onsemi BC556

Overview

BC556 from onsemi is a PNP epitaxial silicon transistor designed for general-purpose switching and linear amplification in low-to-medium power circuits, featuring −65 V collector-emitter breakdown voltage (V_CEO), −100 mA DC collector current rating, and 110–800 DC current gain (h_FE) at −2 mA collector current. It operates reliably across −65°C to +150°C and is commonly used in discrete amplifier stages, level-shifting interfaces, and relay drivers.

For engineers reviewing the BC556 datasheet, pinout, applications, or equivalent options, key selection considerations include its high-voltage PNP capability, TO-92 package compatibility, thermal dissipation limit of 500 mW at 25°C, and complementary pairing with BC546–BC550 NPN devices in push-pull configurations.

Technical Context

The BC556 functions as a medium-gain, high-voltage PNP bipolar junction transistor optimized for DC-coupled amplification and saturated switching. Its −65 V V_CEO rating enables use in higher-rail negative supply rails, while its 150 MHz f_T supports audio-frequency and low-speed digital signal handling.

Thermal performance is defined by a 250°C/W junction-to-ambient thermal resistance (R_JA) on standard FR-4 PCBs, and its −5 V V_EBO rating limits base-emitter reverse bias tolerance. The device exhibits low leakage (ICBO ≤ −15 nA at −30 V V_CB) and predictable saturation behavior (V_CE(sat) = −90 mV typical at −10 mA/−0.5 mA drive).

Key Specifications

Pinout & Package

BC556 is housed in a TO-92-3 plastic package (case 135AR or 135AN), with standardized lead configuration: Pin 1 = Collector, Pin 2 = Base, Pin 3 = Emitter. The package is RoHS-compliant, Pb-free, and halogen-free.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC557 and BC856, the BC556 uniquely balances high-voltage capability, through-hole serviceability, and broad h_FE binning-making it preferred for prototyping, industrial controls, and legacy system replacements where −65 V margin and manual assembly coexist.

Availability

BC556 is available at Aetrix Electronics and suitable for audio preamplifiers, relay driver circuits, and level-shifting interfaces requiring stable component supply across extended product lifecycles.

Supply support for BC556 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, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC556 belongs to onsemi's legacy general-purpose bipolar transistor family, engineered for reliability and consistency in discrete analog signal conditioning and power control applications across decades of industrial deployment.

FAQ

What is the maximum collector-emitter voltage rating for BC556?

The BC556 has a guaranteed minimum collector-emitter breakdown voltage (V_CEO) of −65 V at 25°C. This rating allows safe operation in negative-rail circuits up to −65 V, with derating required above 25°C ambient per the device's thermal characteristics. The BC556 datasheet confirms this value under Absolute Maximum Ratings, and it distinguishes the BC556 from lower-voltage variants like BC557 (−45 V) and BC558 (−30 V).

Is BC556 pin-compatible with BC546–BC550 NPN transistors?

No-BC556 is a PNP transistor while BC546–BC550 are NPN devices, so their polarity and biasing requirements differ fundamentally. However, BC556 is electrically complementary: it shares identical TO-92 package dimensions, pinout (C-B-E), and mechanical footprint with those NPN parts, enabling direct placement in mirrored circuit positions such as push-pull output stages or differential pairs without PCB redesign.

What is the typical DC current gain (h_FE) of BC556 at 2 mA collector current?

The BC556 exhibits a DC current gain (h_FE) ranging from 110 to 800 at V_CE = −5 V and I_C = −2 mA, depending on the h_FE classification bin (A/B/C). This wide gain spread is intentional and documented in the Electrical Characteristics table; design margins should accommodate the full min–max range unless bin-specific parts (e.g., BC556B) are procured.

Can BC556 be used in low-noise audio amplifier designs?

Yes-the BC556 is specified with a noise figure of 2–10 dB at 1 kHz (V_CE = −5 V, I_C = −200 µA, R_G = 2 kΩ), shared with BC557 and BC558. While not as low-noise as BC559/BC560 (1–4 dB), this performance is adequate for non-critical preamp stages, tone controls, or line drivers where cost and availability outweigh ultra-low-noise requirements.

What package options are available for BC556?

The BC556 is offered in two TO-92 variants: case 135AR (lead-formed, for tape-and-reel or fan-fold packaging) and case 135AN (straight-lead, bulk-packed). Both share identical electrical specifications, pinout (C-B-E), and thermal characteristics. The choice depends on assembly method-135AR suits automated pick-and-place, while 135AN facilitates hand soldering and breadboarding.