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

onsemi BC308BBU

Name: BC308BBU
Brand: onsemi
SKU: BC308BBU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC308BBU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC308BBU.pdf

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

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BC308BBU from Fairchild Semiconductor is a PNP epitaxial silicon transistor in TO-92 package, rated for -30 V V_CES, -25 V V_CEO, -100 mA I_C, 500 mW P_C, and 130 MHz f_T, used in low-noise audio preamplifier stages and general-purpose switching circuits.

For engineers reviewing the BC308BBU datasheet, pinout, applications, or equivalent options, key selection factors include its h_FE classification (B: 180–460), V_BE(sat) of -0.7 V at -10 mA/-0.5 mA, Cob of 6 pF, and suitability for linear amplification below 100 kHz or fast-switching up to 10 kHz with controlled saturation.

Technical Context

The BC308BBU operates as a medium-gain, medium-speed PNP bipolar junction transistor optimized for analog amplification and digital switching in discrete amplifier stages and logic interface circuits. Its h_FE range (180–460) and low noise figure (2 dB at 1 kHz) support stable biasing in Class-A small-signal amplifiers.

It features a V_CE(sat) of -0.5 V at I_C = -10 mA/I_B = -0.5 mA and -0.3 V at I_C = -100 mA/I_B = -5 mA, enabling efficient saturation in low-voltage switching applications. The 6 pF Cob and 12 pF Cib values limit high-frequency gain roll-off above 10 MHz.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CES	-30 V - Maximum collector-emitter voltage before breakdown under open-base condition; defines safe operating voltage in switching applications.
h_FE (B-class)	180–460 - DC current gain range at V_CE = -5 V, I_C = -2 mA; ensures predictable bias stability in amplifier designs.
f_T	130 MHz - Current gain-bandwidth product at V_CE = -5 V, I_C = -10 mA; sets upper frequency limit for small-signal amplification.
Cob	6 pF - Output capacitance at V_CB = -10 V; impacts high-frequency response and Miller effect in common-emitter configurations.
V_BE(on)	-0.55 to -0.7 V - Base-emitter turn-on voltage at V_CE = -5 V, I_C = -2 mA; determines required base drive level for conduction.
P_C	500 mW - Maximum power dissipation at T_A = 25°C; limits continuous collector current in ambient-limited thermal environments.

Pinout & Package

BC308BBU is housed in a standard TO-92 plastic package with 3 leads: Collector (lead 1), Base (lead 2), Emitter (lead 3), compliant with JEDEC TO-92 outline dimensions (14.47 mm length, 4.58 mm width, 3.86 mm height).

Pin/Terminal	Circuit Role	Design Meaning
1 (Collector)	Main current sink terminal	Connected to load or supply rail in common-emitter switching; requires voltage rating ≥ \|V_CES\| = 30 V.
2 (Base)	Control input for minority-carrier injection	Drives transistor into active/saturation via current-limited source; typical I_B = I_C/h_FE ≈ 22–56 µA for 10 mA I_C.
3 (Emitter)	Current source reference terminal	Usually tied to higher potential (e.g., V_CC) in PNP circuits; provides return path for I_C + I_B.

Key Features

Feature	Design Value
Low-noise amplification	2 dB noise figure at 1 kHz, enabling use in microphone preamps and sensor signal conditioning without added noise degradation.
Medium-speed switching	130 MHz f_T supports clean edge transitions in 10–50 kHz digital logic interfaces and PWM drivers.
Stable h_FE classification	B-grade (180–460) ensures consistent gain across production lots, reducing need for per-unit bias trimming in production assemblies.
TO-92 mechanical compatibility	Standard footprint enables drop-in replacement for BC307/BC309 and other TO-92 PNP transistors in legacy PCBs.

Applications

Audio Preamp Stage	Level-Shifting Interface
Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors in battery-powered voice recorders. IC Role / Device Role / Timing Role: Small-signal PNP amplifier in common-emitter configuration with emitter degeneration for linearity. Use Value: 2 dB NF and h_FE ≥180 ensure high SNR and stable gain without external feedback compensation.	Use Scenario: Converting 3.3 V logic outputs to interface with 5 V or 12 V TTL/CMOS inputs in mixed-voltage industrial controllers. IC Role / Device Role / Timing Role: Active pull-up switch with inverted logic polarity, driven by microcontroller GPIO. Use Value: V_CE(sat) ≤ -0.5 V at 10 mA enables <100 mV voltage drop, preserving noise margin on high-side logic lines.
Relay Driver Circuit	Current Mirror Reference
Use Scenario: Driving 12 V/40 mA electromagnetic relays from 5 V microcontroller outputs in HVAC control panels. IC Role / Device Role / Timing Role: Saturated PNP switch with base resistor bias network controlling relay coil current. Use Value: -100 mA I_C rating and -0.3 V V_CE(sat) at 100 mA minimize power loss and heat rise during sustained relay activation.	Use Scenario: Building matched current sources in analog front-ends for precision ADC biasing or sensor excitation. IC Role / Device Role / Timing Role: One leg of a discrete PNP current mirror with emitter resistors for thermal tracking. Use Value: Tight h_FE spread (180–460) and low V_BE variation (-0.55 to -0.7 V) improve mirror accuracy within ±5% over temperature.

Audio Preamp Stage

Level-Shifting Interface

Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors in battery-powered voice recorders.

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

Use Value: 2 dB NF and h_FE ≥180 ensure high SNR and stable gain without external feedback compensation.

Use Scenario: Converting 3.3 V logic outputs to interface with 5 V or 12 V TTL/CMOS inputs in mixed-voltage industrial controllers.

IC Role / Device Role / Timing Role: Active pull-up switch with inverted logic polarity, driven by microcontroller GPIO.

Use Value: V_CE(sat) ≤ -0.5 V at 10 mA enables <100 mV voltage drop, preserving noise margin on high-side logic lines.

Relay Driver Circuit

Current Mirror Reference

Use Scenario: Driving 12 V/40 mA electromagnetic relays from 5 V microcontroller outputs in HVAC control panels.

IC Role / Device Role / Timing Role: Saturated PNP switch with base resistor bias network controlling relay coil current.

Use Value: -100 mA I_C rating and -0.3 V V_CE(sat) at 100 mA minimize power loss and heat rise during sustained relay activation.

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

IC Role / Device Role / Timing Role: One leg of a discrete PNP current mirror with emitter resistors for thermal tracking.

Use Value: Tight h_FE spread (180–460) and low V_BE variation (-0.55 to -0.7 V) improve mirror accuracy within ±5% 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
BC327-40	Same TO-92 package; h_FE = 250–630 (higher gain), V_CEO = -45 V (higher voltage rating), P_C = 625 mW.	Better suited for higher-voltage switching (>30 V) or lower-drive amplification where gain >460 is needed.	Select BC327-40 when V_CEO margin or h_FE headroom is critical; verify thermal derating at 625 mW.
PN2907A	TO-92; h_FE = 100–300 (lower max gain), V_CEO = -60 V, V_CE(sat) = -0.55 V (slightly higher saturation voltage).	Preferred in high-reliability industrial systems requiring extended V_CEO margin and MIL-PRF-19500 qualification.	Choose PN2907A for aerospace/industrial designs needing qualified parts and wider voltage safety margin.

Compared with BC308BBU, BC327-40 offers higher gain and voltage tolerance but requires updated bias calculations, while PN2907A trades some gain for broader qualification and higher V_CEO, making it more suitable for mission-critical overvoltage resilience.

Availability

BC308BBU is available at Aetrix Electronics and suitable for audio preamplifier stages, relay driver circuits, level-shifting interfaces, and current mirror references requiring stable component supply and long-term obsolescence management.

Supply support for BC308BBU 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 BC308BBU belongs to Fairchild's legacy BC307/308/309 PNP transistor family, designed for cost-sensitive, general-purpose linear amplification and switching in consumer, industrial, and automotive auxiliary circuits.

FAQ

What is the maximum collector-emitter voltage rating for BC308BBU?

The BC308BBU has a maximum collector-emitter voltage rating of -30 V under open-base conditions (V_CES) and -25 V with base open (V_CEO). These ratings define absolute limits for safe operation in switching applications; exceeding either value risks avalanche breakdown. Designers must ensure circuit voltages remain within these bounds, especially during transient events or inductive load switching.

What does the 'BBU' suffix indicate in BC308BBU?

The 'BBU' suffix in BC308BBU denotes Fairchild's internal packaging and testing variant: 'B' indicates h_FE classification B (180–460), second 'B' specifies TO-92 package with lead finish per J-STD-020, and 'U' signifies tape-and-reel packaging per EIA-481. This coding confirms the part meets standard reliability screening and is not a special-order or untested lot.

Can BC308BBU replace BC307 or BC309 in existing designs?

BC308BBU can replace BC307 in most circuits due to identical pinout and similar gain/noise specs, but not BC309 in low-noise-critical applications: BC309 has 4 dB NF at 30–15 kHz vs. BC308BBU's 2 dB at 1 kHz only. Also, BC308BBU's lower V_CEO (-25 V) versus BC307 (-45 V) requires voltage margin review before substitution.

What is the typical base-emitter on voltage for BC308BBU?

The typical base-emitter on voltage (V_BE(on)) for BC308BBU is -0.62 V at V_CE = -5 V and I_C = -2 mA, with a guaranteed range of -0.55 V to -0.7 V. This value determines the minimum base drive voltage needed to achieve target collector current and directly affects bias network resistor sizing in amplifier or switch designs.

Is BC308BBU suitable for high-frequency RF amplification?

No, BC308BBU is not suitable for RF amplification above ~10 MHz. Although its f_T is 130 MHz, its Cob (6 pF) and Cib (12 pF) cause significant gain roll-off and phase shift in common-emitter configurations above 10 MHz. It is optimized for audio and low-speed switching-not RF, VHF, or broadband applications-where parasitic capacitance degrades performance.

BC308BBU 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):: 25 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 5mA, 100mA

Current - Collector Cutoff (Max):: 15nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 180 @ 2mA, 5V

Power - Max:: 500 mW

Frequency - Transition:: 130MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

BC308BBU FAQ

1.How can I place an order for BC308BBU through Aetrix?

Please submit a Request for Quotation (RFQ) for BC308BBU 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 BC308BBU reliable?

The price and inventory of BC308BBU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC308BBU is usually 5 days.

3.What payment methods are accepted for BC308BBU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC308BBU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC308BBU?

BC308BBU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC308BBU 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 BC308BBU?

For technical support, including BC308BBU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC308BBU requirements.

6.How does Aetrix verify that BC308BBU is sourced from the original manufacturer or authorized distributors?

All BC308BBU 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 BC308BBU meets industry standards.

7.What is the process for return or replacement of BC308BBU?

All BC308BBU units undergo pre-shipment inspection (PSI). If there is an issue with BC308BBU, 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 BC308BBU part is unused and in its original packaging.

Return procedure for BC308BBU:

1.Submit a request within 90 days.

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

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