onsemi BC547BU

Overview

BC547BU from ON Semiconductor is a general-purpose NPN epitaxial silicon transistor used for low-power switching and amplification in discrete analog and digital circuits. It features V_CEO = 45 V, I_C = 100 mA, P_C = 500 mW, h_FE range of 110–800 (depending on grade), and TO-92 package. It is commonly deployed in signal conditioning stages of sensor interfaces and low-voltage logic-level translation.

For engineers reviewing the BC547BU datasheet, pinout, applications, or equivalent options, key selection considerations include DC current gain classification (A/B/C), saturation voltage at defined I_C/I_B, noise figure (especially for audio preamp use), and thermal derating above 25°C ambient.

Technical Context

The BC547BU operates as a bipolar junction transistor with epitaxial base construction, enabling stable h_FE across temperature and improved high-frequency response up to f_T = 300 MHz. Its low V_BE(on) (580–700 mV at I_C = 2 mA) supports reliable turn-on in 3.3 V and 5 V logic-driven switch designs.

It is rated for V_CBO = 50 V and V_EBO = 6 V, with collector cut-off current I_CBO ≤ 15 nA at V_CB = 30 V - indicating low leakage suitable for battery-powered standby circuits. The device is not optimized for RF power amplification but supports small-signal amplification up to mid-VHF.

Key Specifications

Pinout & Package

BC547BU is housed in a JEDEC TO-92 3-lead plastic package with straight leads (bulk configuration). Pin 1 is Collector, Pin 2 is Base, Pin 3 is Emitter - verified per Fairchild/ON Semiconductor mechanical drawings and ordering information tables.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547BTA and 2N3904, the BC547BU offers identical performance to BC547BTA in bulk form and provides 5 V higher V_CEO than 2N3904 - making it preferable for 48 V-tolerant auxiliary rails or designs requiring extra voltage safety margin without changing layout.

Availability

BC547BU is available at Aetrix Electronics and suitable for audio preamplifiers, microcontroller interface drivers, and linear regulator pass elements requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for BC547BU 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 (formerly Fairchild Semiconductor) is a global supplier of energy-efficient semiconductor components focused on power management, analog, sensing, and connectivity solutions.

The BC547BU belongs to the BC546–BC550 NPN transistor family designed for cost-sensitive, high-volume general-purpose amplification and switching in consumer, industrial, and automotive-qualified auxiliary circuits.

FAQ

What is the maximum collector-emitter voltage rating for BC547BU?

The BC547BU has a maximum collector-emitter voltage (V_CEO) rating of 45 V at T_A = 25°C. This rating decreases with rising ambient temperature and must be derated per the datasheet's thermal curves. Exceeding this limit risks avalanche breakdown and permanent device failure. Always verify operating conditions using the absolute maximum ratings table in the official BC547BU datasheet.

Does BC547BU have a specified noise figure, and how does it vary by grade?

Yes, BC547BU has a noise figure (NF) of 2.0–10.0 dB at V_CE = 5 V, I_C = 200 μA, f = 1 kHz, and R_G = 2 kΩ. This range applies to the BC547 variant (not BC549/BC550). Lower NF values correlate with higher h_FE grades (e.g., C-grade typically exhibits better noise performance than A-grade), though exact NF per grade is not binned - design margin must account for the full 2–10 dB span.

What is the pin configuration of BC547BU, and how is it verified?

The BC547BU uses a standard TO-92 package with pinout: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter - confirmed by Fairchild Semiconductor's original BC546–BC550 datasheet Rev. 1.1.1, Figure 7 (bulk-type mechanical drawing), and ON Semiconductor's cross-reference documentation. This configuration is consistent across all BC546–BC550 variants and matches industry-standard TO-92 orientation when flat side faces viewer and leads point downward.

Can BC547BU replace BC547B in existing designs without modification?

Yes, BC547BU is functionally and physically identical to BC547B - both share the same die, TO-92 package, electrical specifications, and pinout. The "BU" suffix denotes bulk packaging (vs. "BTA" for ammo or "BTF" for tape-and-reel), so PCB layout, schematic symbol, and circuit operation remain unchanged. No redesign or revalidation is needed beyond verifying packaging logistics for assembly.

What h_FE range does BC547BU support, and how is it classified?

BC547BU supports h_FE classifications A (110–220), B (200–450), and C (420–800) - determined during final test and marked accordingly (e.g., "BC547B" marking indicates B-grade). The specific h_FE of a given BC547BU unit falls within its marked grade band. Designers must select base biasing to accommodate the full min–max range of the chosen grade to ensure robust saturation or linear operation across manufacturing variance.