onsemi BC238CBU

Overview

BC238CBU from Fairchild Semiconductor is an NPN epitaxial silicon transistor optimized for low-noise amplifier and general-purpose switching applications, with V_CEO = 25 V, I_C = 100 mA, P_C = 500 mW, h_FE = 380–800 (Class C), and f_T = 85 MHz at V_CE = 5 V, I_C = 10 mA - deployed in audio preamplifiers, signal conditioning stages, and discrete logic interface circuits.

For engineers reviewing the BC238CBU datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package compatibility, Class C h_FE gain band, low V_CE(sat) (0.2 V typ. @ I_C = 10 mA), noise figure of 4 dB at 1 kHz, and verified suitability for linear amplification and saturated switching in cost-sensitive analog and mixed-signal designs.

Technical Context

The BC238CBU operates as a discrete NPN bipolar junction transistor with epitaxial base construction enabling stable DC current gain and improved high-frequency response. Its design supports both linear amplification (V_CE = 5 V, I_C = 2 mA) and hard-switching (I_C = 100 mA, I_B = 5 mA), with V_BE(on) = 0.62 V typical and Cob = 3.5–6 pF ensuring predictable AC coupling behavior.

It belongs to the BC237/238/239 family sharing identical TO-92 mechanical outline and pinout (Emitter-Base-Collector), but differentiated by voltage ratings (V_CEO = 25 V), h_FE classification (Class C), and noise performance (NF = 4 dB), making it distinct from BC237A/B and BC239 variants in gain-bandwidth and low-noise trade-offs.

Key Specifications

Pinout & Package

BC238CBU is housed in a standard through-hole TO-92 package (3.60 × 4.58 × 14.47 mm), with lead material compliant to RoHS requirements and JEDEC registered outline.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547C and PN2222A, BC238CBU offers superior low-noise performance (4 dB vs. ≥5 dB) and tighter h_FE consistency for precision amplification, while trading off voltage headroom and absolute power rating - optimal where signal integrity and gain predictability outweigh raw voltage or thermal margins.

Availability

BC238CBU is available at Aetrix Electronics and suitable for audio pre-amplifier stages, discrete logic level shifters, linear voltage regulator pass elements, and LED driver switches requiring stable component supply across prototyping, industrial control, and consumer electronics production.

Supply support for BC238CBU 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 BC238CBU belongs to Fairchild's legacy general-purpose bipolar transistor product line, designed specifically for cost-sensitive, high-reliability analog signal conditioning and switching in consumer, industrial, and communications equipment.

FAQ

What is the pin configuration of BC238CBU?

The BC238CBU uses a standard TO-92 package with pinout: Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector. This configuration is consistent across the BC237/238/239 family and matches JEDEC TO-92 mechanical specifications. Always verify orientation using the flat side and lead-down view per Fairchild's datasheet diagram - incorrect mounting may reverse polarity and cause circuit failure. The BC238CBU pinout is not interchangeable with PN2222A or BC547C without layout verification.

What does the 'C' suffix in BC238CBU indicate?

The 'C' in BC238CBU denotes h_FE classification - specifically, a guaranteed DC current gain range of 380 to 800 at V_CE = 5 V and I_C = 2 mA. The 'BU' suffix indicates the TO-92 package variant with lead finish compliant to RoHS requirements. This binning ensures predictable biasing in amplifier designs without manual gain sorting, distinguishing BC238CBU from BC238A (120–220) and BC238B (180–460).

Can BC238CBU replace BC239 in low-noise applications?

No - BC239 has a lower specified noise figure (2 dB vs. BC238CBU's 4 dB) and is explicitly optimized for ultra-low-noise amplification per Fairchild's datasheet. While both share V_CEO = 25 V and TO-92 packaging, BC238CBU's 4 dB NF meets general-purpose audio requirements but falls short of BC239's performance in sensitive microphone or instrumentation front-ends. For such cases, BC239 remains the preferred choice; BC238CBU is better suited for non-critical gain stages.

What is the maximum operating temperature for BC238CBU?

The BC238CBU has a maximum junction temperature (T_J) of 150°C and a storage temperature range of –55°C to +150°C. In practice, sustained operation above 125°C requires thermal derating per the datasheet's power dissipation curve - at 70°C ambient, maximum allowable P_C drops to ~350 mW. PCB copper area, airflow, and enclosure design directly impact real-world thermal performance of the BC238CBU.

Is BC238CBU suitable for switching power supply applications?

The BC238CBU is not recommended for primary switching in SMPS due to limited f_T (85 MHz), moderate Cob (3.5–6 pF), and absence of avalanche-rated ruggedness. It can serve in auxiliary functions - e.g., optocoupler driver or feedback comparator stage - where switching frequencies remain below 500 kHz and voltage stress stays under 25 V. For main switch roles, dedicated power transistors like MMBT2222A or MOSFETs offer superior efficiency and reliability compared to BC238CBU.