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

onsemi BC550B

Name: BC550B
Brand: onsemi
SKU: BC550B
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC550B

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC550B.pdf

Description:: TRANS NPN 45V 0.1A TO-92-3

Quantity:: RFQ Add To RFQ list

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Inventory:2,341

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Product details

Overview

BC550B from ON Semiconductor is a low-noise NPN epitaxial silicon transistor optimized for small-signal amplification in audio and RF front-end stages, with V_CEO = 45 V, h_FE = 200–450 (Class B), and noise figure of 1.4–3.0 dB at 1 kHz. It operates reliably up to 150°C junction temperature and delivers f_T = 300 MHz at I_C = 10 mA.

For engineers reviewing the BC550B datasheet, pinout, applications, or equivalent options, this page provides verified package mapping (TO-92), terminal roles (C/B/E), low-noise performance data, h_FE classification boundaries, and direct alternatives with documented h_FE and noise differences.

Technical Context

The BC550B is part of the BC546–BC550 family designed as general-purpose, low-noise NPN transistors with standardized TO-92 packaging and JEDEC-compliant pinout (1: Collector, 2: Base, 3: Emitter). Its h_FE range (200–450) and 1.4–3.0 dB noise figure distinguish it from BC549B (1.4–4.0 dB) and BC550C (1.4–3.0 dB, h_FE 420–800).

It shares absolute maximum ratings with the family-V_CBO = 50 V, I_C = 100 mA, P_C = 500 mW-but differs in V_CEO (45 V vs. 65 V for BC546) and V_EBO (5 V), making it unsuitable for high-voltage switching but ideal for precision analog gain stages where noise and gain consistency matter.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	45 V - Maximum collector-emitter voltage before breakdown; sets safe operating range for low-voltage amplifier rails.
h_FE (I_C = 2 mA)	200–450 - DC current gain range defining bias stability and small-signal amplification capability.
Noise Figure	1.4–3.0 dB @ 1 kHz - Confirmed low-noise performance critical for microphone preamps and IF amplifiers.
f_T	300 MHz - Unity-gain bandwidth enabling stable operation up to VHF frequencies in tuned circuits.
V_CE(sat)	90–250 mV @ I_C = 10 mA - Low saturation voltage ensures minimal voltage drop in active-load or switch-mode biasing.
P_C	500 mW - Power dissipation limit requiring heatsinking only above ~250 mW continuous operation.

Pinout & Package

BC550B uses the industry-standard TO-92 3-lead plastic package (JEDEC TO-92 compliant), with straight leads for bulk or ammo packing. Dimensions conform to Fairchild/ON Semiconductor mechanical drawings Rev. 1.1.1.

Pin/Terminal	Circuit Role	Design Meaning
1	Collector	Main current output terminal; connects to load or next stage; requires proper voltage headroom per V_CEO rating.
2	Base	Control input; bias current here determines I_C via h_FE; sensitive to noise coupling due to low-noise design intent.
3	Emitter	Current return path; often grounded or tied to emitter degeneration resistor for stability and linearity.

Key Features

Feature	Design Value
Low-noise amplification	1.4–3.0 dB NF enables use in microphone preamplifiers without audible hiss degradation.
Class B h_FE binning	200–450 gain range allows predictable bias point selection in discrete amplifier designs.
300 MHz f_T	Supports stable small-signal gain up to 30–50 MHz with proper layout and decoupling.
TO-92 compatibility	Direct replacement for legacy BC547/BC548 variants in existing through-hole PCB footprints.

Applications

Audio Preamplifier Stage	RF Signal Amplifier
Use Scenario: Boosting weak signals from electret microphones or piezoelectric sensors before ADC sampling. IC Role / Device Role / Timing Role: Small-signal NPN amplifier configured in common-emitter topology with emitter degeneration. Use Value: 1.4–3.0 dB noise figure preserves signal-to-noise ratio; 200–450 h_FE enables stable DC bias with standard resistor networks.	Use Scenario: Intermediate-frequency (IF) amplification in AM/FM radio receivers operating at 455 kHz or 10.7 MHz. IC Role / Device Role / Timing Role: Linear voltage amplifier in tuned LC-coupled stage with fixed collector load. Use Value: 300 MHz f_T ensures flat gain response across IF bandwidth; low C_ob (3.5–6.0 pF) minimizes tuning capacitor interaction.
Instrumentation Sensor Interface	Low-Power Analog Front-End
Use Scenario: Amplifying millivolt-level outputs from thermocouples or strain gauges in portable test equipment. IC Role / Device Role / Timing Role: First-stage gain element in differential or single-ended configuration with precision biasing. Use Value: 45 V V_CEO accommodates supply rails up to ±20 V; low V_BE(on) (580–700 mV) simplifies low-voltage bias design.	Use Scenario: Signal conditioning in battery-powered IoT sensor nodes requiring long-term stability and low quiescent current. IC Role / Device Role / Timing Role: Active load or gain block in rail-to-rail input amplifier stages powered from 3.3 V or 5 V. Use Value: 500 mW power rating allows thermal margin at <10 mW dissipation; TO-92 footprint supports manual rework and prototyping.

Audio Preamplifier Stage

RF Signal Amplifier

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

IC Role / Device Role / Timing Role: Small-signal NPN amplifier configured in common-emitter topology with emitter degeneration.

Use Value: 1.4–3.0 dB noise figure preserves signal-to-noise ratio; 200–450 h_FE enables stable DC bias with standard resistor networks.

Use Scenario: Intermediate-frequency (IF) amplification in AM/FM radio receivers operating at 455 kHz or 10.7 MHz.

IC Role / Device Role / Timing Role: Linear voltage amplifier in tuned LC-coupled stage with fixed collector load.

Use Value: 300 MHz f_T ensures flat gain response across IF bandwidth; low C_ob (3.5–6.0 pF) minimizes tuning capacitor interaction.

Instrumentation Sensor Interface

Low-Power Analog Front-End

Use Scenario: Amplifying millivolt-level outputs from thermocouples or strain gauges in portable test equipment.

IC Role / Device Role / Timing Role: First-stage gain element in differential or single-ended configuration with precision biasing.

Use Value: 45 V V_CEO accommodates supply rails up to ±20 V; low V_BE(on) (580–700 mV) simplifies low-voltage bias design.

Use Scenario: Signal conditioning in battery-powered IoT sensor nodes requiring long-term stability and low quiescent current.

IC Role / Device Role / Timing Role: Active load or gain block in rail-to-rail input amplifier stages powered from 3.3 V or 5 V.

Use Value: 500 mW power rating allows thermal margin at <10 mW dissipation; TO-92 footprint supports manual rework and prototyping.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN small-signal amplifier applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC549B	Same V_CEO (45 V), identical noise figure (1.4–4.0 dB), but h_FE = 200–450 overlaps BC550B; slightly higher max NF.	Valid in same low-noise audio stages but may require minor bias adjustment due to h_FE distribution variance.	Select BC549B when sourcing legacy stock or when tighter h_FE tolerance is not required.
2N5088	Higher V_CEO (30 V), lower noise (0.8–2.0 dB), h_FE = 300–600; TO-92 compatible but not pin-identical (pinout differs: E-B-C vs. C-B-E).	Superior noise performance suits ultra-low-noise preamps, but requires PCB layout revision due to reversed emitter/collector pins.	Choose 2N5088 only if noise is primary constraint and board redesign is acceptable.

Compared with BC549B and 2N5088, BC550B offers the best balance of verified low-noise operation, standardized TO-92 pinout (C-B-E), and production availability across global distributors-making it optimal for new designs requiring no layout change and guaranteed h_FE binning.

Availability

BC550B is available at Aetrix Electronics and suitable for audio preamplifier stages, RF signal amplifiers, instrumentation sensor interfaces, and low-power analog front-ends requiring stable component supply, consistent h_FE binning, and low-noise transistor performance.

Supply support for BC550B 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, and sensing solutions.

The BC550B belongs to the BC546–BC550 family of general-purpose NPN transistors engineered for low-noise small-signal amplification and switching in consumer, industrial, and communications equipment.

FAQ

What is the pinout configuration of the BC550B?

The BC550B uses a standard TO-92 package with pin 1 as Collector, pin 2 as Base, and pin 3 as Emitter (C-B-E). This matches the JEDEC TO-92 straight-lead configuration documented in Fairchild/ON Semiconductor Rev. 1.1.1 datasheet and is consistent across all BC546–BC550 variants. No alternate pinouts are specified for BC550B.

What does the 'B' suffix indicate in BC550B?

The 'B' in BC550B denotes the h_FE gain classification bin: 200–450 at I_C = 2 mA and V_CE = 5 V. This distinguishes it from BC550A (110–220) and BC550C (420–800). The BC550B designation is factory-trimmed and marked on the device body per ordering information in the datasheet.

Is BC550B suitable for RF amplifier applications?

Yes, BC550B is suitable for RF amplifier applications up to ~50 MHz due to its 300 MHz f_T, low C_ob (3.5–6.0 pF), and stable h_FE across frequency. It has been validated in IF amplifier stages at 10.7 MHz and VHF receiver front-ends; layout best practices (ground plane, short leads, proper decoupling) are required to maintain performance.

How does BC550B compare to BC547B in terms of noise performance?

BC550B has a confirmed noise figure of 1.4–3.0 dB at 1 kHz, while BC547B is not specified for low-noise operation-the datasheet lists only BC549/BC550 for low-noise applications. BC547B's typical noise figure exceeds 10 dB, making BC550B the preferred choice when signal integrity in audio or sensor interfaces is critical.

Can BC550B replace BC549B in an existing design?

Yes, BC550B can directly replace BC549B in most designs: both share identical V_CEO (45 V), V_EBO (5 V), package (TO-92), pinout (C-B-E), and overlapping h_FE (200–450) and noise figure (BC549B: 1.4–4.0 dB; BC550B: 1.4–3.0 dB). No circuit or layout changes are needed, and BC550B offers marginally better noise consistency.

BC550B 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):: 45 V

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

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 200 @ 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

BC550B FAQ

1.How can I place an order for BC550B through Aetrix?

Please submit a Request for Quotation (RFQ) for BC550B 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 BC550B reliable?

The price and inventory of BC550B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC550B is usually 5 days.

3.What payment methods are accepted for BC550B?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC550B transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC550B?

BC550B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC550B 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 BC550B?

For technical support, including BC550B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC550B requirements.

6.How does Aetrix verify that BC550B is sourced from the original manufacturer or authorized distributors?

All BC550B 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 BC550B meets industry standards.

7.What is the process for return or replacement of BC550B?

All BC550B units undergo pre-shipment inspection (PSI). If there is an issue with BC550B, 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 BC550B part is unused and in its original packaging.

Return procedure for BC550B:

1.Submit a request within 90 days.

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

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