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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

onsemi BC548BU

Name: BC548BU
Brand: onsemi
SKU: BC548BU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC548BU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 (TO-226AA)

Datasheet:: BC548BU.pdf

Description:: TRANS NPN 30V 0.1A TO-92-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BC548BU from ON Semiconductor is a general-purpose NPN epitaxial silicon transistor used for low-power switching and linear amplification in discrete analog circuits. It features V_CEO = 30 V, I_C = 100 mA, P_C = 500 mW, h_FE range of 420–800 (Class C), and TO-92 package - commonly deployed in signal conditioning stages of industrial sensor interfaces and consumer audio preamplifiers.

For engineers reviewing the BC548BU datasheet, pinout, applications, or equivalent options, key selection considerations include its DC current gain classification (C-grade), saturation voltage at 10 mA/0.5 mA drive, noise figure at 1 kHz, and compatibility with legacy BC-series designs requiring TO-92 footprint and complementary PNP pairing (e.g., BC558).

Technical Context

The BC548BU operates as a single NPN bipolar junction transistor with epitaxial base construction, optimized for stable h_FE across temperature and low V_CE(sat) in switching mode. Its junction temperature rating of 150°C and storage range of −65°C to +150°C support operation in non-hermetic industrial enclosures.

It exhibits f_T = 300 MHz at V_CE = 5 V, I_C = 10 mA, enabling use in RF front-end biasing and IF amplifier stages up to ~100 MHz. Input capacitance (C_ib = 9 pF) and output capacitance (C_ob = 3.5–6.0 pF) are specified at 1 MHz, confirming suitability for medium-frequency analog signal paths.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	30 V - Maximum collector-emitter voltage before breakdown; sets upper rail limit for common-emitter amplifier stages.
I_C (DC)	100 mA - Continuous collector current rating; defines maximum load drive capability in switching applications.
P_C	500 mW - Total power dissipation at T_A = 25°C; requires thermal derating above 25°C ambient per datasheet curve.
h_FE (Class C)	420–800 - DC current gain range at V_CE = 5 V, I_C = 2 mA; enables high-gain small-signal amplification with predictable bias stability.
V_CE(sat)	90–250 mV @ I_C = 10 mA, I_B = 0.5 mA - Low saturation voltage ensures minimal conduction loss in digital logic interface and relay driver circuits.
f_T	300 MHz - Current gain bandwidth product; supports stable amplification up to ~100 MHz with proper compensation.
NF	2.0–10.0 dB @ V_CE = 5 V, I_C = 200 μA, f = 1 kHz - Noise figure suitable for microphone preamps and sensor signal chains where SNR > 60 dB is required.

Pinout & Package

BC548BU is housed in a JEDEC-standard TO-92 3-lead plastic package with straight leads (bulk packaging). The device uses standard pin configuration: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter - verified per Fairchild/ON Semiconductor mechanical drawings and application schematics.

Pin/Terminal	Circuit Role	Design Meaning
1 (Collector)	Main current output terminal	Connected to load or supply rail; must remain within V_CEO = 30 V and P_C = 500 mW limits during operation.
2 (Base)	Control input for minority carrier injection	Requires current-limited drive (e.g., via 10 kΩ resistor); base-emitter forward voltage is 580–700 mV at I_C = 2 mA.
3 (Emitter)	Current return path and reference node	Typically grounded in common-emitter config; emitter degeneration resistors improve linearity and thermal stability.

Key Features

Feature	Design Value
High DC current gain (h_FE up to 800)	Enables low-base-drive amplifier stages with minimal loading on preceding circuitry (e.g., op-amp outputs or microcontroller GPIOs).
Low V_CE(sat) (as low as 90 mV)	Reduces power loss and heat generation in saturated-switch applications such as LED drivers and logic-level translators.
TO-92 package with industry-standard pinout	Ensures drop-in compatibility with existing BC-series PCB footprints and hand-soldering workflows without layout revision.
Complementary PNP pairing (BC558)	Supports push-pull output stages and differential pair configurations in analog front-ends and discrete power management blocks.
Specified noise figure (2.0–10.0 dB)	Validated for low-noise preamplifier use in audio and precision sensor signal chains where <10 μV RMS input-referred noise is acceptable.

Applications

Audio Preamp Stage	Microcontroller GPIO Driver
Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors before ADC sampling. IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier in common-emitter configuration with emitter degeneration. Use Value: h_FE ≥ 420 and NF ≤ 10.0 dB enable >60 dB SNR at 1 kHz with minimal external components and no active feedback.	Use Scenario: Driving LEDs, relays, or small solenoids from 3.3 V or 5 V microcontroller outputs. IC Role / Device Role / Timing Role: Saturated switch controlled by MCU GPIO with base current limiting. Use Value: V_CE(sat) ≤ 250 mV at I_C = 10 mA ensures <2.5 mW conduction loss and full logic-level compatibility.
Industrial Sensor Interface	Legacy Equipment Repair
Use Scenario: Signal conditioning for RTD or thermistor bridges in programmable logic controller (PLC) analog input modules. IC Role / Device Role / Timing Role: Discrete gain stage in instrumentation amplifier front-end with temperature-stable h_FE. Use Value: Junction temperature rating of 150°C and h_FE consistency over −40°C to +85°C ensure long-term calibration stability.	Use Scenario: Replacement for obsolete BC548 variants in decades-old test equipment, audio gear, and telecom hardware. IC Role / Device Role / Timing Role: Direct-fit discrete transistor maintaining original electrical behavior and mechanical fit. Use Value: Identical TO-92 footprint, pinout, and h_FE classification (C-grade) guarantee zero-change board replacement without requalification.

Audio Preamp Stage

Microcontroller GPIO Driver

Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors before ADC sampling.

IC Role / Device Role / Timing Role: Discrete NPN transconductance amplifier in common-emitter configuration with emitter degeneration.

Use Value: h_FE ≥ 420 and NF ≤ 10.0 dB enable >60 dB SNR at 1 kHz with minimal external components and no active feedback.

Use Scenario: Driving LEDs, relays, or small solenoids from 3.3 V or 5 V microcontroller outputs.

IC Role / Device Role / Timing Role: Saturated switch controlled by MCU GPIO with base current limiting.

Use Value: V_CE(sat) ≤ 250 mV at I_C = 10 mA ensures <2.5 mW conduction loss and full logic-level compatibility.

Industrial Sensor Interface

Legacy Equipment Repair

Use Scenario: Signal conditioning for RTD or thermistor bridges in programmable logic controller (PLC) analog input modules.

IC Role / Device Role / Timing Role: Discrete gain stage in instrumentation amplifier front-end with temperature-stable h_FE.

Use Value: Junction temperature rating of 150°C and h_FE consistency over −40°C to +85°C ensure long-term calibration stability.

Use Scenario: Replacement for obsolete BC548 variants in decades-old test equipment, audio gear, and telecom hardware.

IC Role / Device Role / Timing Role: Direct-fit discrete transistor maintaining original electrical behavior and mechanical fit.

Use Value: Identical TO-92 footprint, pinout, and h_FE classification (C-grade) guarantee zero-change board replacement without requalification.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC548C (ON Semiconductor)	Same die, identical h_FE range (420–800), same TO-92 package and pinout; differs only in packing method (ammo vs bulk).	No functional difference; suitable for automated assembly (tape/reel) or manual prototyping (bulk).	Select BC548BU for hand-soldered prototypes or low-volume repair; BC548CTA for SMT-compatible reel-fed production.
PN2222A (ON Semiconductor)	Higher V_CEO = 40 V, higher I_C = 800 mA, but lower h_FE min = 100; TO-92 package with different pinout (E-B-C vs C-B-E).	Not pin-compatible; requires PCB layout change. Better for higher-current switching but less optimal for low-noise amplification.	Choose PN2222A only when higher voltage/current headroom is needed and board redesign is acceptable.

Compared with BC548C, BC548BU offers identical electrical performance and mechanical fit but in bulk packaging for lab use; versus PN2222A, it trades off current/voltage capability for superior gain consistency and noise performance in low-level analog roles.

Availability

BC548BU is available at Aetrix Electronics and suitable for industrial sensor interfaces, audio preamplifiers, and microcontroller peripheral drivers requiring stable component supply and long-term obsolescence management.

Supply support for BC548BU 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, and cloud infrastructure markets.

The BC548BU belongs to ON Semiconductor's legacy general-purpose transistor portfolio, designed for cost-sensitive, high-reliability discrete signal conditioning and switching in non-critical analog and digital systems.

FAQ

What is the h_FE range for BC548BU?

The BC548BU is classified as a Class C device with a guaranteed DC current gain (h_FE) range of 420 to 800 at V_CE = 5 V and I_C = 2 mA. This high-gain band supports low-base-drive amplifier topologies and improves signal-to-noise ratio in preamplifier stages without requiring additional gain stages. The BC548BU specification matches the original Fairchild BC548C grading.

Is BC548BU pin-compatible with BC547 or BC546?

Yes, BC548BU shares the identical TO-92 package and pinout (Collector-Base-Emitter) with BC546, BC547, BC549, and BC550. However, absolute maximum ratings differ: BC548BU has V_CEO = 30 V and V_CBO = 30 V, whereas BC546 supports up to 65 V V_CEO. Substitution requires verification of voltage stress margins in the target circuit.

What is the maximum operating temperature for BC548BU?

The BC548BU has a maximum junction temperature (T_J) of 150°C and a storage temperature range of −65°C to +150°C. Derating begins above 25°C ambient per the datasheet's thermal resistance curve (R_θJA ≈ 200°C/W), meaning power dissipation must be reduced by ~5 mW/°C above 25°C to maintain safe junction operation.

Does BC548BU support low-noise audio applications?

Yes, BC548BU has a noise figure of 2.0–10.0 dB at V_CE = 5 V, I_C = 200 μA, and f = 1 kHz, making it suitable for electret microphone preamplifiers and sensor signal conditioning where input-referred noise below 10 μV RMS is acceptable. Its performance aligns with BC549/BC550 in low-noise grades but at lower cost.

Can BC548BU replace BC548B or BC548A in existing designs?

Yes - BC548BU is the bulk-packaged version of the BC548C grade transistor. While BC548A (h_FE = 110–220) and BC548B (h_FE = 200–450) offer lower gain, BC548BU's C-grade h_FE (420–800) provides higher amplification and improved consistency. Circuit functionality is preserved, though bias point may shift slightly; verify quiescent operating point if replacing A/B grades.

BC548BU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 (TO-226AA)

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 100 mA

Voltage - Collector Emitter Breakdown (Max):: 30 V

Vce Saturation (Max) @ Ib, Ic:: 600mV @ 5mA, 100mA

Current - Collector Cutoff (Max):: 15nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 110 @ 2mA, 5V

Power - Max:: 500 mW

Frequency - Transition:: 300MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

BC548BU FAQ

1.How can I place an order for BC548BU through Aetrix?

Please submit a Request for Quotation (RFQ) for BC548BU on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for BC548BU reliable?

The price and inventory of BC548BU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC548BU is usually 5 days.

3.What payment methods are accepted for BC548BU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC548BU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC548BU?

BC548BU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC548BU order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for BC548BU?

For technical support, including BC548BU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC548BU requirements.

6.How does Aetrix verify that BC548BU is sourced from the original manufacturer or authorized distributors?

All BC548BU products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BC548BU meets industry standards.

7.What is the process for return or replacement of BC548BU?

All BC548BU units undergo pre-shipment inspection (PSI). If there is an issue with BC548BU, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The BC548BU part is unused and in its original packaging.

Return procedure for BC548BU:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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