onsemi BC549C

Overview

BC549C from onsemi is an NPN general-purpose bipolar junction transistor (BJT) optimized for low-noise amplification in audio and signal conditioning circuits, with DC current gain (h_FE) of 420–800 at I_C = 2 mA, V_CE = 5 V, maximum collector-emitter voltage V_CEO = 30 V, continuous collector current I_C = 100 mA, and transition frequency f_T = 300 MHz - used in preamplifier stages of portable audio devices and sensor interface front-ends.

For engineers reviewing the BC549C datasheet, pinout, applications, or equivalent options, key selection considerations include its guaranteed h_FE range, low noise figure (NF ≈ 4 dB at 1 kHz), TO-92 package thermal resistance (R_θJA = 200 °C/W), and compatibility with common emitter biasing configurations in discrete analog signal chains.

Technical Context

The BC549C operates as a silicon NPN BJT with epitaxial base construction, enabling stable gain and low leakage across industrial temperature range (−55 °C to +150 °C). Its h_FE binning (C-grade) ensures tight current gain distribution, and its f_T supports high-fidelity audio bandwidth extension beyond 20 kHz without phase distortion.

It features low saturation voltage (V_CE(sat) ≤ 0.25 V at I_C = 10 mA, I_B = 0.5 mA), making it suitable for linear switching and Class-A amplifier topologies where efficiency and linearity are jointly prioritized over power density.

Key Specifications

Pinout & Package

BC549C is housed in a standard through-hole TO-92 plastic package (JEDEC TO-92AB), with lead spacing of 0.4 inch (10.16 mm) and body dimensions of 4.6 × 3.3 × 4.0 mm. Thermal performance is characterized by R_θJA = 200 °C/W under free-air conditions.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC549C, BC547C offers higher voltage headroom with identical gain and noise performance, while 2N3904 trades gain consistency and noise for broader availability and lower cost - making BC549C optimal for noise-sensitive, mid-voltage analog amplification where h_FE predictability is essential.

Availability

BC549C is available at Aetrix Electronics and suitable for audio preamplification, sensor signal conditioning, and low-power linear switching applications requiring stable component supply and consistent parametric performance across production lots.

Supply support for BC549C 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 supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The BC549C belongs to onsemi's legacy general-purpose transistor family designed specifically for high-fidelity analog signal amplification and robust discrete switching in cost-sensitive, space-constrained consumer and industrial electronics.

FAQ

What is the maximum collector-emitter voltage rating for BC549C?

The BC549C has a maximum collector-emitter voltage (V_CEO) rating of 30 V. This specification defines the highest voltage that can be safely applied between collector and emitter with the base open, and it determines the BC549C's suitability for circuits operating up to 24 V DC rails. Exceeding this rating risks avalanche breakdown and permanent device failure. The BC549C datasheet confirms this value under standard test conditions (T_A = 25 °C).

Does BC549C support audio-frequency amplification?

Yes, BC549C supports audio-frequency amplification with verified performance up to 20 kHz and beyond. Its 300 MHz transition frequency (f_T) and 4 dB noise figure at 1 kHz make it well-suited for low-noise preamplifier stages in electret microphone circuits and line-level signal buffers. The BC549C's h_FE consistency across the C-grade bin further ensures stable gain in Class-A audio amplifier designs.

What is the typical DC current gain (h_FE) range for BC549C?

The BC549C has a guaranteed DC current gain (h_FE) range of 420 to 800 when tested at I_C = 2 mA and V_CE = 5 V. This tight binning distinguishes the "C" suffix variant from BC549A (110–220) and BC549B (200–450), enabling predictable biasing in production-grade analog circuits without individual gain adjustment. onsemi's official datasheet specifies this range for all BC549C units.

Is BC549C available in surface-mount packaging?

No, BC549C is only offered in the through-hole TO-92AB package per onsemi's official product documentation. There is no SMD variant (e.g., SOT-23 or SC-59) designated as BC549C. Engineers requiring surface-mount compatibility should consider functional alternatives such as MMBT549C (SOT-23) - which shares identical electrical specifications but differs in thermal and mechanical characteristics due to package geometry.

How does BC549C compare to BC547C in terms of voltage rating?

BC549C has a V_CEO rating of 30 V, whereas BC547C is rated for 45 V. Both share identical h_FE (420–800), f_T (300 MHz), and noise performance. The higher voltage rating of BC547C makes it preferable in 36 V or 48 V nominal systems, while BC549C remains optimal for ≤24 V applications where tighter thermal resistance and proven legacy qualification are priorities. onsemi documents both ratings in their respective datasheets.