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

onsemi BC558CBU

Name: BC558CBU
Brand: onsemi
SKU: BC558CBU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC558CBU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC558CBU.pdf

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

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BC558CBU from onsemi is a PNP epitaxial silicon transistor designed for general-purpose switching and linear amplification in low-to-medium power circuits. It features V_CEO = −30 V, I_C = −100 mA, h_FE = 420–800 (Class C), V_CE(sat) ≤ −650 mV at I_C = −100 mA/I_B = −5 mA, and f_T = 150 MHz - enabling use in audio preamplifiers, relay drivers, and level-shifting interfaces.

For engineers reviewing the BC558CBU datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-92-3 (Case 135AR) package, complementary pairing with BC548/BC549 NPN devices, low-noise capability (NF = 1–4 dB at 1 kHz), and RoHS-compliant Pb-free construction.

Technical Context

The BC558CBU operates as a medium-gain, medium-voltage PNP bipolar junction transistor optimized for DC-coupled amplification and saturated-switching operation. Its h_FE classification (C: 420–800) ensures consistent current gain across production lots, while V_CEO = −30 V and V_CBO = −30 V define safe operating limits in negative-rail bias configurations.

Thermal performance is characterized by R_JA = 250 °C/W (FR-4 PCB, 76 mm × 114 mm), PD = 500 mW at 25°C with 4.0 mW/°C derating - supporting stable operation in ambient temperatures up to +125°C when mounted per standard land patterns. Noise figure (NF = 1–4 dB) confirms suitability for low-noise analog stages where signal integrity is critical.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−30 V - Maximum collector-emitter voltage before breakdown; defines rail compatibility in −24 V or −15 V systems.
I_C (DC)	−100 mA - Continuous collector current limit; supports driving LEDs, small relays, or logic-level shifters.
h_FE (Class C)	420–800 - High DC current gain enables low-base-drive designs, reducing MCU GPIO loading in discrete amplifier stages.
V_CE(sat)	≤ −650 mV @ I_C = −100 mA/I_B = −5 mA - Low saturation voltage minimizes power loss in switching applications.
f_T	150 MHz - Unity-gain bandwidth allows stable operation up to audio and low-RF frequencies without oscillation.
NF	1–4 dB @ 1 kHz - Confirmed low-noise performance for microphone preamps and sensor signal conditioning.

Pinout & Package

BC558CBU is housed in a TO-92-3 plastic package (Case 135AR), lead-formed, with standardized pin assignment verified per onsemi mechanical drawings 98AON13879G.

Pin/Terminal	Circuit Role	Design Meaning
1 (Top view, flat side facing user)	Collector	Main current sink terminal; connects to negative supply rail or load return path in PNP configurations.
2	Base	Control input; requires negative bias relative to emitter to turn on; typically driven via resistor from MCU or op-amp output.
3	Emitter	Current source terminal; tied to most-positive system node (e.g., V_CC) in common-emitter switching setups.

Key Features

Feature	Design Value
Complementary Pairing	Designed as direct PNP counterpart to BC548/BC549 NPN transistors - simplifies push-pull stage design with matched thermal and gain characteristics.
Low-Noise Operation	NF = 1–4 dB at 1 kHz enables use in sensitive analog front-ends without requiring additional noise-filtering components.
Pb-Free & RoHS Compliance	Fully compliant with EU RoHS Directive 2011/65/EU and halogen-free/BFR-free requirements - supports green manufacturing and export compliance.
High h_FE Consistency	Class C h_FE range (420–800) reduces binning overhead and improves predictability in production-grade amplifier gain staging.

Applications

Audio Preamp Stage	Relay Driver Circuit
Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors before ADC sampling. IC Role / Device Role / Timing Role: Discrete PNP transistor configured in common-emitter topology for voltage gain and impedance matching. Use Value: Low NF (1–4 dB) preserves signal-to-noise ratio; high h_FE allows single-stage gain >100 with minimal base drive current.	Use Scenario: Driving 5–12 V coil relays from microcontroller GPIO pins with open-collector or active-low logic. IC Role / Device Role / Timing Role: Saturated switch controlling relay coil current path to ground (emitter-connected to V_CC, collector to coil). Use Value: V_CE(sat) ≤ −650 mV ensures <10 mW dissipation at 100 mA, eliminating need for heatsinking in compact PCB layouts.
Level-Shifting Interface	Discrete Logic Inverter
Use Scenario: Converting 3.3 V logic outputs to −5 V or −12 V control signals for legacy industrial equipment. IC Role / Device Role / Timing Role: PNP-based inverting level shifter with emitter tied to negative rail, collector pulled up to target voltage. Use Value: V_CBO = −30 V and V_CEO = −30 V support reliable operation across extended negative voltage ranges without breakdown.	Use Scenario: Implementing non-inverting or inverting logic functions in repair scenarios or prototyping where ICs are unavailable. IC Role / Device Role / Timing Role: Discrete BJT used as digital inverter with fixed bias network and pull-up resistor. Use Value: Fast f_T = 150 MHz enables clean transitions up to ~10 MHz clock rates; TO-92 footprint allows hand-soldering and field replacement.

Audio Preamp Stage

Relay Driver Circuit

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

IC Role / Device Role / Timing Role: Discrete PNP transistor configured in common-emitter topology for voltage gain and impedance matching.

Use Value: Low NF (1–4 dB) preserves signal-to-noise ratio; high h_FE allows single-stage gain >100 with minimal base drive current.

Use Scenario: Driving 5–12 V coil relays from microcontroller GPIO pins with open-collector or active-low logic.

IC Role / Device Role / Timing Role: Saturated switch controlling relay coil current path to ground (emitter-connected to V_CC, collector to coil).

Use Value: V_CE(sat) ≤ −650 mV ensures <10 mW dissipation at 100 mA, eliminating need for heatsinking in compact PCB layouts.

Level-Shifting Interface

Discrete Logic Inverter

Use Scenario: Converting 3.3 V logic outputs to −5 V or −12 V control signals for legacy industrial equipment.

IC Role / Device Role / Timing Role: PNP-based inverting level shifter with emitter tied to negative rail, collector pulled up to target voltage.

Use Value: V_CBO = −30 V and V_CEO = −30 V support reliable operation across extended negative voltage ranges without breakdown.

Use Scenario: Implementing non-inverting or inverting logic functions in repair scenarios or prototyping where ICs are unavailable.

IC Role / Device Role / Timing Role: Discrete BJT used as digital inverter with fixed bias network and pull-up resistor.

Use Value: Fast f_T = 150 MHz enables clean transitions up to ~10 MHz clock rates; TO-92 footprint allows hand-soldering and field replacement.

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
BC558BTA	Same TO-92-3 (135AR) package; h_FE = 200–450 (Class B); identical V_CEO/I_C/f_T specs.	Slightly lower gain reduces base drive sensitivity but improves stability in high-temperature environments.	Select BC558BTA when tighter h_FE tolerance and reduced gain variation over temperature are prioritized.
BC557BTA	V_CEO = −45 V, V_CBO = −50 V; same h_FE Class B range; otherwise identical pinout and package.	Higher voltage rating supports use in −36 V or −48 V telecom subsystems where BC558CBU would be out-of-spec.	Choose BC557BTA for applications requiring >−30 V collector-emitter blocking capability without changing layout.

Compared with BC558BTA and BC557BTA, the BC558CBU offers highest DC gain (420–800) for low-base-current designs, while sacrificing some voltage headroom versus BC557BTA and gain consistency versus BC558BTA - making it optimal for noise-sensitive, gain-critical analog stages within its −30 V operational envelope.

Availability

BC558CBU is available at Aetrix Electronics and suitable for audio preamplifiers, relay driver circuits, and level-shifting interfaces requiring stable component supply, long-term obsolescence management, and full traceability.

Supply support for BC558CBU 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 BC558CBU belongs to onsemi's legacy BC5xx PNP/NPN transistor family, engineered for cost-effective, robust discrete signal conditioning and switching in consumer, industrial, and communications equipment.

FAQ

What is the maximum continuous collector current rating for BC558CBU?

The BC558CBU has a maximum continuous collector current (I_C) of −100 mA at T_A = 25°C. This rating assumes proper PCB thermal management per the FR-4 reference layout (76 mm × 114 mm). Derating applies above 25°C at 4.0 mW/°C, limiting usable current in high-ambient environments. Exceeding −100 mA risks thermal runaway or permanent degradation of the BC558CBU device.

Is BC558CBU pin-compatible with BC558BTA or BC558ATA?

Yes - BC558CBU shares identical TO-92-3 (Case 135AR) packaging and pinout (Collector-Base-Emitter, left-to-right with flat side facing) with BC558BTA and BC558ATA. All three variants use the same mechanical outline and land pattern, allowing direct substitution on PCBs without layout changes. The only functional difference lies in h_FE classification: BC558CBU (Class C: 420–800), BC558BTA (Class B: 200–450), BC558ATA (Class A: 110–220).

Does BC558CBU support low-noise audio applications?

Yes - the BC558CBU is specified with a noise figure (NF) of 1–4 dB at 1 kHz (V_CE = −5 V, I_C = −200 µA, R_G = 2 kΩ), confirming its suitability for low-noise audio preamplifier stages. This performance is validated in the official onsemi datasheet and distinguishes it from standard-switching variants like BC556. For best results, operate the BC558CBU within its recommended I_C range (0.1–10 mA) and use proper shielding and grounding practices.

What is the junction-to-ambient thermal resistance (R_JA) of BC558CBU?

The BC558CBU has a junction-to-ambient thermal resistance (R_JA) of 250 °C/W under standard test conditions: FR-4 PCB, 76 mm × 114 mm × 1.57 mm, with minimum land pattern size. This value assumes natural convection cooling and no forced airflow. At full 500 mW power dissipation, this yields a theoretical junction temperature rise of 125°C above ambient - meaning operation above +25°C ambient requires careful thermal design to stay within the 150°C maximum junction temperature limit of the BC558CBU.

Can BC558CBU replace BC557BTA in a circuit?

BC558CBU can replace BC557BTA only if the circuit operates within −30 V collector-emitter voltage - because BC557BTA supports V_CEO = −45 V while BC558CBU is rated for −30 V. Gain and switching behavior are otherwise compatible (same package, pinout, f_T, and saturation characteristics). However, substituting BC558CBU into a −40 V rail application risks premature breakdown. Always verify voltage margins before interchanging BC558CBU and BC557BTA in existing designs.

BC558CBU 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):: 30 V

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

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 420 @ 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

BC558CBU FAQ

1.How can I place an order for BC558CBU through Aetrix?

Please submit a Request for Quotation (RFQ) for BC558CBU 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 BC558CBU reliable?

The price and inventory of BC558CBU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC558CBU is usually 5 days.

3.What payment methods are accepted for BC558CBU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC558CBU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC558CBU?

BC558CBU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC558CBU 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 BC558CBU?

For technical support, including BC558CBU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC558CBU requirements.

6.How does Aetrix verify that BC558CBU is sourced from the original manufacturer or authorized distributors?

All BC558CBU 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 BC558CBU meets industry standards.

7.What is the process for return or replacement of BC558CBU?

All BC558CBU units undergo pre-shipment inspection (PSI). If there is an issue with BC558CBU, 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 BC558CBU part is unused and in its original packaging.

Return procedure for BC558CBU:

1.Submit a request within 90 days.

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

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