onsemi BC309BBU

Overview

BC309BBU from Fairchild Semiconductor is a PNP epitaxial silicon transistor optimized for low-noise amplifier and switching applications, with V_CEO = −25 V, I_C = −100 mA, P_C = 500 mW, h_FE = 180–460 (Class B), and f_T = 130 MHz - used in audio preamplifier stages and relay drivers.

For engineers reviewing the BC309BBU datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package, low-noise performance (NF = 4 dB at 30–15 kHz), saturation voltage behavior (V_CE(sat) = −0.3 V @ I_C = −100 mA), and h_FE classification band.

Technical Context

This PNP bipolar junction transistor operates in common-emitter configuration with verified DC current gain linearity across I_C = −0.2 mA to −100 mA and stable V_BE(on) = −0.55 to −0.7 V. Its low output capacitance (C_ob = 6 pF) and input capacitance (C_ib = 12 pF) support high-frequency small-signal amplification up to 130 MHz.

The BC309BBU exhibits defined breakdown limits: V_CES = −30 V, V_EBO = −5 V, and guaranteed junction temperature tolerance up to 150°C - enabling reliable operation in thermally constrained analog and discrete logic interface circuits.

Key Specifications

Pinout & Package

BC309BBU is housed in a standard TO-92 plastic package (3.60 × 4.58 × 1.02 mm), lead-free compatible, with epoxy-molded construction rated for T_J = −55°C to +150°C operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC309BBU, BC327-40 offers higher voltage headroom and gain for demanding analog interfaces, while PN2907A trades noise specification for wider availability and ruggedness in digital switching - neither is pin-compatible without verifying layout clearance for alternate h_FE-driven base resistor values.

Availability

BC309BBU is available at Aetrix Electronics and suitable for audio preamplifier stages, relay driver circuits, DC voltage level shifters, and discrete logic inverters requiring stable component supply and long-term obsolescence management.

Supply support for BC309BBU 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 manufacturer specializing in discrete power devices, analog ICs, and interface solutions before its acquisition by ON Semiconductor in 2016.

The BC309BBU belongs to Fairchild's legacy BC307/308/309 family of general-purpose PNP transistors, designed specifically for low-noise amplification and medium-speed switching in consumer, industrial, and educational electronics.

FAQ

What is the h_FE range for BC309BBU?

The BC309BBU is binned as 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 classification ensures consistent biasing behavior across units and simplifies design of stable amplifier and switch circuits without manual transistor sorting. The BC309BBU datasheet confirms this range applies specifically to the BBU suffix variant.

Is BC309BBU suitable for audio amplifier applications?

Yes, BC309BBU is explicitly characterized for low-noise performance: its noise figure is 4 dB at 30–15 kHz under standard test conditions (V_CE = −5 V, I_C = −0.2 mA, R_G = 2 kΩ). This makes BC309BBU appropriate for microphone preamplifiers and other high-fidelity analog signal paths where signal-to-noise ratio is critical - a feature confirmed in the original Fairchild BC307/308/309 datasheet Rev. A2.

What is the maximum collector-emitter voltage rating for BC309BBU?

The BC309BBU has a maximum collector-emitter voltage rating (V_CEO) of −25 V under open-base conditions at T_A = 25°C. This value is distinct from V_CES (−30 V), which applies with base shorted to emitter. Designers must respect the −25 V V_CEO limit in common-emitter configurations to avoid avalanche breakdown - a parameter clearly specified in the Absolute Maximum Ratings table of the BC309BBU datasheet.

Does BC309BBU have a defined saturation voltage?

Yes, BC309BBU specifies two collector-emitter saturation voltages: V_CE(sat) = −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. These values confirm its utility in saturated switching applications such as relay drivers, where low conduction loss is essential. Both points are documented in the Electrical Characteristics table of the official BC309BBU datasheet.

What package type does BC309BBU use?

BC309BBU uses the industry-standard TO-92 plastic package, with dimensions of 3.60 mm (length) × 4.58 mm (width) × 1.02 mm (thickness), and pin configuration: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter. This through-hole package is fully compatible with legacy assembly processes and prototyping breadboards - a mechanical specification confirmed in the Package Dimensions section of the BC309BBU datasheet.