onsemi BC546

Overview

BC546 from ON Semiconductor is a general-purpose NPN epitaxial silicon transistor designed for low-power switching and linear amplification in discrete analog circuits. It delivers V_CEO = 65 V, I_C = 100 mA, P_C = 500 mW, h_FE range of 110–800 (depending on grade), and f_T = 300 MHz - enabling robust operation in voltage-tolerant signal conditioning and relay driver stages.

For engineers reviewing the BC546 datasheet, pinout, applications, or equivalent options, key selection considerations include its high-voltage capability relative to BC547/BC548, TO-92 package constraints, DC gain classification (A/B/C variants), saturation voltage behavior at 10 mA/100 mA, and noise figure suitability for preamplifier front-ends.

Technical Context

The BC546 operates as a single-element bipolar junction transistor with fixed NPN polarity, fabricated using epitaxial base technology for improved gain consistency and frequency response. Its structure supports both active-mode amplification (V_CE ≥ 1 V) and saturated-switching operation (V_CE(sat) ≤ 250 mV at I_C = 100 mA).

It is electrically characterized at T_A = 25°C with absolute maximum ratings including V_CBO = 80 V, V_EBO = 6 V, and T_J = 150°C, and exhibits Cob = 3.5–6.0 pF and Cib = 9 pF - indicating suitability for audio-frequency and low-MHz digital switching where parasitic capacitance must remain minimal.

Key Specifications

Pinout & Package

BC546 is housed in a standard JEDEC TO-92 3-lead plastic package with straight leads (bulk or ammo/tape-and-reel variants). Pin assignment follows the conventional emitter-base-collector (E-B-C) sequence when viewed with flat side facing outward and leads pointing downward.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547 and 2N3904, the BC546 offers superior voltage tolerance for legacy industrial systems while maintaining full compatibility with BC547/BC548 PCB footprints - making it the preferred choice where 65 V breakdown is required without layout change.

Availability

BC546 is available at Aetrix Electronics and suitable for audio pre-amplifiers, microcontroller GPIO drivers, linear voltage regulator pass elements, and signal level shifters requiring stable component supply across long-lifecycle embedded programs.

Supply support for BC546 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

ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power management, analog, and discrete devices for automotive, industrial, and consumer markets.

The BC546 belongs to ON Semiconductor's legacy general-purpose bipolar transistor product line, originally developed by Fairchild and optimized for cost-sensitive, high-reliability linear and switching applications in analog signal chains and interface circuits.

FAQ

What is the maximum collector-emitter voltage rating for BC546?

The BC546 has a guaranteed V_CEO rating of 65 V under DC conditions at T_A = 25°C. This value is specified in the Absolute Maximum Ratings table and defines the upper limit for safe continuous operation without avalanche breakdown. Exceeding this voltage risks permanent device failure. The BC546 datasheet confirms this parameter applies specifically to the BC546 variant - not BC547 or BC548 - and must be derated at elevated ambient temperatures per the thermal resistance curve.

Does BC546 have a defined pinout, and what is the correct orientation?

Yes, BC546 uses the standard TO-92 3-lead package with a fixed pinout: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter - when viewed with the flat side facing forward and leads pointing downward. This orientation is documented in the Physical Dimensions section of the BC546 datasheet and matches industry-standard E-B-C labeling for BC-series transistors. Misalignment during PCB assembly may cause functional failure or damage, so verification against the marking diagram is essential before soldering.

How does BC546 differ from BC547 in terms of electrical performance?

The BC546 differs from BC547 primarily in its higher V_CEO (65 V vs. 45 V) and V_CBO (80 V vs. 50 V), while sharing identical package, pinout, I_C, P_C, h_FE grading, and f_T. These differences make BC546 suitable for applications with higher supply voltages or transient spikes where BC547 would risk breakdown. All other parameters - including V_BE(on), V_CE(sat), and noise figure - are functionally equivalent between the two parts when operated within their respective voltage limits.

Is BC546 suitable for low-noise audio amplification?

Yes, BC546 is suitable for low-noise audio amplification when biased at I_C = 200 μA with R_G = 2 kΩ, delivering a typical noise figure of 2.0–10.0 dB across the 1 kHz band. Its noise performance is comparable to BC547 and better than BC548/BC549 in this configuration. However, for ultra-low-noise applications (<1.5 dB), BC549 or BC550 should be selected instead, as they are explicitly optimized for low-noise operation per the BC546/BC547/BC548/BC549/BC550 datasheet.

What are the available gain grades for BC546, and how are they marked?

The BC546 is offered in three h_FE grades: A (110–220), B (200–450), and C (420–800), each identified by a suffix letter in the full part number (e.g., BC546A, BC546B, BC546C) and corresponding laser marking on the device body (e.g., "A", "B", or "C"). These grades allow designers to select consistent DC current gain for stable biasing in amplifier circuits or predictable switching thresholds in digital logic interfaces - critical for production yield and performance repeatability.