onsemi BC559B

Overview

BC559B from onsemi is a PNP epitaxial silicon transistor optimized for low-noise amplification and general-purpose switching in analog and signal-conditioning circuits, with V_CEO = −30 V, h_FE = 200–450 (Class B), f_T = 150 MHz, and V_BE(on) = −600 to −750 mV at I_C = −2 mA - used in audio preamplifiers, sensor interface stages, and discrete bias networks.

For engineers reviewing the BC559B datasheet, pinout, applications, or equivalent options, key selection criteria include its low-noise performance (NF = 1.2–4.0 dB at 30–15 kHz), TO-92-3 package compatibility, complementary pairing with BC549/BC550, and Class B h_FE binning for consistent gain matching in differential pairs.

Technical Context

The BC559B operates as a medium-speed, low-noise PNP bipolar junction transistor with fixed-emitter configuration, designed for linear amplification where noise figure and gain consistency are critical. Its h_FE classification (B: 200–450) ensures predictable current amplification across production lots, and its f_T of 150 MHz supports audio and sub-RF signal paths.

Thermal design is constrained by R_JA = 250 °C/W and P_D = 500 mW at 25°C, with 4.0 mW/°C derating above ambient - requiring minimal heatsinking in PCB-mounted TO-92 layouts. The device exhibits low C_ob = 6 pF and tight V_CE(sat) = −250 to −650 mV at I_C = −100 mA, enabling efficient switching in low-power logic interfaces.

Key Specifications

Pinout & Package

BC559B is housed in a TO-92-3 plastic package (Case 135AR), lead-formed, with standard through-hole mounting and thermal dissipation rated at 500 mW at 25°C ambient.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC559C and BC558B, BC559B delivers optimal balance of noise performance (1.2–4.0 dB), gain consistency (200–450), and bandwidth (150 MHz) for audio and sensor signal chains - making it the preferred choice where fidelity and repeatability are prioritized over maximum gain or lowest cost.

Availability

BC559B is available at Aetrix Electronics and suitable for audio preamplifiers, sensor interface circuits, and discrete bias networks requiring stable component supply, long-term manufacturability, and RoHS-compliant through-hole assembly.

Supply support for BC559B 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 (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power, analog, sensing, and connectivity solutions for automotive, industrial, and consumer markets.

The BC559B belongs to onsemi's legacy BC5xx PNP/NPN transistor family, engineered for reliability and consistency in analog signal path design - particularly where low-noise, gain-matched discrete transistors are required in cost-sensitive, high-volume applications.

FAQ

What is the maximum collector-emitter voltage rating for BC559B?

The BC559B has a maximum collector-emitter voltage (V_CEO) rating of −30 V. This value is confirmed in the Absolute Maximum Ratings table of the official onsemi datasheet (Rev. 3, June 2024). Exceeding this voltage risks avalanche breakdown and permanent device damage. Designers must ensure that the BC559B operates within this limit under all static and transient conditions in the target circuit.

Is BC559B suitable for low-noise audio amplification?

Yes, BC559B is explicitly characterized for low-noise performance with a noise figure (NF) of 1.2–4.0 dB at 30–15,000 Hz, measured at V_CE = −5 V, I_C = −200 µA, and R_G = 2 kΩ. This specification makes the BC559B appropriate for microphone preamplifiers, phono stages, and other sensitive analog front-ends where signal integrity is critical - a key differentiator from standard switching transistors.

What h_FE range does BC559B have, and how is it binned?

The BC559B is binned to h_FE Class B, with a guaranteed DC current gain range of 200–450 at V_CE = −5 V and I_C = −2 mA. This binning is documented in the h_FE Classification table of the onsemi datasheet and enables predictable gain behavior in production assemblies - especially valuable in matched-pair configurations such as differential amplifiers or current mirrors using BC559B.

Does BC559B have the same pinout as BC549B?

Yes, BC559B and BC549B share identical TO-92-3 pinouts (Collector-Base-Emitter on pins 1-2-3 respectively) and are designed as complementary PNP/NPN pairs. This pin compatibility is confirmed in the Marking Diagram and Ordering Information sections of the onsemi datasheet, enabling direct substitution in push-pull, phase-splitter, and level-shift circuits without PCB modification.

What is the thermal resistance and power dissipation capability of BC559B?

The BC559B has a thermal resistance from junction-to-ambient (R_JA) of 250 °C/W and a maximum total device dissipation (P_D) of 500 mW at T_A = 25°C, with a derating factor of 4.0 mW/°C above that temperature. These values assume standard FR-4 PCB layout per the datasheet's thermal test condition (76 mm × 114 mm board), and define safe continuous operation limits for through-hole mounted BC559B in ambient temperatures up to +85°C.