onsemi BC308BTA

Overview

BC308BTA from Fairchild Semiconductor is a PNP epitaxial silicon transistor designed for low-noise amplifier and general-purpose switching applications, with V_CEO = −25 V, I_C = −100 mA, P_C = 500 mW, h_FE (Class B) = 180–460, and TO-92 package. It operates in audio preamplifier stages, relay drivers, and level-shifting circuits where moderate gain and reliable saturation are required.

For engineers reviewing the BC308BTA datasheet, pinout, applications, or equivalent options, key selection criteria include its PNP polarity, −25 V V_CEO, Class B h_FE range, TO-92 mechanical compatibility, and verified performance at I_C = −2 mA and V_CE = −5 V.

Technical Context

The BC308BTA is a discrete bipolar junction transistor (BJT) with fixed PNP topology, optimized for linear amplification and saturated switching. Its h_FE classification (B) guarantees DC current gain between 180 and 460 at V_CE = −5 V and I_C = −2 mA, and its f_T of 130 MHz supports mid-frequency small-signal amplification up to ~10 MHz in practical designs.

It features low V_CE(sat) (−0.5 V at I_C = −10 mA / I_B = −0.5 mA), low noise figure (2 dB at 1 kHz, RG = 2 kΩ), and tight parameter grouping across production lots-enabling consistent biasing in multi-stage analog circuits without individual trimming.

Key Specifications

Pinout & Package

BC308BTA is housed in a standard TO-92 plastic package with 3 leads, compatible with through-hole PCB assembly and manual prototyping. Lead spacing and body dimensions conform to JEDEC TO-92 outline (3.60 mm × 4.58 mm × 4.58 mm max).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC308BTA, BC327-25 offers greater voltage headroom but reduced noise immunity, while PN2907A provides wider safety margin at the cost of undocumented noise performance-making BC308BTA the optimal choice for precision low-noise amplification within its −25 V operating window.

Availability

BC308BTA is available at Aetrix Electronics and suitable for audio preamplifiers, relay driver modules, and level-shifting interfaces requiring stable component supply, long-lifecycle support, and consistent parametric binning.

Supply support for BC308BTA 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 BC307/308/309 family was developed as a standardized series of general-purpose PNP transistors targeting cost-sensitive, high-volume analog and switching applications in consumer and industrial electronics.

FAQ

What is the maximum collector-emitter voltage rating for BC308BTA?

The BC308BTA has a guaranteed V_CEO rating of −25 V at T_A = 25°C, meaning it can safely block up to 25 V in reverse bias between collector and emitter with base open. This value is confirmed in the Absolute Maximum Ratings table and applies specifically to the BC308 and BC309 variants-not the BC307. Exceeding this voltage risks avalanche breakdown and permanent device failure.

Is BC308BTA suitable for low-noise audio amplifier designs?

Yes, BC308BTA is validated for low-noise operation with a specified noise figure of 2 dB at 1 kHz under standard test conditions (V_CE = −5 V, I_C = −0.2 mA, R_G = 2 kΩ). This makes BC308BTA appropriate for first-stage microphone preamplifiers and other sensitive analog signal paths where SNR preservation is critical.

What does the "B" suffix in BC308BTA indicate?

The "B" in BC308BTA denotes the h_FE gain classification bin: Class B corresponds to a guaranteed DC current gain range of 180–460 at V_CE = −5 V and I_C = −2 mA. This binning enables predictable bias design without unit-by-unit characterization and distinguishes it from BC308ATA (Class A: 120–220) and BC308CTA (Class C: 380–800).

Can BC308BTA be used as a direct replacement for BC308?

Yes, BC308BTA is a fully compatible variant of the BC308 transistor with identical electrical specifications, TO-92 package, and pinout. The "TA" suffix indicates tape-and-reel packaging per JEDEC standards, while the "B" specifies the h_FE bin-both functionally and mechanically interchangeable with legacy BC308 parts in existing designs.

What is the typical saturation voltage of BC308BTA under switching conditions?

The BC308BTA exhibits a typical V_CE(sat) of −0.5 V when operated with I_C = −10 mA and I_B = −0.5 mA, confirming strong saturation behavior. At higher currents (I_C = −100 mA, I_B = −5 mA), V_CE(sat) drops further to −0.3 V-enabling efficient low-loss switching in relay and LED driver applications up to its 100 mA rating.