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

onsemi BC558

Name: BC558
Brand: onsemi
SKU: BC558
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC558

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC558.pdf

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

Quantity:: RFQ Add To RFQ list

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Inventory:8,512

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Product details

Overview

BC558 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 = −30 V, I_C = −100 mA, h_FE = 110–800 (Class B), V_CE(sat) = −90 to −650 mV, and f_T = 150 MHz - enabling use in audio preamplifiers, level shifters, and discrete logic interfaces.

For engineers reviewing the BC558 datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-92-3 (case 135AR) package, complementary pairing with BC548, low-noise capability among BC556–BC558 variants, and RoHS-compliant Pb-free construction.

Technical Context

The BC558 operates as a medium-gain, medium-voltage PNP bipolar junction transistor optimized for DC-coupled amplification and saturated switching. Its h_FE classification (B: 200–450) ensures predictable current gain at I_C = −2 mA and V_CE = −5 V, while V_CE(sat) remains below −300 mV at I_C = −10 mA / I_B = −0.5 mA - supporting efficient low-side switch operation.

Thermal performance is defined by R_JA = 250 °C/W (FR-4 PCB, 76 mm × 114 mm), with PD = 500 mW at T_A = 25 °C and 4.0 mW/°C derating above. Its Cob = 6 pF at V_CB = −10 V enables stable high-frequency biasing up to 150 MHz f_T.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−30 V - Maximum collector-emitter voltage before breakdown; sets safe operating range for low-voltage PNP switching stages.
I_C (DC)	−100 mA - Continuous collector current limit; supports signal-level loads like LED drivers or small relays.
h_FE (Class B)	200–450 - Confirmed DC current gain range at V_CE = −5 V, I_C = −2 mA; enables predictable base drive calculation.
V_CE(sat)	−90 to −650 mV - Saturation voltage across collector-emitter under specified drive; determines power loss in switching mode.
f_T	150 MHz - Current gain bandwidth product at V_CE = −5 V, I_C = −10 mA; validates suitability for RF biasing and wideband amplification.
C_ob	6 pF - Output capacitance at V_CB = −10 V; limits high-frequency instability in amplifier feedback networks.
NF	2–10 dB - Noise figure at V_CE = −5 V, I_C = −200 µA, f = 1 kHz; confirms low-noise performance for audio front-end stages.

Pinout & Package

BC558 is housed in a TO-92-3 plastic package (case 135AR), lead-formed, with standard through-hole mounting. Dimensions: 4.83 mm × 4.76 mm × 4.0 mm.

Pin/Terminal	Circuit Role	Design Meaning
1	Collector	Primary current sink terminal; connects to load or supply rail in PNP common-emitter configurations.
2	Base	Control input; requires negative current relative to emitter to turn on; drives switching or bias networks.
3	Emitter	Current source terminal; typically tied to positive supply in PNP applications; reference point for base-emitter voltage.

Key Features

Feature	Design Value
Complementary Pairing	Matched as PNP counterpart to BC548 NPN - enables balanced push-pull output stages and differential amplifiers.
Low-Noise Amplification	2–10 dB noise figure (1 kHz) - validated for microphone preamps and sensor signal conditioning where SNR matters.
Pb-Free & RoHS Compliance	Halogen-free/BFR-free construction - meets global environmental regulations without compromising thermal or electrical performance.
High h_FE Consistency	Class B (200–450) gain binning - reduces need for individual gain trimming in production assemblies.

Applications

Audio Preamp Stage	Discrete Logic Level Shifter
Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors in portable audio devices. IC Role / Device Role / Timing Role: Small-signal PNP amplifier in common-emitter configuration with emitter degeneration for linearity. Use Value: 2–10 dB noise figure and 150 MHz f_T preserve signal integrity while enabling compact, low-cost front-end design.	Use Scenario: Translating 3.3 V logic outputs to −5 V or −12 V control rails in legacy industrial interface modules. IC Role / Device Role / Timing Role: Inverting level translator using saturated PNP switching with fixed base resistor network. Use Value: V_CE(sat) ≤ −300 mV at I_C = −10 mA ensures minimal voltage drop and fast edge transitions.
LED Driver (Low-Side)	Current Mirror Reference
Use Scenario: Driving indicator LEDs or optocoupler inputs from microcontroller GPIO pins with inverted logic polarity. IC Role / Device Role / Timing Role: Saturated PNP switch with emitter connected to V_CC, collector driving LED cathode to ground. Use Value: −100 mA I_C rating and −90 mV min V_CE(sat) allow direct drive of multiple LEDs with <100 mW dissipation.	Use Scenario: Establishing matched reference currents in analog ICs or precision sensor biasing circuits. IC Role / Device Role / Timing Role: Active component in two-transistor current mirror topology with matched h_FE and thermal tracking. Use Value: Tight h_FE binning (Class B) and low V_BE(on) variation (−600 to −750 mV) improve mirror accuracy over temperature.

Audio Preamp Stage

Discrete Logic Level Shifter

Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors in portable audio devices.

IC Role / Device Role / Timing Role: Small-signal PNP amplifier in common-emitter configuration with emitter degeneration for linearity.

Use Value: 2–10 dB noise figure and 150 MHz f_T preserve signal integrity while enabling compact, low-cost front-end design.

Use Scenario: Translating 3.3 V logic outputs to −5 V or −12 V control rails in legacy industrial interface modules.

IC Role / Device Role / Timing Role: Inverting level translator using saturated PNP switching with fixed base resistor network.

Use Value: V_CE(sat) ≤ −300 mV at I_C = −10 mA ensures minimal voltage drop and fast edge transitions.

LED Driver (Low-Side)

Current Mirror Reference

Use Scenario: Driving indicator LEDs or optocoupler inputs from microcontroller GPIO pins with inverted logic polarity.

IC Role / Device Role / Timing Role: Saturated PNP switch with emitter connected to V_CC, collector driving LED cathode to ground.

Use Value: −100 mA I_C rating and −90 mV min V_CE(sat) allow direct drive of multiple LEDs with <100 mW dissipation.

Use Scenario: Establishing matched reference currents in analog ICs or precision sensor biasing circuits.

IC Role / Device Role / Timing Role: Active component in two-transistor current mirror topology with matched h_FE and thermal tracking.

Use Value: Tight h_FE binning (Class B) and low V_BE(on) variation (−600 to −750 mV) improve mirror accuracy over temperature.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC557BTA	V_CEO = −45 V, V_CBO = −50 V - higher voltage rating than BC558's −30 V.	Preferred in 24 V industrial control where higher breakdown margin is required.	Select BC557BTA when V_CE stress exceeds −30 V; otherwise BC558 offers tighter h_FE consistency at lower cost.
BC559BTA	Lower noise figure (1–4 dB vs. 2–10 dB) and same V_CEO = −30 V - optimized for ultra-low-noise audio.	Used in high-fidelity microphone preamps where sub-2 dB NF is mandatory.	Choose BC559BTA only if measured noise performance is critical; BC558 provides better cost/performance balance for general audio.

Compared with BC557BTA and BC559BTA, BC558 delivers optimal trade-off between voltage rating, noise, gain consistency, and cost for mainstream low-power PNP applications - making it the default choice unless specific higher-voltage or ultra-low-noise requirements apply.

Availability

BC558 is available at Aetrix Electronics and suitable for audio preamplifiers, discrete logic level shifters, and LED driver circuits requiring stable component supply, long-term obsolescence management, and RoHS-compliant sourcing.

Supply support for BC558 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, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC558 belongs to onsemi's legacy general-purpose bipolar transistor family, engineered for reliability, manufacturability, and compatibility with standard PCB assembly processes in cost-sensitive analog and mixed-signal designs.

FAQ

What is the maximum collector-emitter voltage rating for BC558?

The BC558 has a maximum collector-emitter voltage (V_CEO) rating of −30 V at T_A = 25 °C. This value is confirmed in the Absolute Maximum Ratings table of the official onsemi datasheet (Rev. 3, June 2024). Exceeding this voltage risks avalanche breakdown and permanent device failure. Derating is not specified beyond ambient temperature limits, so design margins should maintain at least 20% headroom in static applications.

Is BC558 pin-compatible with BC548?

Yes, BC558 is the complementary PNP counterpart to the NPN BC548, sharing identical TO-92-3 (case 135AR) package and pinout: Collector (pin 1), Base (pin 2), Emitter (pin 3). This allows direct substitution in push-pull, differential pair, and level-shifting circuits - provided polarity and biasing are reversed. The BC558 datasheet explicitly states "Complement to BC546, BC547, BC548, BC549, and BC550".

What h_FE range does BC558BTA guarantee?

The BC558BTA guarantees an h_FE (DC current gain) range of 200 to 450 at V_CE = −5 V and I_C = −2 mA, per the h_FE Classification table in the onsemi datasheet. This Class B binning is verified during production test and applies specifically to the "B" suffix variant. Units marked "BC558B" on the package confirm this gain range.

Does BC558 support high-frequency amplification?

Yes, BC558 supports high-frequency amplification with a current gain bandwidth product (f_T) of 150 MHz under standard conditions (V_CE = −5 V, I_C = −10 mA, f = 10 MHz). This is confirmed in the Electrical Characteristics table. While not intended for RF power stages, it is suitable for wideband audio, IF amplification, and clock buffer applications where gain stability up to ~50 MHz is required.

What is the thermal resistance of BC558 in typical PCB layout?

The BC558 has a junction-to-ambient thermal resistance (R_JA) of 250 °C/W when mounted on a standard FR-4 PCB measuring 76 mm × 114 mm × 1.57 mm with minimum land pattern. This value is specified in the Thermal Characteristics section of the onsemi datasheet and assumes natural convection cooling. Derating begins at 4.0 mW/°C above 25 °C ambient, limiting usable power dissipation to ~300 mW at 100 °C case temperature.

BC558 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:: 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

BC558 FAQ

1.How can I place an order for BC558 through Aetrix?

Please submit a Request for Quotation (RFQ) for BC558 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 BC558 reliable?

The price and inventory of BC558 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC558 is usually 5 days.

3.What payment methods are accepted for BC558?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC558 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC558?

BC558 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC558 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 BC558?

For technical support, including BC558 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC558 requirements.

6.How does Aetrix verify that BC558 is sourced from the original manufacturer or authorized distributors?

All BC558 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 BC558 meets industry standards.

7.What is the process for return or replacement of BC558?

All BC558 units undergo pre-shipment inspection (PSI). If there is an issue with BC558, 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 BC558 part is unused and in its original packaging.

Return procedure for BC558:

1.Submit a request within 90 days.

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

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