onsemi BC308C

Overview

BC308C from Fairchild Semiconductor is a PNP epitaxial silicon transistor designed for low-noise amplifier and switching applications, with V_CEO = −25 V, I_C = −100 mA, P_C = 500 mW, h_FE = 380–800 (Class C), and TO-92 package. It operates in audio preamplifier stages and relay driver circuits where moderate gain and low saturation voltage are required.

For engineers reviewing the BC308C datasheet, pinout, applications, or equivalent options, key selection considerations include its Class C h_FE range, −25 V V_CEO, −0.3 V V_CE(sat) at I_C = −100 mA, noise figure of 4 dB (f = 30–15 kHz), and TO-92 mechanical compatibility with legacy through-hole designs.

Technical Context

The BC308C is a discrete PNP bipolar junction transistor optimized for linear amplification and saturated switching. Its h_FE classification (C: 380–800) ensures consistent current gain across production lots, while f_T = 130 MHz supports audio-frequency signal integrity without high-frequency roll-off.

It features low V_CE(sat) (−0.3 V @ I_C = −100 mA, I_B = −5 mA) and V_BE(sat) (−0.85 V under same conditions), enabling efficient operation in low-voltage DC control paths. Its Cob = 6 pF and Cib = 12 pF support stable biasing in high-impedance amplifier nodes.

Key Specifications

Pinout & Package

BC308C is housed in a standard TO-92 plastic package with 3 leads, compatible with manual soldering and wave-solder processes. Lead spacing and body dimensions conform to JEDEC TO-92 outline (3.60 ±0.20 mm width, 4.58 +0.25/−0.15 mm height).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC327-40 and PN2907A, BC308C delivers superior noise performance (4 dB vs. unspecified) and tighter h_FE binning (380–800), making it uniquely suitable for audio preamplification and precision linear control where signal fidelity is critical.

Availability

BC308C is available at Aetrix Electronics and suitable for audio preamplifier design, relay driver implementation, and LED dimming control requiring stable component supply, long-term obsolescence management, and traceable sourcing.

Supply support for BC308C 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 devices before its acquisition by ON Semiconductor in 2016.

The BC307/308/309 family was developed for general-purpose PNP amplification and switching in consumer, industrial, and instrumentation systems where reliability, gain consistency, and low-noise operation were prioritized.

FAQ

What is the maximum collector-emitter voltage rating for BC308C?

The BC308C has a guaranteed V_CEO rating of −25 V at T_A = 25°C, meaning it can safely sustain up to 25 volts reverse bias between collector and emitter in common-emitter configuration without breakdown. This value is confirmed in the Absolute Maximum Ratings table of the official Fairchild datasheet Rev. A2 (August 2002). Exceeding this voltage risks permanent device failure. The BC308C datasheet also specifies a higher V_CES of −30 V under open-base conditions.

Is BC308C suitable for low-noise audio amplifier applications?

Yes, BC308C is explicitly characterized for low-noise operation: its datasheet specifies a noise figure of 4 dB at V_CE = −5 V, I_C = −0.2 mA, R_G = 2 kΩ, and f = 30–15 kHz - matching typical voice-band and mid-audio frequencies. This measured value, combined with its Class C h_FE binning, makes BC308C appropriate for microphone preamplifiers and line-level gain stages where signal integrity is essential. The BC308C datasheet confirms this performance under defined test conditions.

What is the pin configuration of BC308C in the TO-92 package?

The BC308C uses the standard TO-92 pinout: Pin 1 is Collector, Pin 2 is Base, and Pin 3 is Emitter - verified in the "BC307/308/309" datasheet Figure "Package Dimensions" and "Switching and Amplifier Applications" section. This arrangement is identical across the BC307/308/309 family and matches industry-standard PNP TO-92 orientation when viewed with flat side facing the user and leads pointing downward. No alternate pinouts are documented for BC308C.

How does the h_FE classification of BC308C differ from BC307 and BC309?

BC308C belongs to Class C (h_FE = 380–800), whereas BC307 is Class A (120–220) and BC309 is also Class C but specified for low-noise operation with distinct noise testing. All three share identical absolute maximum ratings and package, but BC308C offers the highest guaranteed gain range among standard variants. The BC308C datasheet confirms this classification in the "Electrical Characteristics" table under "h_FE Classification", and no cross-class substitution is recommended without circuit validation.

What is the typical saturation voltage of BC308C under full-rated current?

The BC308C exhibits V_CE(sat) = −0.3 V when operated at I_C = −100 mA and I_B = −5 mA, as specified in the "Electrical Characteristics" table. This low saturation voltage reduces power dissipation in switching applications and improves efficiency in relay or LED driver circuits. The value is measured under defined DC conditions and is consistent across the Class C bin. The BC308C datasheet further lists −0.5 V at lower current (I_C = −10 mA), confirming its strong saturation behavior across operating range.