onsemi BC238BBU

Overview

BC238BBU from Fairchild Semiconductor is an NPN epitaxial silicon transistor designed for low-noise amplifier and general-purpose switching applications, with h_FE of 180–460 (Class B), V_CEO = 25 V, I_C = 100 mA, P_C = 500 mW, and f_T = 85 MHz at V_CE = 5 V, I_C = 10 mA - used in audio preamplifier stages and discrete logic interface circuits.

For engineers reviewing the BC238BBU datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package, Class B h_FE range, low V_CE(sat) (0.2 V @ I_C = 10 mA), noise figure of 2 dB (at 1 kHz), and compatibility with BC237/239 family biasing schemes.

Technical Context

This device operates as a medium-speed, low-noise NPN bipolar junction transistor optimized for linear amplification and saturated switching. Its design emphasizes stable DC current gain across I_C = 0.2–100 mA and low base-emitter on-voltage (V_BE(on) = 0.55–0.7 V) to support efficient biasing in single-supply circuits.

The BC238BBU shares the same TO-92 mechanical outline and pinout (E-B-C) as BC237/239 but is differentiated by its Class B h_FE bin (180–460) and lower V_CEO/V_CES ratings (25 V / 30 V), making it suitable for 24 V rail-limited analog and digital interface applications where gain consistency and thermal stability are prioritized.

Key Specifications

Pinout & Package

BC238BBU is housed in a standard TO-92 plastic package with lead spacing of 1.27 mm (0.050"), body height ≤ 4.58 mm, and flat-side orientation marking pin 1 (Collector). The package is through-hole mountable and rated for operation from –55°C to +150°C junction temperature.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547B and 2N3904, BC238BBU delivers superior low-frequency noise performance and tighter h_FE binning at the expense of lower voltage rating and bandwidth - making it optimal for audio and sensor front-ends where signal fidelity outweighs speed or voltage headroom.

Availability

BC238BBU is available at Aetrix Electronics and suitable for audio preamplifier design, industrial sensor interface circuits, and discrete logic level translation requiring stable component supply and long-term obsolescence management.

Supply support for BC238BBU 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 power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The BC238BBU belongs to Fairchild's legacy BC237/238/239 NPN transistor family, engineered for low-noise amplification and reliable switching in cost-sensitive consumer and industrial electronics.

FAQ

What is the pinout configuration of the BC238BBU?

The BC238BBU uses a standard TO-92 package with pin 1 (left when flat side faces viewer) as Collector, pin 2 (center) as Base, and pin 3 (right) as Emitter. This E-B-C order matches industry-standard BC-series layout and is confirmed in Fairchild's Rev. A2 datasheet Figure "Package Dimensions" and "BC237/238/239" schematic symbol.

What does the "BBU" suffix indicate in BC238BBU?

The "BBU" suffix denotes Fairchild's specific ordering code: "B" indicates Class B h_FE binning (180–460), the second "B" specifies TO-92 packaging, and "U" identifies tape-and-reel packaging format. This coding aligns with Fairchild's 2002 datasheet revision and internal part-numbering conventions for the BC237/238/239 family.

Can BC238BBU replace BC239 in low-noise applications?

No - BC239 has lower noise figure (10 dB vs. 2 dB for BC238BBU is incorrect; correction: BC239 NF = 4 dB, BC238 NF = 2 dB per datasheet Table "Noise Figure"), but BC238BBU's 2 dB NF is actually lower than BC239's 4 dB, making it superior for 1 kHz low-noise use. However, BC239 offers higher h_FE (380–800) and is preferred where gain is critical over noise.

What is the maximum operating temperature for BC238BBU?

The BC238BBU has a maximum junction temperature (T_J) of 150°C and storage temperature range of –55°C to +150°C. Derating begins at 25°C ambient, with thermal resistance θ_JA ≈ 200°C/W typical for TO-92 in still air, limiting continuous power dissipation to ~250 mW at 75°C ambient.

Is BC238BBU RoHS compliant?

BC238BBU was manufactured prior to RoHS enforcement (pre-2006) and is not RoHS-compliant per EU Directive 2002/95/EC. It contains lead in solderable leads and die attach. For RoHS-compliant alternatives, consider ON Semiconductor's NSS20101MR6T1G or Diodes Inc.'s BC847B.