onsemi BC558B_J18Z

Overview

BC558B_J18Z from onsemi is a PNP epitaxial silicon transistor designed for linear amplification and switching in low-power analog and digital circuits, with V_CEO = −30 V, I_C = −100 mA, h_FE = 200–450 (Class B), f_T = 150 MHz, and TO-92-3 package. It serves as a complement to BC546–BC550 NPN transistors in push-pull stages, bias networks, and signal conditioning blocks.

For engineers reviewing the BC558B_J18Z datasheet, pinout, applications, or equivalent options, key selection criteria include verified V_CEO/V_CBO ratings, h_FE classification consistency, thermal derating behavior, and TO-92 leadform compatibility with legacy PCB footprints.

Technical Context

This device operates as a general-purpose PNP bipolar junction transistor with fixed-emitter biasing capability and DC current gain controlled by base current injection. Its −30 V V_CEO and −30 V V_CBO ratings define safe operation in low-voltage negative-rail circuits, while its 150 MHz f_T supports audio-frequency amplification and moderate-speed switching up to ~10 MHz.

Thermal performance is governed by R_JA = 250 °C/W on standard FR-4 PCBs, requiring derating above 25°C at 4.0 mW/°C. The device exhibits low noise (NF = 2–10 dB at 1 kHz) and stable h_FE across −55°C to +150°C junction temperature range.

Key Specifications

Pinout & Package

BC558B_J18Z is housed in a TO-92-3 plastic package (Case 135AR), with standardized leadform: lead 1 = Collector, lead 2 = Base, lead 3 = Emitter. Dimensions are 4.83 mm × 4.76 mm × 3.6 mm, compatible with industry-standard through-hole mounting and wave-soldering processes.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC557B and BC559B, BC558B_J18Z provides the most consistent trade-off between voltage rating, noise performance, and h_FE uniformity-making it the default choice for cost-sensitive, mid-voltage analog and logic interface applications where −30 V operation suffices.

Availability

BC558B_J18Z is available at Aetrix Electronics and suitable for audio preamplifiers, discrete logic inverters, current mirror references, and LED driver switches requiring stable component supply and long-term obsolescence mitigation.

Supply support for BC558B_J18Z 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 manufacturer specializing in energy-efficient power management, analog, and sensing solutions for automotive, industrial, and cloud infrastructure markets.

The BC556–BC560 family was engineered for high-reliability, low-cost discrete signal conditioning in consumer and industrial equipment-emphasizing parameter consistency, thermal robustness, and RoHS compliance across decades of production.

FAQ

What is the maximum collector-emitter voltage rating for BC558B_J18Z?

The BC558B_J18Z has a guaranteed V_CEO rating of −30 V at T_A = 25°C, meaning it can safely operate with up to 30 V reverse potential between collector and emitter terminals. Exceeding this value risks avalanche breakdown and permanent damage. Derating is not specified beyond absolute maximum limits, so design margins should maintain at least 20% headroom in production circuits.

Is BC558B_J18Z pin-compatible with other BC5xx PNP transistors?

Yes, BC558B_J18Z uses the standard TO-92-3 (Case 135AR) package with pin 1 = Collector, pin 2 = Base, pin 3 = Emitter-identical to BC556, BC557, BC559, and BC560 variants. This allows direct substitution in existing footprints, though electrical parameters (e.g., V_CEO, NF) differ and must be verified per application.

What h_FE range does BC558B_J18Z guarantee?

BC558B_J18Z is classified as Class B, guaranteeing a DC current gain (h_FE) between 200 and 450 when measured at V_CE = −5 V and I_C = −2 mA. This range is confirmed in the onsemi datasheet and applies to all units marked "BC558B" regardless of date code or packaging format, including BC558B_J18Z.

Does BC558B_J18Z support high-frequency signal amplification?

Yes, BC558B_J18Z has a current gain bandwidth product (f_T) of 150 MHz, enabling effective amplification of signals up to approximately 10 MHz in common-emitter configurations. Its 6 pF Cob and low V_BE(sat) support clean transient response in audio and RF detector applications, but it is not rated for GHz-range operation.

How does BC558B_J18Z handle thermal stress in continuous operation?

BC558B_J18Z has a thermal resistance R_JA of 250 °C/W on standard FR-4 PCBs. At 25°C ambient, its 500 mW power dissipation limit drops by 4.0 mW per °C rise-so at 75°C ambient, maximum safe dissipation is 300 mW. Layouts must provide adequate copper area and avoid enclosure hotspots to prevent junction temperatures exceeding 150°C.