onsemi BD243ATU

Overview

BD243ATU from ON Semiconductor (formerly Fairchild) is an NPN epitaxial silicon power transistor in TO-220 package, rated for 60 V V_CEO, 6 A continuous 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 BD243ATU datasheet, pinout, applications, or equivalent options, key selection factors include V_CEO = 60 V, I_C = 6 A, h_FE ≥ 30 @ 0.3 A, V_CE(sat) ≤ 1.5 V @ 6 A/1 A, and TO-220 thermal performance under forced-air or heatsink conditions.

Technical Context

The BD243ATU operates as a medium-power NPN bipolar junction transistor optimized for linear amplification and hard-switching duty. Its 60 V V_CEO rating supports operation in 48 V rail systems, while its 6 A I_C and 65 W P_C enable robust conduction with adequate SOA margin up to 10 ms pulse width.

It features h_FE ≥ 30 at I_C = 0.3 A and ≥15 at I_C = 3 A, V_BE(on) = 2 V @ I_C = 6 A, and V_CE(sat) = 1.5 V @ I_C = 6 A / I_B = 1 A - confirming suitability for base-driven switching where gate drive ICs are not used.

Key Specifications

Pinout & Package

BD243ATU uses the standard TO-220 package with 3 leads: lead 1 = Base, lead 2 = Collector (electrically connected to tab), lead 3 = Emitter. The metal tab is internally tied to the collector and must be electrically isolated from chassis unless collector is at ground potential.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BD243ATU, MJD243G trades mechanical robustness and thermal capacity for surface-mount compatibility, while BD243C extends voltage headroom at minor cost to saturation efficiency - both retain functional equivalence in base-driven switching topologies.

Availability

BD243ATU is available at Aetrix Electronics and suitable for DC motor control, linear voltage regulation, and switch-mode power supply auxiliary circuits requiring stable component supply and long-life industrial availability.

Supply support for BD243ATU 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.

The BD243ATU belongs to Fairchild's legacy BD24x NPN power transistor family, designed specifically for medium-power linear and switching applications where ruggedness, proven SOA, and TO-220 thermal interface are prioritized over ultra-high-speed switching.

FAQ

What is the maximum continuous collector current rating for BD243ATU?

The BD243ATU has a maximum continuous collector current (I_C) rating of 6 A at case temperature T_C = 25°C. Operation above this value requires derating per the power dissipation curve; at T_C = 100°C, the usable I_C drops to approximately 3.5 A due to thermal limits. The BD243ATU must be mounted on an appropriately sized heatsink to sustain rated current.

Is BD243ATU pin-compatible with BD243, BD243B, or BD243C?

Yes, BD243ATU shares identical TO-220 pinout (Base–Collector–Emitter) and mechanical dimensions with BD243, BD243B, and BD243C. However, electrical ratings differ: BD243ATU has V_CEO = 60 V, whereas BD243 is 45 V, BD243B is 80 V, and BD243C is 100 V. Substitution requires verification of voltage stress margins in the target circuit.

What is the typical DC current gain (h_FE) of BD243ATU at operating conditions?

The BD243ATU exhibits h_FE ≥ 30 at V_CE = 4 V and I_C = 0.3 A, and h_FE ≥ 15 at V_CE = 4 V and I_C = 3 A. This gain profile supports stable linear operation across mid-range currents and confirms adequate drive capability for base-resistor-controlled switching. The BD243ATU data sheet specifies these values under standardized test conditions.

Does BD243ATU have a built-in base-emitter resistor or protection diode?

No, BD243ATU is a discrete NPN bipolar transistor with no integrated base-emitter resistor or protection diode. External components - such as a base current-limiting resistor and optional BE clamp diode - must be added per application requirements. This design preserves flexibility for both linear and switching use cases, consistent with the BD243ATU's role as a general-purpose power transistor.

What thermal resistance (R_θJC) does BD243ATU exhibit in TO-220 package?

The BD243ATU has a junction-to-case thermal resistance (R_θJC) of 1.9°C/W, derived from its 65 W power dissipation rating and 150°C maximum junction temperature. This value assumes full contact between the metal tab and heatsink with thermal compound; actual system R_θJA depends on heatsink size, airflow, and mounting quality. The BD243ATU's TO-220 package enables repeatable thermal performance in production assemblies.