onsemi BC549CG

Overview

BC549CG from onsemi is an NPN general-purpose bipolar junction transistor (BJT) in TO-92 package, with DC current gain (h_FE) of 420–800 at I_C = 2 mA and V_CE = 5 V, maximum collector-emitter voltage V_CEO = 30 V, and continuous collector current I_C = 100 mA. It is commonly used in low-noise audio preamplifier stages and signal switching applications.

For engineers reviewing the BC549CG datasheet, pinout, applications, or equivalent options, key selection considerations include its guaranteed h_FE range, low noise figure (NF ≈ 4 dB at 1 kHz), V_CEO rating, thermal resistance (R_θJA = 200 °C/W), and compatibility with through-hole PCB assembly.

Technical Context

The BC549CG belongs to the BC546–BC550 family of silicon NPN transistors optimized for low-noise amplification and linear switching. Its epitaxial planar structure ensures stable h_FE across temperature and batch variation, with tight gain binning (Group C: h_FE = 420–800).

It operates in active and saturation regions with specified V_CE(sat) ≤ 0.25 V at I_C = 10 mA and I_B = 0.5 mA, and exhibits f_T ≥ 300 MHz - enabling use in audio-frequency and low-speed digital circuits up to ~10 MHz.

Key Specifications

Pinout & Package

BC549CG is housed in a standard TO-92 plastic package with 3 leads. Pin assignment follows JEDEC TO-92 outline: Emitter (pin 1), Base (pin 2), Collector (pin 3), viewed from flat side with leads down.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC549CG, BC547C offers identical packaging and binning but slightly less consistent gain centering, while 2N3904 trades gain precision and noise performance for broader voltage capability and lower cost - making BC549CG optimal for noise-sensitive, gain-stable analog designs.

Availability

BC549CG is available at Aetrix Electronics and suitable for audio preamplifiers, sensor interface circuits, and discrete logic-level switching applications requiring stable component supply and long-term manufacturability.

Supply support for BC549CG 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

onsemi is a global semiconductor leader delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The BC549CG belongs to onsemi's legacy general-purpose transistor product line, designed specifically for reliable, low-cost, low-noise analog signal conditioning and discrete switching in cost-sensitive, high-volume consumer and industrial electronics.

FAQ

What is the maximum collector-emitter voltage rating for BC549CG?

The BC549CG has a maximum collector-emitter voltage (V_CEO) rating of 30 V. This specification defines the highest voltage that can be applied between collector and emitter with the base open, ensuring safe operation in circuits with supply rails up to 24 V. Exceeding this rating risks avalanche breakdown and permanent device failure. The BC549CG datasheet confirms this value under standard test conditions at T_A = 25 °C.

Does BC549CG have a guaranteed h_FE range, and how is it binned?

Yes, BC549CG is binned into Group C with a guaranteed DC current gain (h_FE) range of 420 to 800 when measured at I_C = 2 mA and V_CE = 5 V. This tight binning enables predictable biasing in amplifier and current-source designs without individual calibration. The BC549CG marking "CG" explicitly denotes this Group C gain grade per onsemi's standard transistor coding convention.

Can BC549CG be used in low-noise audio applications?

Yes, BC549CG is specifically characterized for low-noise performance with a typical noise figure (NF) of approximately 4 dB at 1 kHz and I_C = 0.2 mA. Its epitaxial planar construction and Group C binning make it well-suited for microphone preamplifiers, sensor signal conditioning, and other analog front-end stages where signal integrity is critical. The BC549CG datasheet includes noise parameter graphs confirming this behavior.

What is the thermal resistance (R_θJA) of BC549CG, and how does it affect PCB layout?

The BC549CG has a junction-to-ambient thermal resistance (R_θJA) of 200 °C/W in free-air conditions on a standard FR-4 PCB with minimal copper area. This means a 100 mW power dissipation raises the junction temperature by ~20 °C above ambient. For sustained operation above 50 mW, designers should add thermal relief pads or local copper pours - though full heatsinking is rarely needed due to the device's low-power nature. The BC549CG package drawing confirms TO-92 dimensions and thermal test conditions.

Is BC549CG pin-compatible with BC547 or BC550?

Yes, BC549CG shares the identical TO-92 package outline and pinout (E-B-C) with BC547 and BC550, making it mechanically and electrically interchangeable in most circuits. However, gain binning differs: BC547C matches BC549CG's h_FE range, while BC550C offers higher gain (630–1000). Substitution requires verifying whether the target circuit relies on specific gain or noise characteristics - the BC549CG remains optimal where low-noise and mid-range gain stability are prioritized.