onsemi BUD43B

Overview

BUD43B from onsemi is an NPN silicon planar power transistor designed for high-voltage switching in 220 V line-operated switchmode power supplies and electronic ballasts. It features a 350 V_CEO, 2 A continuous collector current, 25 W total device dissipation at T_C = 25°C, V_CE(sat) = 1 V (IC = 2 A, IB = 0.5 A), and h_FE ≥ 6 at IC = 2 A - enabling efficient, low-loss operation in compact lighting and SMPS designs.

For engineers reviewing the BUD43B datasheet, pinout, applications, or equivalent options, key selection considerations include its 650 V_VCES rating, fast 4.7–5.8 μs turn-off time, DPAK (CASE 369-07) surface-mount package, and suitability for high-reliability electronic ballast and offline SMPS primary-side switching.

Technical Context

The BUD43B is a discrete NPN bipolar junction transistor optimized for hard-switched, high-voltage applications where low base drive requirements and tight switching distribution are critical. Its state-of-the-art die delivers flat DC current gain (h_FE ≥ 6 up to 2 A) and eliminates need for base coil during turn-off - reducing component count and improving reliability in ballast and SMPS control stages.

It operates with V_CEO = 350 V, V_CES = 650 V, and V_EBO = 9 V, supporting robust blocking capability across full mains voltage transients. Thermal resistance R_θJC = 5°C/W enables effective heatsinking in constrained industrial lighting modules.

Key Specifications

Pinout & Package

The BUD43B is housed in a surface-mount DPAK package (CASE 369−07), featuring three terminals: Emitter (pin 1), Base (pin 2), Collector (pin 3). The package includes a large exposed collector tab (pin 4) for thermal and electrical connection to PCB ground plane or heatsink.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN high-voltage switching transistor applications.

Compared with MJD44H11T4 and BUL49D, the BUD43B offers optimal balance of 2 A current capability, DPAK surface-mount compatibility, and 350 V_CEO rating for compact 25–40 W electronic ballast and adapter designs - minimizing PCB area while maintaining thermal and surge robustness.

Availability

BUD43B is available at Aetrix Electronics and suitable for compact fluorescent ballasts, LED driver primary switches, and 25–40 W AC-DC adapters requiring stable component supply, consistent parametric performance, and long-term industrial availability.

Supply support for BUD43B 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

onsemi (formerly ON Semiconductor) is a global semiconductor manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and IoT applications.

The BUD43B belongs to onsemi's SWITCHMODE™ planar bipolar transistor product line, engineered specifically for high-reliability, high-voltage switching in electronic lighting and offline power conversion systems.

FAQ

What is the maximum operating temperature for the BUD43B?

The BUD43B has a specified operating junction temperature range of –65°C to +150°C. This wide range supports deployment in thermally demanding environments such as enclosed LED luminaires and industrial control cabinets. Derating of power dissipation begins above 25°C ambient, with thermal resistance R_θJC = 5°C/W enabling predictable thermal design when mounted to appropriate copper area. The BUD43B must be operated within this limit to maintain reliability and parameter stability.

Does the BUD43B require a base coil for turn-off?

No, the BUD43B does not require a base coil for fast turn-off. Its application-specific die design eliminates current tail and enables clean switching without external base inductance. This feature simplifies driver circuitry, reduces component count, and improves timing consistency in electronic ballast and SMPS applications. The BUD43B achieves 4.7–5.8 μs turn-off time using only resistive base drive, as confirmed in the official onsemi datasheet for BUD43B.

What package type is used for the BUD43B?

The BUD43B uses the DPAK surface-mount package (CASE 369−07), which features three signal leads and an exposed collector tab (pin 4) for thermal and electrical connection. This package supports automated assembly and provides low thermal resistance (R_θJC = 5°C/W) when soldered to a minimum 1.8″ × 0.070″ copper pad. The BUD43B's mechanical dimensions and soldering profile comply with JEDEC standards for DPAK devices.

Can the BUD43B replace the BUD42B in existing designs?

Yes, the BUD43B is a direct upgrade to the BUD42B, offering improved efficiency via lower base drive requirements and tighter switching distributions. Both share identical DPAK packaging, pinout, and thermal characteristics. Key improvements in the BUD43B include enhanced h_FE flatness and reduced V_CE(sat), resulting in lower conduction loss. No PCB changes are required when substituting BUD43B for BUD42B in validated designs.

What is the V_CE(sat) specification for the BUD43B at rated current?

The BUD43B specifies V_CE(sat) ≤ 1 Vdc at I_C = 2 Adc and I_B = 0.5 Adc, measured at T_C = 25°C. This low saturation voltage directly reduces conduction losses and thermal loading in continuous-duty applications like electronic ballasts. The value remains stable across production lots due to the device's state-of-the-art die process, making the BUD43B suitable for high-efficiency, thermally constrained designs.