onsemi BC546B

Overview

BC546B from ON Semiconductor is an NPN epitaxial silicon transistor designed for general-purpose switching and linear amplification in low-power analog and digital circuits. It delivers V_CEO = 65 V, h_FE = 200–450 (Class B), f_T = 300 MHz, and operates up to 150°C junction temperature - commonly used in audio preamplifiers, relay drivers, and signal conditioning stages.

For engineers reviewing the BC546B datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain range, collector-emitter saturation voltage at defined I_C/I_B, noise figure in low-signal amplification, thermal derating above 25°C, and TO-92 mechanical compatibility with legacy through-hole layouts.

Technical Context

The BC546B is a discrete bipolar junction transistor (BJT) with fixed NPN polarity and planar epitaxial construction. Its base-emitter junction exhibits V_BE(on) = 580–700 mV at I_C = 2 mA, while V_CE(sat) remains ≤250 mV at I_C = 10 mA / I_B = 0.5 mA - enabling efficient low-voltage switching. The device's Cob = 3.5–6.0 pF and f_T = 300 MHz support stable operation in audio-frequency amplifiers and medium-speed digital interfaces.

It belongs to the BC546–BC550 family sharing TO-92 packaging and absolute maximum ratings (e.g., P_C = 500 mW, T_J = 150°C), but differs from BC549/BC550 in higher V_CEO and higher noise figure (NF = 2.0–10.0 dB vs. 1.2–4.0 dB). No integrated biasing, protection, or compensation circuitry is present - external component selection determines operating point stability.

Key Specifications

Pinout & Package

BC546B is housed in a standard JEDEC TO-92 3-lead plastic package with straight leads (bulk/ammo/tape-and-reel variants). Dimensions conform to TO-92 outline drawings per Fairchild Rev. 1.1.1 (2014).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC547B and PN2222A, BC546B uniquely balances 65 V breakdown, Class B h_FE consistency, and TO-92 footprint - making it optimal for cost-sensitive, medium-voltage analog/digital interface designs where pin compatibility and voltage margin are jointly essential.

Availability

BC546B is available at Aetrix Electronics and suitable for audio preamplifiers, relay driver circuits, and LED current switches requiring stable component supply across industrial, consumer, and automotive-qualified production runs.

Supply support for BC546B 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 power management, analog, sensors, and discrete devices for automotive, industrial, and cloud infrastructure markets.

The BC546B belongs to ON Semiconductor's legacy general-purpose transistor product line - engineered for reliability, manufacturability, and broad compatibility in cost-driven, high-volume linear and switching applications.

FAQ

What is the maximum collector-emitter voltage rating for BC546B?

The BC546B has a guaranteed V_CEO (collector-emitter voltage) rating of 65 V under DC conditions at T_A = 25°C. This rating decreases with rising junction temperature and must be derated per the datasheet's safe operating area (SOA) curves. Exceeding 65 V risks avalanche breakdown and permanent device failure - always verify worst-case supply and transient voltages in the final design before selecting BC546B.

Does BC546B have a specified noise figure, and how does it compare to BC549B?

Yes, BC546B has a noise figure (NF) of 2.0–10.0 dB at 1 kHz, V_CE = 5 V, I_C = 200 μA, and R_G = 2 kΩ. In contrast, BC549B specifies NF = 1.4–4.0 dB under identical conditions - reflecting its optimized low-noise epitaxial structure. Use BC546B where moderate noise performance suffices and higher V_CEO is prioritized; choose BC549B only for ultra-low-noise front-end amplification.

What is the h_FE range for BC546B, and how is it binned?

BC546B is factory-binned to h_FE = 200–450 at V_CE = 5 V and I_C = 2 mA - designated as "Class B" per the BC546–BC550 family specification. This binning ensures predictable DC biasing across production lots without individual device characterization. Devices outside this range are sorted into Class A (110–220) or Class C (420–800) and marked accordingly (e.g., BC546A, BC546C).

Is BC546B pin-compatible with BC547B and BC548B?

Yes, BC546B, BC547B, and BC548B share identical TO-92 package dimensions, lead configuration (C-B-E), and pinout - verified by Fairchild's physical dimension diagrams (Fig. 7 & 8, Rev. 1.1.1). However, their absolute maximum ratings differ: BC546B supports V_CEO = 65 V, BC547B = 45 V, and BC548B = 30 V. Swapping them requires verifying voltage stress margins in the target circuit.

What is the typical current gain bandwidth product (f_T) of BC546B, and under what conditions is it measured?

The BC546B has a typical f_T of 300 MHz, measured at V_CE = 5 V, I_C = 10 mA, and frequency = 100 MHz. This parameter defines the unity-gain frequency of the transistor's small-signal current gain (h_fe) and directly impacts high-frequency amplification capability. Actual f_T varies with bias point and temperature - design verification at the intended operating I_C and V_CE is required for RF or fast-switching applications using BC546B.