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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

NXP Semiconductors BC557,112

Name: BC557,112
Brand: NXP Semiconductors
SKU: BC557,112
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC557,112

Manufacturer:: NXP Semiconductors

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Datasheet:: BC557,112.pdf

Description:: TRANS PNP 45V 0.1A TO-92-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BC557,112 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, commonly used in low-voltage switching and small-signal amplification circuits such as LED drivers and audio preamplifiers.

For engineers reviewing the BC557,112 datasheet, BC557,112 pinout, BC557,112 application, or BC557,112 equivalent, key selection criteria include its −45 V collector-emitter breakdown voltage, h_FE range of 125–800 at −2 mA, V_CEsat ≤ −300 mV at −10 mA/−0.5 mA drive, and compatibility with BC547 NPN complement in dual-transistor designs.

Technical Context

The BC557,112 operates as a silicon PNP BJT with fixed emitter-base and collector-base junctions optimized for linear amplification and saturated switching below 100 mA DC. Its thermal resistance R_th(j-a) is 250 K/W on FR4 PCB, and base-emitter voltage V_BE is −650 mV typical at −2 mA and −5 V V_CE.

It exhibits f_T = 100 MHz at −5 V V_CE and −10 mA I_C, with noise figure of 2–10 dB at 1 kHz under 2 kΩ source impedance - confirming suitability for low-noise analog front-ends where gain stability and low distortion are required.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−45 V: Maximum safe collector-emitter voltage before avalanche breakdown in open-base configuration.
I_C	−100 mA: Continuous DC collector current limit; defines maximum load-handling capability in switching applications.
h_FE	125–800: DC current gain range at −2 mA I_C, −5 V V_CE; enables predictable biasing across production lots.
V_CEsat	−60 to −650 mV: Saturation voltage span across I_C = −10 mA to −100 mA; determines conduction loss and heat generation in switch mode.
f_T	100 MHz: Transition frequency at −5 V V_CE, −10 mA I_C; sets upper usable bandwidth for small-signal amplification.
R_th(j-a)	250 K/W: Junction-to-ambient thermal resistance on standard FR4 board; governs temperature rise under 500 mW dissipation.

Pinout & Package

BC557,112 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.

Pin/Terminal	Circuit Role	Design Meaning
1	Emitter	Current exit terminal in PNP operation; connected to most positive rail in common-emitter switch configurations.
2	Base	Control terminal; requires negative current relative to emitter to forward-bias BE junction and enable conduction.
3	Collector	Current entry terminal; tied to load and supply rail in switching topologies; reverse-biased during cutoff.

Key Features

Feature	Design Value
Low-voltage PNP architecture	Rated for −45 V V_CEO, enabling use in 24 V and lower DC systems without derating.
Wide h_FE spread (125–800)	Supports both high-gain amplification (e.g., microphone preamps) and robust switching (e.g., relay drivers) within same family.
Low saturation voltage	V_CEsat ≤ −300 mV at −10 mA ensures minimal power loss and self-heating in digital logic interface circuits.
100 MHz f_T	Permits stable small-signal amplification up to audio and low-RF frequencies without external compensation.

Applications

LED Driver Circuit	Audio Pre-amplifier Stage
Use Scenario: Driving discrete LEDs from microcontroller GPIO pins with current limiting via base resistor. IC Role / Device Role / Timing Role: PNP switch controlling current flow from V_CC through LED to ground. Use Value: Low V_CEsat minimizes voltage drop across transistor, preserving forward voltage margin for LED brightness control.	Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors in portable audio devices. IC Role / Device Role / Timing Role: Common-emitter small-signal amplifier providing 20–40 dB voltage gain. Use Value: High h_FE and low noise figure (2–10 dB) maintain signal integrity while reducing component count vs. op-amp solutions.
Relay Control Interface	Level Translation Circuit
Use Scenario: Isolating and driving 5–12 V coil relays from 3.3 V or 5 V logic outputs. IC Role / Device Role / Timing Role: Saturated PNP switch sinking relay coil current when base is pulled low. Use Value: −100 mA I_C rating supports typical relay coils (≤70 mA), and −45 V V_CEO accommodates inductive kickback suppression.	Use Scenario: Converting logic-high-active signals from 3.3 V MCU to active-low-enable inputs on legacy 5 V peripherals. IC Role / Device Role / Timing Role: Inverting level shifter using emitter-follower or common-emitter topology. Use Value: Predictable V_BE ≈ −650 mV and tight V_CEsat tolerance ensure consistent output thresholds across temperature and supply variation.

LED Driver Circuit

Audio Pre-amplifier Stage

Use Scenario: Driving discrete LEDs from microcontroller GPIO pins with current limiting via base resistor.

IC Role / Device Role / Timing Role: PNP switch controlling current flow from V_CC through LED to ground.

Use Value: Low V_CEsat minimizes voltage drop across transistor, preserving forward voltage margin for LED brightness control.

Use Scenario: Amplifying weak signals from electret microphones or piezoelectric sensors in portable audio devices.

IC Role / Device Role / Timing Role: Common-emitter small-signal amplifier providing 20–40 dB voltage gain.

Use Value: High h_FE and low noise figure (2–10 dB) maintain signal integrity while reducing component count vs. op-amp solutions.

Relay Control Interface

Level Translation Circuit

Use Scenario: Isolating and driving 5–12 V coil relays from 3.3 V or 5 V logic outputs.

IC Role / Device Role / Timing Role: Saturated PNP switch sinking relay coil current when base is pulled low.

Use Value: −100 mA I_C rating supports typical relay coils (≤70 mA), and −45 V V_CEO accommodates inductive kickback suppression.

Use Scenario: Converting logic-high-active signals from 3.3 V MCU to active-low-enable inputs on legacy 5 V peripherals.

IC Role / Device Role / Timing Role: Inverting level shifter using emitter-follower or common-emitter topology.

Use Value: Predictable V_BE ≈ −650 mV and tight V_CEsat tolerance ensure consistent output thresholds across temperature and supply variation.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC557B,112	Higher h_FE bin (220–475) vs. BC557,112's full 125–800 range; otherwise identical ratings and pinout.	Better suited for high-gain linear amplification where consistent minimum gain >220 is required.	Select BC557B,112 when guaranteed minimum h_FE matters more than cost-sensitive broad-range flexibility.
MMBT557LT1G	SOT-23 surface-mount package; same −45 V V_CEO, −100 mA I_C, but lower P_tot (310 mW) and higher R_th(j-a) (400 K/W).	Requires PCB redesign for SMT assembly; not suitable for through-hole prototyping or high-power dissipation.	Choose MMBT557LT1G only for space-constrained, automated production where footprint reduction outweighs thermal and layout trade-offs.

Compared with BC557,112, BC557B,112 offers tighter h_FE assurance for precision biasing, while MMBT557LT1G sacrifices thermal performance and through-hole compatibility for miniaturization - making BC557,112 optimal for general-purpose through-hole designs requiring balance of gain flexibility, ruggedness, and ease of hand-soldering.

Availability

BC557,112 is available at Aetrix Electronics and suitable for LED driver circuits, audio pre-amplifier stages, and relay control interfaces requiring stable component supply and long-term obsolescence management.

Supply support for BC557,112 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 BC557,112 belongs to NXP's legacy general-purpose transistor product line, designed specifically for cost-sensitive, high-volume analog and mixed-signal applications where reliability, consistency, and wide parametric spread are prioritized over ultra-high-speed or RF performance.

FAQ

What is the maximum collector-emitter voltage rating for BC557,112?

The BC557,112 has a maximum collector-emitter voltage (V_CEO) rating of −45 V under open-base conditions. This value is specified in the Absolute Maximum Ratings table of the official NXP datasheet and defines the upper limit for safe DC operation without risk of junction breakdown. Exceeding −45 V may cause irreversible damage to the BC557,112, especially during inductive load switching events.

Does BC557,112 have a specified transition frequency (f_T)?

Yes, the BC557,112 has a specified transition frequency (f_T) of 100 MHz, measured at −5 V V_CE and −10 mA I_C. This parameter confirms the BC557,112's capability for small-signal amplification up to low-RF frequencies and distinguishes it from slower general-purpose transistors. The f_T value is documented in the Characteristics section of the NXP product data sheet.

What is the typical base-emitter voltage (V_BE) of BC557,112 at −2 mA collector current?

The typical base-emitter voltage (V_BE) of BC557,112 is −650 mV when operated at −2 mA collector current and −5 V V_CE, as stated in the NXP datasheet's Characteristics table. This value is critical for accurate bias network design and remains stable across ambient temperatures due to the documented −2 mV/K temperature coefficient.

Is BC557,112 pin-compatible with BC556,112?

No, BC557,112 is not pin-compatible with BC556,112 in terms of electrical specifications, though both share the same TO-92 (SOT54) physical package and pinout. The BC556,112 is rated for −65 V V_CEO and −80 V V_CBO, whereas BC557,112 is limited to −45 V V_CEO and −50 V V_CBO. Substituting BC557,112 for BC556,112 in high-voltage circuits risks premature failure.

What is the thermal resistance from junction to ambient (R_th(j-a)) for BC557,112?

The thermal resistance from junction to ambient (R_th(j-a)) for BC557,112 is 250 K/W when mounted on a standard FR4 printed-circuit board, as specified in the Thermal Characteristics section of the NXP datasheet. This value directly determines temperature rise: at 500 mW dissipation, junction temperature rises ~125 °C above ambient, requiring careful thermal design in enclosed or high-temperature environments.

BC557,112 Specifications

Product attributes: Attribute value

Manufacturer:: NXP Semiconductors

Series:: -

Package/Case:: TO-226-3, TO-92-3 (TO-226AA) Formed Leads

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 100 mA

Voltage - Collector Emitter Breakdown (Max):: 45 V

Vce Saturation (Max) @ Ib, Ic:: 650mV @ 5mA, 100mA

Current - Collector Cutoff (Max):: 15nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 125 @ 2mA, 5V

Power - Max:: 500 mW

Frequency - Transition:: 100MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

BC557,112 FAQ

1.How can I place an order for BC557,112 through Aetrix?

Please submit a Request for Quotation (RFQ) for BC557,112 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for BC557,112 reliable?

The price and inventory of BC557,112 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC557,112 is usually 5 days.

3.What payment methods are accepted for BC557,112?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC557,112 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC557,112?

BC557,112 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC557,112 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for BC557,112?

For technical support, including BC557,112 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC557,112 requirements.

6.How does Aetrix verify that BC557,112 is sourced from the original manufacturer or authorized distributors?

All BC557,112 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BC557,112 meets industry standards.

7.What is the process for return or replacement of BC557,112?

All BC557,112 units undergo pre-shipment inspection (PSI). If there is an issue with BC557,112, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The BC557,112 part is unused and in its original packaging.

Return procedure for BC557,112:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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