onsemi BC559

Overview

BC559 from onsemi is a PNP epitaxial silicon transistor optimized for low-noise amplification and general-purpose switching, with V_CEO = −30 V, I_C = −100 mA, and noise figure of 1.2–4.0 dB at 30–15 kHz. It operates in TO-92-3 (case 135AR) packaging and serves as a complement to BC546–BC550 NPN devices in audio preamplifier stages and signal conditioning circuits.

For engineers reviewing the BC559 datasheet, pinout, applications, or equivalent options, key selection criteria include its low-noise performance at 200 µA collector current, −30 V V_CEO rating, TO-92 mechanical compatibility, h_FE range of 420–800 (Class C), and RoHS-compliant Pb-free construction.

Technical Context

The BC559 is a discrete PNP bipolar junction transistor designed for linear amplification and switching in low-power analog circuits. Its low-noise specification (NF = 1.2–4.0 dB) is validated under V_CE = −5 V, I_C = −200 µA, R_G = 2 kΩ, and f = 30–15,000 Hz - distinct from BC556/557/558 variants rated only up to 1 kHz.

It shares the same TO-92-3 package (case 135AR) and absolute maximum ratings as BC558 and BC560, but differs in noise performance and h_FE classification: BC559C delivers h_FE = 420–800, while BC560C offers tighter gain consistency and lower NF (1.2–2.0 dB).

Key Specifications

Pinout & Package

BC559 is housed in a TO-92-3 plastic package (case 135AR), with leads arranged in straight or lead-formed configurations per ordering variant (e.g., BC559BTA). The device uses standard through-hole mounting and conforms to JEDEC TO-92 mechanical dimensions (4.83 mm × 4.76 mm).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC559C (same part, higher-gain bin) and BC560C (lower-noise sibling), the BC559 offers the best balance of cost, availability, and verified 1.2 dB minimum noise performance for mainstream low-noise amplification tasks without over-specifying.

Availability

BC559 is available at Aetrix Electronics and suitable for audio preamplification, discrete signal conditioning, and low-power switching applications requiring stable component supply and long-term industrial availability.

Supply support for BC559 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 manufacturer specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC559 belongs to onsemi's legacy general-purpose transistor product line, engineered specifically for cost-sensitive, high-reliability analog signal chain applications where low noise, predictable gain, and TO-92 compatibility are essential.

FAQ

What is the maximum collector-emitter voltage rating for BC559?

The BC559 has a maximum collector-emitter voltage (V_CEO) rating of −30 V at T_A = 25°C. This rating applies to the BC558/BC559/BC560 group and defines the upper limit for safe operation in common-emitter configurations. Exceeding this voltage risks avalanche breakdown and permanent device damage. Derating is required above 25°C ambient per the thermal characteristics table in the official onsemi datasheet for BC559.

Is BC559 suitable for low-noise audio amplifier designs?

Yes, BC559 is explicitly specified for low-noise operation with a noise figure of 1.2–4.0 dB at V_CE = −5 V, I_C = −200 µA, R_G = 2 kΩ, and f = 30–15,000 Hz. This makes BC559 appropriate for microphone preamplifiers, sensor signal conditioning, and other audio front-end stages where preserving signal-to-noise ratio is critical. Its performance is validated in the onsemi BC556–BC560 datasheet Rev. 3 (June 2024).

What package type does BC559 use and how are its pins arranged?

BC559 uses the TO-92-3 plastic package (case 135AR), with standardized lead-forming for through-hole PCB assembly. When viewing the flat side of the package with leads pointing downward, pin 1 (left) is Collector, pin 2 (center) is Base, and pin 3 (right) is Emitter. This pinout is confirmed in the onsemi mechanical drawings 98AON13879G and the marking diagram on page 1 of the BC556–BC560 datasheet.

How does BC559 differ from BC556 in terms of voltage rating and application focus?

BC559 has V_CEO = −30 V and is optimized for low-noise amplification, whereas BC556 offers V_CEO = −65 V and targets high-voltage switching applications. Their noise figures differ significantly: BC559 specifies 1.2–4.0 dB up to 15 kHz, while BC556 is rated only at 1 kHz (2–10 dB). These distinctions make BC559 unsuitable as a drop-in replacement for BC556 in high-voltage circuits, and vice versa in noise-critical analog stages.

What h_FE gain classification does BC559 support and how is it marked?

BC559 supports Class A (110–220), Class B (200–450), and Class C (420–800) h_FE bins, with BC559C being the highest-gain variant. Devices are marked with "BC559C" on the package body for Class C units. Gain classification is tested per the onsemi datasheet conditions: V_CE = −5 V, I_C = −2 mA. Selection of BC559C ensures minimum h_FE ≥ 420 for stable biasing in production designs.