onsemi BC318C

Overview

BC318C from Fairchild Semiconductor is a PNP epitaxial silicon transistor designed for general-purpose amplification at DC collector currents up to 100 mA, with V_CEO = 20 V, h_FE = 100–800 (at I_C = 2 mA), and V_CE(sat) ≤ 0.5 V (at I_C = 100 mA). It operates across –55 °C to +150 °C and is commonly used in low-power linear amplifier stages and switching circuits in consumer electronics.

For engineers reviewing the BC318C datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package, PNP polarity, DC current gain range, saturation voltage under load, and thermal resistance (R_θJA = 200 °C/W) for board-level thermal design.

Technical Context

The BC318C is a discrete bipolar junction transistor (BJT) fabricated using Fairchild's Process 38, optimized for stable DC amplification and moderate-speed switching. Its epitaxial base structure supports consistent h_FE across temperature and bias conditions, with guaranteed BVCES = 30 V enabling safe operation under transient collector-emitter stress.

It exhibits low output capacitance (C_cb = 4 pF at V_CB = 10 V), supporting use in audio-frequency amplifiers and low-speed digital logic interfaces. The device is not rated for RF or high-frequency switching applications, and its maximum continuous collector current is limited to 100 mA per absolute ratings.

Key Specifications

Pinout & Package

BC318C is housed in a standard TO-92 plastic package with 3 leads. Lead identification follows JEDEC TO-92 outline: Emitter (Lead 1), Base (Lead 2), Collector (Lead 3).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC318C, BC327-40 provides higher voltage and gain but requires re-evaluation of base bias stability, while BC328-40 delivers balanced improvements in V_CEO and h_FE without altering thermal or layout constraints.

Availability

BC318C is available at Aetrix Electronics and suitable for audio pre-amplifier stages, LED driver switches, relay coil drivers, and level-shifting interfaces requiring stable component supply and legacy through-hole compatibility.

Supply support for BC318C 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 power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The BC318C belongs to Fairchild's general-purpose bipolar transistor product line, engineered for cost-effective, reliable amplification and switching in consumer, industrial, and automotive auxiliary circuits.

FAQ

What is the maximum continuous collector current rating for BC318C?

The BC318C has an absolute maximum DC collector current (I_C) rating of 100 mA, as specified in its Fairchild datasheet Rev. 1.0.0. This limit applies at T_C = 25 °C and must be derated under elevated ambient temperatures or pulsed conditions. Exceeding this value risks thermal runaway or permanent degradation of the BC318C's junction integrity.

Is BC318C pin-compatible with BC327 or BC328 series transistors?

Yes, BC318C shares the same TO-92 package and pinout (Emitter–Base–Collector = Pin 1–2–3) with BC327 and BC328 series transistors. However, BC318C differs in V_CEO (20 V vs. 45 V/30 V) and minimum h_FE (100 vs. 250), so direct substitution requires verification of voltage and gain requirements in the target circuit before deploying BC318C.

What is the typical V_CE(sat) of BC318C under switching conditions?

The BC318C exhibits V_CE(sat) ≤ 0.2 V at I_C = 10 mA and I_B = 0.5 mA, and ≤ 0.5 V at I_C = 100 mA and I_B = 5 mA. These values confirm its suitability for low-loss saturated switching in BC318C-based relay drivers or LED controls where power efficiency and thermal rise are design priorities.

Does BC318C support operation at elevated temperatures?

Yes, BC318C is rated for junction and storage temperatures from –55 °C to +150 °C. Its thermal resistance R_θJA = 200 °C/W means that at 100 mA DC collector current and 0.5 V V_CE(sat), junction temperature rise is ~10 °C above ambient-well within safe limits even at 125 °C ambient, provided PCB copper area meets Fairchild's 1.6″ × 1.6″ FR-4 reference layout for BC318C.

Can BC318C be used in audio amplifier designs?

Yes, BC318C is explicitly designed for general-purpose amplifier applications up to 800 mA collector current (per device description), and its low output capacitance (C_cb = 4 pF) and stable h_FE make it suitable for line-level pre-amplifier stages. When used in BC318C-based common-emitter configurations with proper biasing, it delivers low-distortion gain across the 20 Hz–20 kHz audio band without requiring external compensation.