onsemi BC550_J35Z

Overview

BC550_J35Z from ON Semiconductor is an NPN epitaxial silicon transistor optimized for low-noise amplification and general-purpose switching in analog signal paths. It features VCEO = 45 V, hFE = 420–800 (Class C), fT = 300 MHz, and NF = 1.4–3.0 dB at 1 kHz with IC = 200 μA, commonly used in audio preamplifiers and sensor interface stages.

For engineers reviewing the BC550_J35Z datasheet, pinout, applications, or equivalent options, key selection criteria include noise figure, DC current gain linearity at low collector currents, VCEO derating in high-impedance bias networks, and TO-92 thermal resistance under continuous 100 mA operation.

Technical Context

This device operates as a discrete bipolar junction transistor with fixed emitter-base and collector-base junction geometries defined by Fairchild's legacy BC5xx process. Its low-noise performance stems from optimized base doping and epitaxial layer thickness, enabling stable hFE ≥ 420 at IC = 2 mA and VCE = 5 V.

The BC550_J35Z shares absolute maximum ratings and thermal limits with the BC546–BC549 family but distinguishes itself via tighter hFE classification (C-grade) and lower noise figure-specifically rated at 1.4–3.0 dB under standardized 2 kΩ source impedance and 1 kHz test conditions.

Key Specifications

Pinout & Package

BC550_J35Z is housed in a standard JEDEC TO-92 3-lead plastic package with straight leads (bulk packing). Thermal resistance θJA is 200°C/W, requiring board-level copper area for sustained >50 mA operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC549C and 2N5551, BC550_J35Z delivers the narrowest noise figure (1.4–3.0 dB) and highest guaranteed hFE (420–800) within the BC5xx family, making it optimal for low-level analog amplification where signal integrity is critical.

Availability

BC550_J35Z is available at Aetrix Electronics and suitable for audio preamplifier design, sensor signal conditioning, and general-purpose discrete switching requiring stable component supply and long-term obsolescence management.

Supply support for BC550_J35Z 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 applications.

The BC550_J35Z belongs to ON Semiconductor's legacy general-purpose transistor product line, originally developed by Fairchild Semiconductor to deliver reliable, low-cost NPN amplification and switching in cost-sensitive analog and mixed-signal systems.

FAQ

What is the maximum collector-emitter voltage rating for BC550_J35Z?

The BC550_J35Z has a maximum collector-emitter voltage (VCEO) rating of 45 V. This value is specified under standard test conditions at TA = 25°C and defines the upper limit for safe DC operation between collector and emitter terminals. Exceeding this voltage risks avalanche breakdown and permanent device damage. Designers must ensure that transient spikes and steady-state voltages in the target circuit remain within this limit, especially in inductive load switching or high-impedance bias networks.

Does BC550_J35Z have a guaranteed noise figure specification?

Yes, BC550_J35Z has a guaranteed noise figure (NF) of 1.4–3.0 dB, measured at VCE = 5 V, IC = 200 μA, f = 1 kHz, and RG = 2 kΩ. This specification is explicitly documented in the original Fairchild BC546–BC550 datasheet and remains valid for BC550_J35Z as a Class C variant. The narrow NF range reflects process-controlled base doping and epitaxial layer uniformity, making BC550_J35Z suitable for low-noise analog front ends where signal-to-noise ratio is critical.

What is the hFE classification for BC550_J35Z and how is it verified?

BC550_J35Z is classified as Class C, with a guaranteed DC current gain (hFE) range of 420–800 at VCE = 5 V and IC = 2 mA. This classification is confirmed by production binning per the BC546–BC550 family datasheet Rev. 1.1.1. Each BC550_J35Z unit undergoes parametric testing during manufacturing to ensure hFE falls within this window, enabling predictable bias point stability in amplifier and switching circuits without additional gain-setting feedback components.

Is BC550_J35Z pin-compatible with other BC5xx transistors?

Yes, BC550_J35Z uses the standard TO-92 3-lead package with pin configuration 1 = Collector, 2 = Base, 3 = Emitter - identical to BC546, BC547, BC548, BC549, and complementary PNP types like BC556–BC560. This mechanical and electrical pinout compatibility allows direct substitution in existing PCB layouts designed for any BC5xx-series NPN transistor, provided VCEO, hFE, and noise requirements align with the application's functional needs.

What thermal limitations apply to BC550_J35Z in continuous operation?

BC550_J35Z has a maximum junction temperature (TJ) of 150°C and a thermal resistance from junction-to-ambient (θJA) of 200°C/W in the standard TO-92 package. At ambient temperatures up to 70°C, continuous power dissipation must be limited to ≤400 mW to maintain TJ ≤ 150°C. For sustained 100 mA collector current, designers must verify VCE × IC stays below this threshold and consider adding copper pour or airflow if operating near thermal limits.