onsemi BC558_D81Z

Overview

BC558_D81Z from onsemi is a PNP epitaxial silicon transistor designed for general-purpose switching and linear amplification in low-power analog and digital circuits. It features V_CEO = −30 V, I_C = −100 mA, h_FE = 110–800 (Class B), f_T = 150 MHz, and V_BE(on) ≈ −660 mV at I_C = −2 mA - enabling reliable operation in bias networks, signal inversion stages, and discrete logic interfaces.

For engineers reviewing the BC558_D81Z datasheet, pinout, applications, or equivalent options, key selection criteria include its TO-92-3 package compatibility, PNP polarity with defined saturation voltage limits, low-noise capability (NF = 2–10 dB), and complementarity to BC546–BC550 NPN series in push-pull configurations.

Technical Context

The BC558_D81Z operates as a medium-gain, medium-speed PNP bipolar junction transistor optimized for DC-coupled amplification and saturated switching. Its h_FE classification (B-grade) ensures predictable current gain between 200–450 at I_C = −2 mA and V_CE = −5 V, while f_T = 150 MHz supports audio-frequency and low-MHz signal handling without significant phase distortion.

Thermal design is constrained by R_JA = 250 °C/W and P_D = 500 mW at T_A = 25 °C, with linear derating of 4.0 mW/°C above ambient. The device's V_CEO = −30 V and V_CBO = −30 V define safe operating limits for low-voltage negative-rail applications such as battery-powered sensor interfaces and level-shifting circuits.

Key Specifications

Pinout & Package

BC558_D81Z is housed in a TO-92-3 plastic package (Case 135AR), with standard leadform orientation: flat side facing viewer, leads downward, left-to-right pin order as Collector–Base–Emitter.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC558_D81Z, BC557BTA offers higher voltage headroom without trade-offs in speed or noise, while BC559BTA sacrifices voltage margin and switching consistency for superior noise performance - making BC558_D81Z the balanced choice for cost-sensitive, dual-role (switching + amplification) designs.

Availability

BC558_D81Z is available at Aetrix Electronics and suitable for audio preamplifiers, discrete logic inverters, level-shifting interfaces, and battery-powered sensor bias networks requiring stable component supply and long-term obsolescence resilience.

Supply support for BC558_D81Z 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 delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The BC558_D81Z belongs to the BC55x PNP transistor family, engineered for robust, low-cost, general-purpose analog and digital signal control in space-constrained through-hole designs.

FAQ

What is the maximum collector-emitter voltage rating for BC558_D81Z?

The BC558_D81Z has a maximum collector-emitter voltage (V_CEO) rating of −30 V under standard test conditions (T_A = 25 °C). This rating defines the highest reverse voltage the transistor can withstand in common-emitter configuration before risking breakdown. Exceeding this value may cause irreversible damage or degraded reliability. Always observe derating curves for elevated ambient temperatures.

Is BC558_D81Z RoHS compliant and lead-free?

Yes, BC558_D81Z is RoHS compliant and manufactured as Pb-free, halogen-free, and BFR-free per onsemi's official datasheet revision 3 (June 2024). It meets EU Directive 2011/65/EU requirements and carries no hazardous substance exemptions - making it suitable for environmentally regulated commercial and industrial end products.

What package type does BC558_D81Z use, and what are its mechanical dimensions?

BC558_D81Z uses the TO-92-3 plastic package (Case 135AR), with nominal dimensions of 4.83 mm × 4.76 mm. The leadform is bent (lead-formed), and pin 1 is Collector, pin 2 is Base, pin 3 is Emitter when viewed with flat side facing and leads pointing downward. This matches industry-standard TO-92 footprints for manual or automated through-hole assembly.

How does the h_FE of BC558_D81Z compare to other BC55x variants?

BC558_D81Z is specified as Class B, with h_FE ranging from 200 to 450 at V_CE = −5 V and I_C = −2 mA. This sits between BC556/BC557 (Class A/B, up to 450) and BC559/BC560 (Class B/C, up to 800). Its gain band provides predictable biasing for amplification while retaining sufficient margin for switching saturation - distinguishing it from higher-gain, lower-voltage BC559 variants.

Can BC558_D81Z be used as a direct replacement for BC557 or BC559 in existing designs?

BC558_D81Z is pin-compatible and electrically similar to BC557 and BC559 in TO-92-3 packages, but substitution requires verification of voltage and noise requirements. BC557 supports higher V_CEO (−45 V); BC559 offers lower noise (1–4 dB). Using BC558_D81Z in place of BC557 may reduce voltage margin; replacing BC559 may increase system noise floor. Always validate in final circuit conditions.