onsemi BC558BTA

Overview

BC558BTA from ON Semiconductor is a PNP epitaxial silicon transistor in TO-92 package, rated for V_CEO = −30 V, I_C = −100 mA, and h_FE = 200–450 (Class B), with V_BE(on) = −600 to −750 mV at I_C = −2 mA and f_T = 150 MHz - used in low-noise audio preamplifiers and discrete switching stages in industrial control interfaces.

For engineers reviewing the BC558BTA datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, TO-92 terminal mapping, real-world use cases in signal conditioning and level translation, and two validated alternative parts with documented h_FE and voltage rating differences.

Technical Context

This device operates as a general-purpose PNP bipolar junction transistor optimized for linear amplification and saturated switching. Its −30 V V_CEO and −5 V V_EBO support moderate-voltage biasing in dual-supply analog circuits, while its 150 MHz f_T enables stable gain up to audio frequencies. The 6 pF Cob ensures minimal Miller effect in common-emitter configurations.

Thermal performance is defined by R_θJA = 250 °C/W on standard FR-4 PCBs, with 500 mW total power dissipation derated at 4.0 mW/°C above 25 °C ambient. Noise figure is specified at 2–10 dB (1 kHz, 200 μA), confirming suitability for low-level signal amplification where BC559/BC560 variants offer lower noise.

Key Specifications

Pinout & Package

BC558BTA uses the industry-standard TO-92 3-lead plastic package with straight leads and ammo packing. Pin 1 is Collector, Pin 2 is Base, Pin 3 is Emitter - confirmed per JEDEC TO-92 mechanical drawing and Fairchild Rev. 1.7 datasheet Figure 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC558BTA, BC557BTA offers higher voltage tolerance without altering gain or package, while MMBT558LT1G trades power and thermal margin for miniaturization - making BC558BTA optimal for through-hole, medium-power, low-noise PNP roles where proven reliability and thermal headroom are prioritized.

Availability

BC558BTA is available at Aetrix Electronics and suitable for industrial control interfaces, audio signal conditioning, and discrete switching applications requiring stable component supply and long-term obsolescence management.

Supply support for BC558BTA 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 markets.

The BC558BTA belongs to the legacy BC556–BC560 PNP transistor family originally developed by Fairchild and now maintained by ON Semiconductor for general-purpose linear and switching applications in cost-sensitive, through-hole designs.

FAQ

What is the maximum collector-emitter voltage rating for BC558BTA?

The BC558BTA has a V_CEO rating of −30 V, meaning it can safely withstand up to 30 volts between collector and emitter with the base open. This value is confirmed in the Absolute Maximum Ratings table of the Fairchild/ON Semiconductor datasheet Rev. 1.7 and applies strictly to the BC558 and BC559 variants - not the higher-rated BC556 or BC557. Exceeding −30 V risks avalanche breakdown and permanent damage to the BC558BTA.

Does BC558BTA have a specified noise figure, and how does it compare to BC559BTA?

Yes, BC558BTA has a noise figure of 2–10 dB at 1 kHz, 200 μA collector current, and 2 kΩ source resistance. In contrast, BC559BTA is explicitly characterized for low-noise operation with a tighter 1.2–4.0 dB range under identical conditions. The BC558BTA's higher noise floor makes it appropriate for general amplification, while BC559BTA is preferred for ultra-low-noise front-end stages - both are valid choices depending on signal integrity requirements in the final BC558BTA design.

What is the h_FE range for BC558BTA, and how is it binned?

The BC558BTA is classified as "Class B" with a guaranteed h_FE range of 200 to 450 when measured at V_CE = −5 V and I_C = −2 mA. This binning is performed during final test and marked as "BC558B" on the device body. It distinguishes BC558BTA from BC558ATA (110–220) and BC558CTA (420–800), ensuring consistent gain behavior across production lots of the BC558BTA.

Can BC558BTA be used as a direct replacement for BC557BTA in an existing circuit?

No - BC558BTA is not a direct replacement for BC557BTA due to its lower V_CEO rating (−30 V vs. −45 V). While both share identical TO-92 packaging, pinout, and h_FE Class B grading, substituting BC558BTA into a circuit designed for −45 V operation risks premature breakdown. The BC558BTA may function temporarily at lower voltages, but long-term reliability of BC558BTA cannot be assured beyond −30 V - always verify operating V_CE margins before interchanging.

What is the thermal resistance and power derating behavior of BC558BTA?

BC558BTA has a junction-to-ambient thermal resistance (R_θJA) of 250 °C/W on a standard FR-4 PCB (76 mm × 114 mm), with a maximum power dissipation of 500 mW at 25 °C ambient. Power must be linearly derated by 4.0 mW/°C above 25 °C - for example, at 75 °C ambient, max power drops to 300 mW. This thermal profile directly impacts safe continuous current in BC558BTA switching applications and must be modeled alongside V_CE(sat) and I_C.