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

onsemi BC556BU

Name: BC556BU
Brand: onsemi
SKU: BC556BU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC556BU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC556BU.pdf

Description:: TRANS PNP 65V 0.1A TO-92-3

Quantity:: RFQ Add To RFQ list

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Inventory:5,499

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Product details

Overview

BC556BU from onsemi is a PNP epitaxial silicon transistor designed for general-purpose switching and linear amplification in low-power analog and digital circuits. It features V_CEO = −65 V, I_C = −100 mA, h_FE = 110–800 (Class B), f_T = 150 MHz, and TO-92-3 (Case 135AN) packaging. It serves as a high-voltage complement to BC546–BC550 NPN transistors in bias networks, signal inversion stages, and discrete logic interfaces.

For engineers reviewing the BC556BU datasheet, pinout, applications, or equivalent options, key selection criteria include verified V_CEO rating, h_FE classification consistency, saturation voltage at defined I_C/I_B, thermal derating behavior, and Pb-free RoHS-compliant packaging compatibility with through-hole assembly processes.

Technical Context

The BC556BU operates as a medium-speed, medium-voltage PNP bipolar junction transistor optimized for DC-coupled amplification and saturated switching. Its h_FE range (200–450 for Class B) supports stable biasing across temperature, while V_CE(sat) ≤ −300 mV at I_C = −10 mA / I_B = −0.5 mA ensures low conduction loss in active-low switch configurations.

Thermal performance is defined by R_JA = 250 °C/W (FR-4 PCB, 76 mm × 114 mm), with linear derating of 4.0 mW/°C above 25 °C. Its Cob = 6 pF at V_CB = −10 V enables use in audio-frequency amplifiers and low-speed digital interfaces without significant capacitive loading.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−65 V - Supports operation in negative-rail circuits up to 65 V, e.g., industrial sensor biasing or relay drivers with elevated supply rails.
I_C (DC)	−100 mA - Enables direct drive of small solenoids, LEDs, or logic inputs without external current gain staging.
h_FE (Class B)	200–450 - Ensures predictable base current requirements for stable DC bias design across production lots and temperature.
V_CE(sat)	−300 mV max @ I_C = −10 mA / I_B = −0.5 mA - Minimizes power dissipation and voltage drop in saturated switch applications.
f_T	150 MHz - Permits use in audio preamplifiers and low-frequency RF stages (e.g., IF amplification up to ~10 MHz).
C_ob	6 pF @ V_CB = −10 V - Limits high-frequency feedback and maintains stability in common-emitter amplifier topologies.
P_D	500 mW @ T_A = 25°C - Allows continuous operation at full current under moderate ambient conditions with standard PCB copper area.

Pinout & Package

BC556BU is housed in a TO-92-3 plastic package (Case 135AN), with leads arranged in straight-lead configuration. The package measures 4.825 mm × 4.76 mm and is RoHS-compliant, Pb-free, and halogen-free.

Pin/Terminal	Circuit Role	Design Meaning
1	Collector	Primary current sink node; connected to most negative potential in PNP operation; requires heatsinking consideration at >100 mW dissipation.
2	Base	Control input; requires current-limiting resistor to set operating point; sensitive to ESD due to thin oxide layer.
3	Emitter	Current source terminal; typically tied to circuit ground or positive rail depending on topology; defines reference for V_BE and V_CE.

Key Features

Feature	Design Value
High-voltage PNP architecture	V_CEO = −65 V enables robust operation in negative-supply systems where lower-voltage PNP devices would break down.
Low-noise amplification capability	NF = 2–10 dB @ 1 kHz supports clean signal amplification in microphone preamps and sensor front-ends.
Complementary pairing with BC546–BC550 series	Matched h_FE ranges and thermal coefficients allow balanced push-pull stage design in Class A/B audio outputs.
Pb-free, RoHS-compliant construction	Meets global environmental compliance mandates without requiring process requalification for legacy through-hole manufacturing lines.

Applications

Audio Signal Amplification	Discrete Logic Level Shifting
Use Scenario: Low-noise preamplifier stage for electret condenser microphones in portable voice recorders. IC Role / Device Role / Timing Role: PNP common-emitter amplifier providing 20–40 dB voltage gain with minimal added noise. Use Value: NF = 2–10 dB and h_FE ≥ 200 ensure high signal-to-noise ratio and stable gain over battery discharge cycles.	Use Scenario: Inverting level translator between 5 V TTL logic and −5 V analog control bus in test equipment. IC Role / Device Role / Timing Role: Saturated PNP switch converting positive logic highs to negative rail activation signals. Use Value: V_CE(sat) ≤ −300 mV guarantees reliable turn-on margin and fast edge response under load.
Industrial Sensor Biasing	Relay Driver Interface
Use Scenario: Constant-current bias source for RTD or thermistor bridges in programmable logic controller (PLC) analog input modules. IC Role / Device Role / Timing Role: Emitter-follower configured transistor delivering stable −1–2 mA bias current independent of supply variation. Use Value: V_CEO = −65 V accommodates wide-range industrial supplies (e.g., −24 V to −48 V) without derating.	Use Scenario: Direct drive of 12 V/400 Ω electromagnetic relay coil in HVAC control panels. IC Role / Device Role / Timing Role: Saturated switch sinking relay current through collector to ground, with base driven by microcontroller GPIO. Use Value: I_C = −100 mA rating exceeds typical relay hold current (≈80 mA), ensuring long-term reliability.

Audio Signal Amplification

Discrete Logic Level Shifting

Use Scenario: Low-noise preamplifier stage for electret condenser microphones in portable voice recorders.

IC Role / Device Role / Timing Role: PNP common-emitter amplifier providing 20–40 dB voltage gain with minimal added noise.

Use Value: NF = 2–10 dB and h_FE ≥ 200 ensure high signal-to-noise ratio and stable gain over battery discharge cycles.

Use Scenario: Inverting level translator between 5 V TTL logic and −5 V analog control bus in test equipment.

IC Role / Device Role / Timing Role: Saturated PNP switch converting positive logic highs to negative rail activation signals.

Use Value: V_CE(sat) ≤ −300 mV guarantees reliable turn-on margin and fast edge response under load.

Industrial Sensor Biasing

Relay Driver Interface

Use Scenario: Constant-current bias source for RTD or thermistor bridges in programmable logic controller (PLC) analog input modules.

IC Role / Device Role / Timing Role: Emitter-follower configured transistor delivering stable −1–2 mA bias current independent of supply variation.

Use Value: V_CEO = −65 V accommodates wide-range industrial supplies (e.g., −24 V to −48 V) without derating.

Use Scenario: Direct drive of 12 V/400 Ω electromagnetic relay coil in HVAC control panels.

IC Role / Device Role / Timing Role: Saturated switch sinking relay current through collector to ground, with base driven by microcontroller GPIO.

Use Value: I_C = −100 mA rating exceeds typical relay hold current (≈80 mA), ensuring long-term reliability.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC557BTA	V_CEO = −45 V; same h_FE Class B (200–450); identical TO-92-3 (135AR) package but bent-lead form.	Limited to ≤45 V negative-rail systems; not suitable for 65 V designs such as telecom line interface cards.	Select BC557BTA only when supply voltage is confirmed ≤45 V and bent-lead assembly is required.
MMBT5551	NPN polarity; V_CEO = 160 V; SOT-23 package; h_FE = 80–250; not complementary to BC546–BC550 series.	Requires circuit topology redesign (e.g., inverting stage insertion); unsuitable for direct replacement in existing PNP-based layouts.	Use MMBT5551 only in new NPN-centric designs demanding higher voltage tolerance and surface-mount compatibility.

Compared with BC556BU, BC557BTA offers identical gain and noise performance but reduced voltage rating, while MMBT5551 provides superior voltage handling in a different polarity and footprint-neither is pin-compatible, and both require schematic and layout revision.

Availability

BC556BU is available at Aetrix Electronics and suitable for industrial sensor biasing, audio preamplification, discrete logic level translation, and relay driver interface applications requiring stable component supply and legacy through-hole compatibility.

Supply support for BC556BU 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensing, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The BC556BU belongs to the BC556–BC560 family of general-purpose PNP transistors engineered for cost-sensitive, high-reliability through-hole applications in analog signal conditioning, discrete switching, and complementary amplifier stages.

FAQ

What is the maximum collector-emitter voltage rating for BC556BU?

The BC556BU has a guaranteed V_CEO rating of −65 V at T_A = 25°C. This rating applies under DC conditions and must be derated linearly above 25°C per the device's thermal characteristics. Exceeding this voltage risks permanent breakdown, especially in circuits with inductive loads or transient spikes. Always verify operating margin against worst-case supply and flyback conditions when using BC556BU in high-voltage designs.

Is BC556BU RoHS-compliant and lead-free?

Yes, BC556BU is explicitly marked as Pb-free, halogen-free/BFR-free, and RoHS-compliant per onsemi's datasheet revision 3 (June 2024). It meets EU Directive 2011/65/EU and associated amendments. The TO-92-3 Case 135AN package uses lead-free solderable terminations and complies with JEDEC J-STD-020 moisture sensitivity level (MSL) requirements for through-hole reflow and wave soldering.

How does BC556BU differ from BC556BTA?

BC556BU and BC556BTA share identical electrical specifications and TO-92-3 packaging, but differ in lead configuration and packaging format: BC556BU uses straight leads in bulk box (10,000 units), while BC556BTA uses bent leads in fan-fold tape (2,000 units). Both are Class B (h_FE = 200–450) and RoHS-compliant. The choice depends solely on assembly method-not performance or reliability.

What is the typical noise figure of BC556BU and where is it specified?

The BC556BU exhibits a noise figure (NF) of 2–10 dB at 1 kHz, V_CE = −5 V, I_C = −200 µA, and R_G = 2 kΩ, as documented in the "Electrical Characteristics" table on page 2 of the onsemi datasheet. This value positions BC556BU for low-noise small-signal amplification, particularly in microphone preamp and sensor interface circuits where input-referred noise must remain below 10 nV/√Hz.

Can BC556BU replace BC557B in an existing design?

No-BC556BU is not a direct replacement for BC557B due to differing V_CEO ratings: BC556BU supports −65 V while BC557B is rated for −45 V. Substituting BC556BU into a BC557B-design may be safe if voltage stress remains within −45 V, but substituting BC557B into a BC556BU-design risks breakdown. Always validate maximum applied V_CE and transient margins before interchange, and confirm h_FE binning matches system bias requirements for BC556BU.

BC556BU 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:: PNP

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

Voltage - Collector Emitter Breakdown (Max):: 65 V

Vce Saturation (Max) @ Ib, Ic:: 650mV @ 5mA, 100mA

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

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

Power - Max:: 500 mW

Frequency - Transition:: 150MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

BC556BU FAQ

1.How can I place an order for BC556BU through Aetrix?

Please submit a Request for Quotation (RFQ) for BC556BU 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 BC556BU reliable?

The price and inventory of BC556BU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC556BU is usually 5 days.

3.What payment methods are accepted for BC556BU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC556BU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC556BU?

BC556BU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC556BU 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 BC556BU?

For technical support, including BC556BU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC556BU requirements.

6.How does Aetrix verify that BC556BU is sourced from the original manufacturer or authorized distributors?

All BC556BU 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 BC556BU meets industry standards.

7.What is the process for return or replacement of BC556BU?

All BC556BU units undergo pre-shipment inspection (PSI). If there is an issue with BC556BU, 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 BC556BU part is unused and in its original packaging.

Return procedure for BC556BU:

1.Submit a request within 90 days.

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

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