saturated switching - critical for calculating efficiency and thermal rise in motor or relay drivers.