NXP Semiconductors BC557B,112

Overview

BC557B,112 from NXP Semiconductors is a PNP general-purpose bipolar junction transistor in TO-92 (SOT54) package, rated for −45 V V_CEO, −100 mA I_C, and 500 mW P_tot, with h_FE of 220–475 at I_C = −2 mA, used in low-voltage signal switching and linear amplification circuits.

For engineers reviewing the BC557B,112 datasheet, BC557B,112 pinout, BC557B,112 application, or BC557B,112 equivalent, key selection criteria include its PNP polarity, TO-92 through-hole mounting, guaranteed DC current gain range, saturation voltage performance at defined drive conditions, and thermal resistance of 250 K/W on FR4 PCB.

Technical Context

The BC557B,112 operates as a standard PNP BJT with base-controlled current amplification, requiring reverse-biased emitter-base and collector-base junctions for active-region operation. Its design supports both switching (via overdrive into saturation) and analog amplification (with bias networks ensuring stable Q-point under temperature variation).

It exhibits V_BE ≈ −650 mV at I_C = −2 mA and V_CE = −5 V, with V_CEsat ≤ −300 mV at I_C = −10 mA / I_B = −0.5 mA, and f_T = 100 MHz - confirming suitability for audio-frequency and low-speed digital applications up to ~10 MHz switching.

Key Specifications

Pinout & Package

BC557B,112 is housed in a plastic single-ended leaded (through-hole) TO-92 package, also designated SOT54 or SC-43A, with 3 leads and standardized mechanical dimensions per IEC outline.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC557C,112 and PN2907A, the BC557B,112 offers balanced gain consistency and proven manufacturability for cost-sensitive consumer and industrial signal conditioning, avoiding over-specification while maintaining robustness at −45 V and −100 mA.

Availability

BC557B,112 is available at Aetrix Electronics and suitable for audio pre-amplifiers, LED driver switches, relay interfaces, and level-shifting circuits requiring stable component supply and long-term obsolescence management.

Supply support for BC557B,112 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

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and consumer applications.

The BC557B,112 belongs to NXP's legacy discrete transistor family designed for cost-effective, high-reliability general-purpose analog and switching functions in through-hole assembled electronics.

FAQ

What is the maximum collector-emitter voltage rating for BC557B,112?

The BC557B,112 has a maximum collector-emitter voltage (V_CEO) rating of −45 V under open-base conditions, as specified in the Absolute Maximum Ratings table of the NXP product data sheet dated 2004 Oct 11. This value defines the upper limit for safe DC operation without risk of avalanche breakdown. Exceeding this voltage, even briefly, may cause permanent device failure. The BC557B,112 must be operated within this limit in all circuit configurations.

What is the guaranteed DC current gain (h_FE) range for BC557B,112?

The BC557B,112 guarantees a DC current gain (h_FE) range of 220 to 475 when tested at I_C = −2 mA and V_CE = −5 V, per the Characteristics section of the official NXP datasheet. This range is distinct from BC557A (125–250) and BC557C (420–800). Designers must use the minimum h_FE of 220 for worst-case bias calculations in the BC557B,112.

Which package type does BC557B,112 use, and what are its key mechanical identifiers?

The BC557B,112 uses the TO-92 plastic single-ended leaded package, also known as SOT54 or SC-43A. Key mechanical identifiers include 3 leads, 2.54 mm lead pitch (e), 1.27 mm inner lead pitch (e1), overall length of 14.5 mm (L), and body width of 4.8 mm (D). These dimensions are standardized per IEC and JEDEC outlines and ensure compatibility with automated insertion and hand-soldering tooling.

Can BC557B,112 be used as a direct replacement for BC557 in existing designs?

Yes - BC557B,112 is a specific gain-bin variant of the BC557 family and shares identical absolute maximum ratings, pinout, package, and electrical test conditions with other BC557 suffixes. It is fully interchangeable in terms of physical fit and voltage/current capability. However, because its h_FE range (220–475) differs from BC557A (125–250) or BC557C (420–800), circuit biasing may require verification if gain sensitivity is critical in the BC557B,112 application.

What is the thermal resistance (R_th(j-a)) of BC557B,112, and how is it measured?

The BC557B,112 has a junction-to-ambient thermal resistance (R_th(j-a)) of 250 K/W, measured with the device mounted on a standard FR4 printed-circuit board per the NXP thermal characterization note. This value assumes no additional heatsinking and defines the temperature rise (in Kelvin) per milliwatt of power dissipated. At its 500 mW maximum power rating, the junction will rise approximately 125 °C above ambient - necessitating ambient derating above 25 °C for continuous operation.