onsemi BD441

Overview

BD441 from ON Semiconductor is a medium-power NPN epitaxial silicon transistor designed for linear amplification and switching applications in industrial power supplies and motor control circuits, with V_CEO = 80 V, I_C = 4 A, P_C = 36 W at T_C = 25°C, h_FE ≥ 40 (I_C = 10 mA, V_CE = 5 V), and V_CE(sat) ≤ 0.5 V (I_C = 2 A, I_B = 0.2 A).

For engineers reviewing the BD441 datasheet, pinout, applications, or equivalent options, this page delivers verified electrical ratings, TO-126 package layout, complementary pairing context (vs. BD442), safe operating area limits, and real-world use cases in DC-DC converter output stages and relay drivers.

Technical Context

The BD441 operates as a single NPN bipolar junction transistor optimized for medium-current switching and analog amplification, featuring epitaxial base construction for improved gain consistency and thermal stability. Its rugged SOA supports pulsed collector currents up to 7 A with defined derating above 25°C case temperature.

It is explicitly specified for use with complementary PNP devices BD442 (V_CEO = 80 V) in push-pull and Class AB amplifier configurations. Electrical test conditions are standardized per JEDEC JESD22-A108, with pulse testing limited to PW ≤ 300 μs and duty cycle ≤ 1.5%.

Key Specifications

Pinout & Package

BD441 is housed in a TO-126 plastic package with integral metal tab for mechanical mounting and thermal conduction. The package meets JEDEC TO-126 standard dimensions (12.7 mm × 10.16 mm × 4.57 mm) and features internal leadframe plating compatible with Pb-free reflow soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD44H11 and BD139, BD441 offers balanced through-hole manufacturability, 4 A/36 W capability, and documented pulsed SOA-making it optimal for industrial control boards requiring field-serviceable replacement and proven thermal performance at moderate cost.

Availability

BD441 is available at Aetrix Electronics and suitable for industrial power supplies, motor control modules, and relay interface boards requiring stable component supply, long-term lifecycle support, and RoHS-compliant through-hole transistors.

Supply support for BD441 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 manufacturer specializing in energy-efficient power management, analog, sensor, and logic solutions for automotive, industrial, cloud computing, and consumer markets.

BD441 belongs to ON Semiconductor's legacy bipolar power transistor family, originally developed by Fairchild Semiconductor for robust, cost-effective medium-power linear and switching applications in industrial automation and power conversion.

FAQ

What is the maximum continuous collector current rating for BD441?

The BD441 has a maximum continuous collector current (I_C) rating of 4 A at case temperature T_C = 25°C. This rating assumes adequate heatsinking; derating is required above 25°C per the published power derating curve. At T_C = 100°C, the usable I_C drops to approximately 2.2 A. The BD441 datasheet specifies this value under JEDEC test conditions and confirms it across multiple production lots.

Does BD441 have a complementary PNP transistor, and what is its part number?

Yes, BD441 is explicitly paired with the PNP transistor BD442. Both share identical V_CEO = 80 V, TO-126 packaging, and matched gain/switching characteristics, enabling symmetrical push-pull and Class AB amplifier designs. The BD441/BD442 pair is referenced in Fairchild's original BD433/435/437 family documentation as a designated complementary set.

What is the safe operating area (SOA) behavior of BD441 under pulsed conditions?

The BD441 SOA is fully characterized for both DC and pulsed operation, with pulse limits defined for durations ≤10 ms and duty cycles ≤1.5%. At V_CE = 40 V, it supports up to 4 A pulsed current; at V_CE = 20 V, up to 7 A is permitted. These boundaries are plotted in Figure 5 of the BD433/435/437 datasheet, which applies identically to BD441 per Fairchild's family specification alignment.

Can BD441 be used in audio amplifier output stages, and what gain bandwidth supports that?

Yes, BD441 is suitable for linear audio output stages due to its f_T = 3 MHz and epitaxial base structure, which ensures stable h_FE and low distortion across the 20 Hz–20 kHz band. It is commonly deployed in Class AB emitter-follower configurations with BD442, where its h_FE ≥ 40 at I_C = 10 mA enables precise bias control and thermal tracking.

What package type and pin configuration does BD441 use?

BD441 uses the TO-126 plastic package with three leads: Pin 1 = Emitter, Pin 2 = Collector (connected to metal tab), Pin 3 = Base. The metal tab is electrically connected to the collector and must be isolated from other potentials unless intentional collector-to-heatsink connection is required. Dimensions conform to JEDEC TO-126 standard (12.7 mm × 10.16 mm × 4.57 mm).