onsemi BC338BU

Overview

BC338BU from ON Semiconductor is a general-purpose NPN epitaxial silicon transistor in TO-92 package, rated for 30 V V_CEO, 800 mA I_C, 625 mW P_D, and 100 MHz f_T, commonly used in low-power switching and audio amplifier stages such as AF driver circuits.

For engineers reviewing the BC338BU datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, TO-92 terminal mapping, h_FE classification (25), thermal resistance (200 °C/W), and direct alternatives for discrete BJT replacement in cost-sensitive consumer and industrial signal-path designs.

Technical Context

The BC338BU operates as a medium-current, low-voltage NPN bipolar junction transistor with DC current gain h_FE of 160–400 at I_C = 100 mA and V_CE = 1 V, and saturation voltage V_CE(sat) ≤ 0.7 V at I_C = 500 mA / I_B = 50 mA. Its 12 pF Cob and 100 MHz f_T support audio-frequency amplification and digital switching up to ~10 MHz.

Designed for complementary pairing with BC328 PNP transistors, it supports Class A/B amplifier output stages and discrete logic-level switching. Junction temperature rating of 150 °C and storage range of −55 to +150 °C enable use in non-automotive industrial environments with moderate thermal cycling.

Key Specifications

Pinout & Package

BC338BU is housed in a standard JEDEC TO-92 plastic package with straight leads and bulk packing. The device uses a fixed 3-terminal configuration with emitter, base, and collector arranged in linear order.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC338-25 and PN2222A, BC338BU offers guaranteed h_FE classification (160–400), optimized V_CE(sat) for audio drivers, and bulk packaging for rapid evaluation-making it the preferred choice for cost-sensitive, low-power linear and switching applications demanding predictable gain and thermal behavior.

Availability

BC338BU is available at Aetrix Electronics and suitable for audio frequency driver stages, low-power switching circuits, complementary amplifier designs, and signal-level translation applications requiring stable component supply and long-term obsolescence management.

Supply support for BC338BU 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 power management, analog, sensor, and discrete solutions for automotive, industrial, cloud, and consumer markets.

The BC338BU belongs to ON Semiconductor's legacy general-purpose BJT family, originally developed by Fairchild Semiconductor to deliver reliable, cost-effective NPN switching and amplification for mass-market electronics.

FAQ

What is the maximum collector-emitter voltage rating for BC338BU?

The BC338BU has a maximum collector-emitter voltage (V_CEO) rating of 25 V under open-base conditions at T_A = 25 °C. This value is confirmed in the Absolute Maximum Ratings table of the official BC337/BC338 datasheet Rev. 1.5. Exceeding this voltage risks avalanche breakdown and permanent device damage, so design margins should keep operating V_CE below 20 V in production circuits using BC338BU.

Does BC338BU have a specified h_FE classification, and what is its range?

Yes, BC338BU is classified as h_FE Class 25, with a guaranteed DC current gain range of 160 to 400 at V_CE = 1 V and I_C = 100 mA. This classification is explicitly defined in the Electrical Characteristics table of the BC337/BC338 datasheet and distinguishes BC338BU from unclassified variants like generic BC338 or BC338-25 without suffix marking.

What is the thermal resistance (R_θJA) of BC338BU, and how does it affect PCB layout?

The BC338BU has a junction-to-ambient thermal resistance (R_θJA) of 200 °C/W under standard FR-4 PCB conditions (76 mm × 114 mm, minimum land pattern). This means a 625 mW power dissipation at 25 °C ambient raises junction temperature by 125 °C - reaching the 150 °C limit. To maintain reliability, PCB copper area around the emitter pad must be maximized, and continuous power should stay below 350 mW at 70 °C ambient when using BC338BU.

Can BC338BU be used as a direct replacement for BC337 in existing designs?

No, BC338BU is not a direct replacement for BC337 due to key parameter differences: BC338BU has V_CEO = 25 V and V_CES = 30 V, while BC337 offers V_CEO = 45 V and V_CES = 50 V. Substituting BC338BU in a BC337 design risks premature breakdown if collector voltage exceeds 25 V. Always verify voltage stress margins before interchanging BC337 and BC338BU in the same schematic.

What is the typical transition frequency (f_T) of BC338BU, and how is it measured?

The BC338BU has a typical current gain bandwidth product (f_T) of 100 MHz, measured at V_CE = 5 V, I_C = 10 mA, and f = 50 MHz according to the official BC337/BC338 datasheet. This f_T value indicates the frequency at which short-circuit current gain drops to unity, confirming BC338BU's suitability for audio amplification and digital switching up to ~10 MHz with adequate gain margin.