onsemi BC550

Overview

BC550 from ON Semiconductor is a low-noise NPN epitaxial silicon transistor designed for small-signal amplification in audio and RF front-end stages, with VCEO = 45 V, IC = 100 mA, and noise figure as low as 1.4 dB at 1 kHz (RG = 2 kΩ). It operates in TO-92 package with collector-base voltage rating of 50 V and junction temperature up to 150°C.

For engineers reviewing the BC550 datasheet, pinout, applications, or equivalent options, this part is selected for low-noise analog gain where hFE ≥ 420 (Class C), fT = 300 MHz, and Cob ≤ 6.0 pF are critical - especially in preamplifier, oscillator, and signal conditioning circuits requiring stable DC current gain and minimal broadband noise.

Technical Context

The BC550 is a discrete bipolar junction transistor optimized for low-noise amplification, not switching. Its hFE classification (C-grade: 420–800) and NF specification (1.4–3.0 dB) are explicitly defined for VCE = 5 V, IC = 200 μA, RG = 2 kΩ, f = 1 kHz - distinguishing it from BC546/BC547 high-voltage variants and BC549 mid-noise counterparts.

It shares the same TO-92 3L mechanical form factor and terminal assignment (Collector–Base–Emitter, pins 1–2–3) across the BC546–BC550 family but differs in absolute maximum ratings (e.g., VCEO = 45 V vs. 65 V for BC546) and electrical characterization conditions - confirming its dedicated role in precision analog signal paths rather than general-purpose switching.

Key Specifications

Pinout & Package

BC550 is housed in a JEDEC-standard TO-92 3-lead molded plastic package with straight leads (bulk or ammo/tape-and-reel variants), rated for 500 mW power dissipation and operating from –65°C to +150°C.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise NPN transistor applications.

Compared with BC549C and 2N5088, the BC550 offers the optimal balance of low noise (1.4 dB min), high voltage capability (45 V), and tight hFE distribution (420–800) - making it preferred for industrial audio front-ends and RF buffer designs requiring both headroom and repeatability.

Availability

BC550 is available at Aetrix Electronics and suitable for audio preamplifier circuits, crystal oscillator buffering, and RF front-end amplification requiring stable component supply, consistent hFE grading, and verified low-noise performance across production volumes.

Supply support for BC550 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 (formerly Fairchild Semiconductor) is a global semiconductor manufacturer specializing in power management, analog, and discrete devices for automotive, industrial, and consumer applications.

The BC550 belongs to ON Semiconductor's legacy general-purpose bipolar transistor product line, engineered specifically for low-noise small-signal amplification in cost-sensitive, high-reliability analog systems.

FAQ

What is the maximum collector-emitter voltage rating for BC550?

The BC550 has a maximum collector-emitter voltage (VCEO) rating of 45 V at TA = 25°C. This value is confirmed in the Absolute Maximum Ratings table of the official ON Semiconductor datasheet (Rev. 1.1.1). Exceeding this voltage risks permanent device breakdown. Derating is required above 25°C ambient per the datasheet's thermal curves. The BC550 is not rated for 65 V like the BC546 variant.

Is BC550 pin-compatible with BC547 or BC549?

Yes, the BC550 is pin-compatible with BC547 and BC549 - all share identical TO-92 3L packaging with Collector/Base/Emitter assigned to pins 1/2/3 respectively. However, substitution requires verification of application-specific parameters: BC550 offers lower noise (1.4–3.0 dB) and higher hFE (Class C) than BC547B, but lower VCEO (45 V vs. 45 V for BC547, 30 V for BC549). The BC550 should not replace BC546 in 65 V applications.

What hFE classification does BC550 carry, and how is it marked?

The BC550 is manufactured in Class C hFE grade (420–800), as specified in the hFE Classification table of the datasheet. Units are marked "BC550C" on the package body - for example, BC550CBU (bulk) and BC550CTA (ammo). This distinguishes it from BC550A (110–220) or BC550B (200–450), though only the C-grade is documented as low-noise in the "Features" section and noise table.

Does BC550 support RF applications up to what frequency?

The BC550 has a current gain–bandwidth product (fT) of 300 MHz under standard test conditions (VCE = 5 V, IC = 10 mA, f = 100 MHz). This enables practical RF amplification up to approximately 30–50 MHz with usable gain; for 433 MHz or 868 MHz ISM band use, it functions effectively as a buffer or driver where gain requirements are modest and impedance matching is applied. Its Cob ≤ 6.0 pF helps preserve stability in tuned circuits.

How does BC550 differ from BC549 in low-noise performance?

The BC550 specifies a tighter noise figure range (1.4–3.0 dB) versus BC549 (1.4–4.0 dB) at 1 kHz, VCE = 5 V, IC = 200 μA, RG = 2 kΩ - indicating superior consistency in low-noise applications. Both are labeled "Low-Noise" in the datasheet features, but BC550's lower maximum NF and shared Class C hFE grading make it the preferred choice for high-fidelity preamplifier designs where worst-case noise margin is critical.