onsemi BD243BTU

Overview

BD243BTU from Fairchild Semiconductor is an NPN epitaxial silicon power transistor in TO-220 package, rated for 80 V collector-emitter sustaining voltage (V_CEO(sus)), 6 A DC collector current, and 65 W collector dissipation at T_C = 25°C. It serves as a medium-power linear amplifier and switching device in industrial motor drives and DC power supplies.

For engineers reviewing the BD243BTU datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO(sus) = 80 V, h_FE ≥ 30 at I_C = 0.3 A, V_CE(sat) ≤ 1.5 V at I_C = 6 A / I_B = 1 A, and TO-220 thermal performance under continuous conduction.

Technical Context

The BD243BTU operates as a single NPN bipolar junction transistor with fixed emitter-base and collector-base junctions. Its design supports linear amplification with h_FE = 30–15 across I_C = 0.3–3 A and switching operation with V_CE(sat) = 1.5 V at forced β = 6.

Thermal management relies on case-to-ambient conduction via the TO-220 metal tab; derating begins above 25°C case temperature per the published power derating curve. Safe operating area (SOA) is defined up to 10 ms pulse width with 20% duty cycle, limiting simultaneous V_CE and I_C stress.

Key Specifications

Pinout & Package

BD243BTU uses a standard TO-220 package with insulated tab and 3 leads: Base (lead 1), Collector (lead 2), Emitter (lead 3). The metal tab is electrically connected to the collector and must be isolated from chassis ground unless circuit topology requires collector-common mounting.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TIP31C and MJE13003, BD243BTU delivers balanced 6 A/80 V capability with proven thermal performance in TO-220, making it preferable for medium-power linear and switching roles where both current and voltage headroom are required simultaneously.

Availability

BD243BTU is available at Aetrix Electronics and suitable for DC motor control, linear voltage regulation, and switch-mode power supply designs requiring stable component supply and long-term industrial availability.

Supply support for BD243BTU 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in discrete power devices and analog ICs before its acquisition by ON Semiconductor in 2016.

The BD243BTU belongs to Fairchild's legacy BD24x series of medium-power NPN transistors designed for industrial linear amplification and hard-switching applications with emphasis on manufacturability and thermal reliability in TO-220.

FAQ

What is the maximum continuous collector current rating for BD243BTU?

The BD243BTU has a maximum DC collector current rating of 6 A at T_C = 25°C. This rating assumes adequate heatsinking; derating is required above 25°C case temperature per the published power derating curve. At 100°C case temperature, the usable I_C drops to approximately 3.5 A. Always verify thermal design using the BD243BTU's 65 W P_C and R_θJC = 1.92 °C/W values.

Is BD243BTU pin-compatible with BD243B or BD243C?

Yes, BD243BTU shares identical pinout (Base–Collector–Emitter), package (TO-220), and terminal assignments with BD243B and BD243C. The "TU" suffix denotes tape-and-reel packaging; electrical and thermal specifications remain unchanged from the bulk BD243B variant. No PCB layout changes are needed when substituting BD243BTU for BD243B in production.

What is the minimum DC current gain (h_FE) of BD243BTU under typical operating conditions?

The BD243BTU guarantees h_FE ≥ 30 at V_CE = 4 V and I_C = 0.3 A. At higher currents (I_C = 3 A), h_FE drops to ≥15. These values are measured at T_C = 25°C and define base drive requirements for reliable saturation or linear biasing. Designers should use the lower h_FE value for worst-case base resistor calculations.

Does BD243BTU require a heatsink in all applications?

Yes, BD243BTU requires a heatsink whenever power dissipation exceeds ~2–3 W continuously. With P_C = 65 W at T_C = 25°C and R_θJC = 1.92 °C/W, even modest dissipation (e.g., 10 W) raises junction temperature significantly without thermal management. TO-220 mounting hardware and thermal compound are mandatory for sustained operation above ambient-rated power levels.

What is the relationship between BD243BTU and BD244B?

BD243BTU is the NPN complement to the PNP BD244B transistor. Both share matching voltage ratings (80 V), current capability (6 A), and TO-220 packaging, enabling direct use in complementary push-pull output stages without recalculating bias networks. Their matched h_FE and V_CE(sat) characteristics minimize crossover distortion in Class-AB amplifier designs.