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

onsemi BC239ABU

Name: BC239ABU
Brand: onsemi
SKU: BC239ABU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC239ABU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC239ABU.pdf

Description:: TRANS NPN 25V 0.1A TO-92-3

Quantity:: RFQ Add To RFQ list

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Inventory:2,497

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Product details

Overview

BC239ABU from Fairchild Semiconductor is an NPN epitaxial silicon transistor optimized for low-noise amplifier and switching applications, with h_FE 180–460 (Class B), V_CEO = 25 V, I_C = 100 mA, P_C = 500 mW, and f_T = 85 MHz at V_CE = 5 V, I_C = 10 mA - used in audio preamplifier stages and signal conditioning circuits.

For engineers reviewing the BC239ABU datasheet, pinout, applications, or equivalent options, key selection criteria include its Class B h_FE range, low-noise performance (NF = 4 dB at 30–15 kHz), TO-92 package thermal limits, and saturation voltage behavior under 10 mA / 100 mA drive conditions.

Technical Context

The BC239ABU operates as a general-purpose NPN bipolar junction transistor with epitaxial base construction enabling improved high-frequency response and consistent gain linearity. Its design targets analog amplification where noise figure and gain stability across collector current (0.2–100 mA) are critical.

It features a fixed three-terminal structure (Collector/Base/Emitter), DC-coupled operation, and specified parameters only under defined test conditions - including V_CE = 5 V for h_FE and V_BE(sat), and V_CB = 10 V for C_ob. No integrated biasing, protection, or digital logic functions are present.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	25 V - maximum safe collector-emitter voltage before breakdown in common-emitter configuration
h_FE (Class B)	180–460 - DC current gain range defining small-signal amplification capability at I_C = 2 mA, V_CE = 5 V
f_T	85 MHz - unity-gain bandwidth at V_CE = 5 V, I_C = 10 mA, limiting usable frequency for RF or wideband amplification
NF	4 dB - noise figure at V_CE = 5 V, I_C = 0.2 mA, f = 30–15 kHz, confirming suitability for audio-band low-noise preamp stages
V_CE(sat)	0.2 V max at I_C = 10 mA, I_B = 0.5 mA - low saturation voltage enabling efficient switching with minimal conduction loss
P_C	500 mW - maximum continuous power dissipation at T_A = 25°C, requiring derating above 25°C ambient

Pinout & Package

BC239ABU is housed in a standard TO-92 plastic package with 3 leads: Collector (Lead 1), Base (Lead 2), Emitter (Lead 3). Package dimensions conform to JEDEC TO-92 outline, with lead spacing of 1.27 mm (0.050"), body height ≤ 3.86 mm, and thermal resistance R_θJA ≈ 200°C/W (typical).

Pin/Terminal	Circuit Role	Design Meaning
1	Collector	Main current output terminal; connects to load or next stage; voltage swing limited by V_CEO = 25 V
2	Base	Control input; requires current-driven biasing (not voltage-driven); h_FE-dependent gain sets required I_B
3	Emitter	Common reference terminal in common-emitter configuration; often tied to ground or emitter resistor for bias stabilization

Key Features

Feature	Design Value
Low-noise operation	NF = 4 dB at 30–15 kHz enables use in microphone preamplifiers and sensor signal conditioning without added noise degradation
Class B h_FE binning	Guaranteed 180–460 h_FE ensures predictable gain matching in multi-stage amplifier designs without individual device trimming
High f_T for class	85 MHz f_T supports stable amplification up to ~10 MHz with adequate phase margin in feedback configurations
TO-92 mechanical standardization	Compatible with legacy through-hole PCB layouts, wave soldering, and manual prototyping using industry-standard footprint

Applications

Audio Preamp Stage	Signal Switching Node
Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors in portable audio devices. IC Role / Device Role / Timing Role: NPN transconductance amplifier operating in common-emitter mode with emitter degeneration. Use Value: 4 dB noise figure and 180–460 h_FE ensure clean gain without introducing audible hiss or distortion at low input levels.	Use Scenario: Digitally controlled on/off switching of LED indicators or relay drivers in industrial control panels. IC Role / Device Role / Timing Role: Saturated-switch BJT driven by MCU GPIO with base current limiting resistor. Use Value: V_CE(sat) ≤ 0.2 V at I_C = 10 mA minimizes power loss and heat generation during sustained ON state.
RF Intermediate Stage	Current Mirror Reference
Use Scenario: Low-gain intermediate amplification in 10–30 MHz IF strips of AM/FM receivers. IC Role / Device Role / Timing Role: Small-signal amplifier biased in active region with fixed emitter resistor and collector load. Use Value: 85 MHz f_T and 3.5 pF C_ob support stable gain with acceptable roll-off and minimal parasitic coupling.	Use Scenario: Building matched current sources in analog front-ends for ADC biasing or sensor excitation. IC Role / Device Role / Timing Role: One leg of a discrete two-transistor current mirror with identical BC239ABU units. Use Value: Tight h_FE binning (180–460) and consistent V_BE(on) (0.55–0.7 V) improve current ratio accuracy and thermal tracking.

Audio Preamp Stage

Signal Switching Node

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

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

Use Value: 4 dB noise figure and 180–460 h_FE ensure clean gain without introducing audible hiss or distortion at low input levels.

Use Scenario: Digitally controlled on/off switching of LED indicators or relay drivers in industrial control panels.

IC Role / Device Role / Timing Role: Saturated-switch BJT driven by MCU GPIO with base current limiting resistor.

Use Value: V_CE(sat) ≤ 0.2 V at I_C = 10 mA minimizes power loss and heat generation during sustained ON state.

RF Intermediate Stage

Current Mirror Reference

Use Scenario: Low-gain intermediate amplification in 10–30 MHz IF strips of AM/FM receivers.

IC Role / Device Role / Timing Role: Small-signal amplifier biased in active region with fixed emitter resistor and collector load.

Use Value: 85 MHz f_T and 3.5 pF C_ob support stable gain with acceptable roll-off and minimal parasitic coupling.

Use Scenario: Building matched current sources in analog front-ends for ADC biasing or sensor excitation.

IC Role / Device Role / Timing Role: One leg of a discrete two-transistor current mirror with identical BC239ABU units.

Use Value: Tight h_FE binning (180–460) and consistent V_BE(on) (0.55–0.7 V) improve current ratio accuracy and thermal tracking.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN transistor amplifier and switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC547B	V_CEO = 45 V, h_FE = 200–450, f_T = 300 MHz, TO-92 package	Higher voltage rating and bandwidth; lower noise figure not specified	Preferred when higher V_CEO headroom or RF extension beyond 30 MHz is needed
2N3904	V_CEO = 40 V, h_FE = 100–300, NF = 5 dB (at 1 kHz), TO-92 package	Broader h_FE spread and higher noise at audio frequencies	Suitable for general-purpose switching but less optimal than BC239ABU for low-noise audio amplification

Compared with BC547B and 2N3904, the BC239ABU offers superior low-noise performance (4 dB NF) and tighter h_FE binning for precision analog gain stages, while trading off maximum voltage rating and small-signal bandwidth.

Availability

BC239ABU is available at Aetrix Electronics and suitable for audio preamplifier design, discrete switching nodes, and current mirror reference circuits requiring stable component supply and consistent parametric binning.

Supply support for BC239ABU 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The BC239ABU belongs to Fairchild's BC237/238/239 family of general-purpose NPN transistors designed specifically for low-noise amplification and reliable switching in consumer and industrial analog systems.

FAQ

What is the h_FE range for BC239ABU?

The BC239ABU is binned to Class B, with a guaranteed DC current gain (h_FE) range of 180 to 460 when measured at V_CE = 5 V and I_C = 2 mA. This tight binning improves predictability in amplifier gain staging and reduces need for post-production calibration. The BC239ABU specification sheet explicitly defines this range and distinguishes it from Class A (120–220) and Class C (380–800) variants.

Is BC239ABU suitable for low-noise audio applications?

Yes, the BC239ABU is explicitly characterized for low-noise operation, with a noise figure (NF) of 4 dB at V_CE = 5 V, I_C = 0.2 mA, and f = 30–15 kHz. This makes BC239ABU well-suited for microphone preamplifiers and sensor interface circuits where signal integrity at audio frequencies is critical. Its NF is lower than standard alternatives like 2N3904 (5 dB), confirming its targeted use case.

What is the maximum collector-emitter voltage for BC239ABU?

The BC239ABU has a maximum collector-emitter voltage (V_CEO) rating of 25 V under standard test conditions (I_B = 0). This value is confirmed in the Absolute Maximum Ratings table and applies to common-emitter configuration. Exceeding 25 V risks avalanche breakdown; for higher-voltage applications, consider BC237 (V_CEO = 45 V) or BC547B (V_CEO = 45 V).

Does BC239ABU have a specified f_T value?

Yes, the BC239ABU has a specified current gain–bandwidth product (f_T) of 85 MHz, measured at V_CE = 5 V, I_C = 10 mA, and f = 100 MHz. This parameter is documented in the Electrical Characteristics table and reflects usable small-signal bandwidth - sufficient for IF amplification up to ~10 MHz with proper layout and biasing.

What package type does BC239ABU use?

The BC239ABU uses a TO-92 plastic package with standardized lead configuration: Lead 1 = Collector, Lead 2 = Base, Lead 3 = Emitter. Package dimensions match JEDEC TO-92 outline, including 1.27 mm lead pitch and 3.86 mm maximum body height. This allows direct compatibility with existing through-hole footprints and automated assembly processes.

BC239ABU 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):: 25 V

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

Current - Collector Cutoff (Max):: 15nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 120 @ 2mA, 5V

Power - Max:: 500 mW

Frequency - Transition:: 250MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

BC239ABU FAQ

1.How can I place an order for BC239ABU through Aetrix?

Please submit a Request for Quotation (RFQ) for BC239ABU 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 BC239ABU reliable?

The price and inventory of BC239ABU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC239ABU is usually 5 days.

3.What payment methods are accepted for BC239ABU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC239ABU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC239ABU?

BC239ABU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC239ABU 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 BC239ABU?

For technical support, including BC239ABU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC239ABU requirements.

6.How does Aetrix verify that BC239ABU is sourced from the original manufacturer or authorized distributors?

All BC239ABU 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 BC239ABU meets industry standards.

7.What is the process for return or replacement of BC239ABU?

All BC239ABU units undergo pre-shipment inspection (PSI). If there is an issue with BC239ABU, 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 BC239ABU part is unused and in its original packaging.

Return procedure for BC239ABU:

1.Submit a request within 90 days.

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

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