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

NXP Semiconductors BC557C,126

Name: BC557C,126
Brand: NXP Semiconductors
SKU: BC557C,126
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC557C,126

Manufacturer:: NXP Semiconductors

Category:: Single Bipolar Transistors

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

Datasheet:: BC557C,126.pdf

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

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BC557C,126 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 DC current gain h_FE of 420–800 at I_C = −2 mA, used in low-voltage signal switching and linear amplification circuits.

For engineers reviewing the BC557C,126 datasheet, BC557C,126 pinout, BC557C,126 application, or BC557C,126 equivalent, key selection criteria include guaranteed h_FE range, V_CEO derating above 25 °C, thermal resistance R_th(j-a) = 250 K/W on FR4, and compatibility with BC547 NPN complement in push-pull stages.

Technical Context

The BC557C,126 operates as a silicon PNP BJT with base-controlled current amplification, optimized for linear and saturated switching modes. Its h_FE binning (420–800) ensures consistent gain in bias-stable amplifier designs, while V_CEsat ≤ −300 mV at I_C = −10 mA / I_B = −0.5 mA supports low-loss switching in 5 V and 3.3 V logic interfaces.

Thermal performance is defined for mounting on standard FR4 PCBs without heatsink; junction temperature must remain ≤150 °C under continuous operation. Cut-off leakage (I_CBO ≤ −15 nA at 25 °C) and noise figure (2–10 dB at 1 kHz) confirm suitability for low-noise preamplifier and sensor interface roles.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−45 V - Maximum collector-emitter voltage before breakdown; sets upper rail limit for 3.3 V/5 V supply circuits.
h_FE	420–800 - Guaranteed DC current gain at I_C = −2 mA, V_CE = −5 V; enables predictable biasing in Class-A amplifiers.
V_CEsat	−60 to −300 mV - Saturation voltage at I_C = −10 mA / I_B = −0.5 mA; determines power loss and logic-level compatibility in switch mode.
P_tot	500 mW - Total power dissipation at T_amb ≤ 25 °C; requires thermal derating above ambient for sustained operation.
R_th(j-a)	250 K/W - Junction-to-ambient thermal resistance on FR4 board; defines temperature rise per watt of dissipated power.
f_T	100 MHz - Transition frequency at V_CE = −5 V, I_C = −10 mA; indicates usable bandwidth for audio and low-speed digital signal amplification.

Pinout & Package

BC557C,126 is housed in a plastic single-ended leaded through-hole package (TO-92 / SOT54 / SC-43A), with 3 leads and standard 2.54 mm lead pitch. The package is compatible with wave soldering and manual prototyping.

Pin/Terminal	Circuit Role	Design Meaning
1	Emitter	Current exit terminal; connected to most positive rail in PNP common-emitter configurations.
2	Base	Control terminal; requires negative bias relative to emitter to enable conduction.
3	Collector	Current entry terminal; typically tied to load and supply rail in switching applications.

Key Features

Feature	Design Value
Guaranteed h_FE bin	420–800 at I_C = −2 mA - Ensures stable bias point across production lots in amplifier feedback networks.
Low V_CEsat	≤ −300 mV at I_C = −10 mA - Minimizes voltage drop and power loss in saturated switching applications.
Low leakage	I_CBO ≤ −15 nA at 25 °C - Supports high-impedance input stages and battery-powered standby circuits.
Standard TO-92 footprint	Compatible with legacy PCB layouts and hand-soldering workflows - eliminates redesign when replacing BC557 variants.

Applications

Audio Pre-amplifier Stage	Logic-Level Inverter
Use Scenario: Amplifying weak microphone or sensor signals in portable audio devices operating from 3.3 V or 5 V supplies. IC Role / Device Role / Timing Role: PNP BJT configured in common-emitter topology to provide voltage gain and impedance transformation. Use Value: High h_FE (420–800) and low noise figure (2–10 dB) preserve signal integrity in first-stage amplification.	Use Scenario: Converting TTL/CMOS logic HIGH to LOW output in microcontroller peripheral interfacing. IC Role / Device Role / Timing Role: Saturated PNP switch driving LED indicators or pull-up loads with active-low control. Use Value: V_CEsat ≤ −300 mV ensures minimal voltage overhead and full rail-to-rail output swing.
Current Mirror Reference	Discrete Voltage Regulator
Use Scenario: Building matched current sources in analog IC test fixtures or precision instrumentation front-ends. IC Role / Device Role / Timing Role: One half of a discrete PNP current mirror pair, biased with fixed base voltage. Use Value: Tight h_FE tolerance and low I_CBO support accurate current replication over temperature.	Use Scenario: Regulating output voltage in low-power linear supplies where IC regulators are unavailable or oversized. IC Role / Device Role / Timing Role: Pass transistor controlled by Zener-biased base reference network. Use Value: V_CEO = −45 V and P_tot = 500 mW allow safe operation up to 30 V input with moderate load current.

Audio Pre-amplifier Stage

Logic-Level Inverter

Use Scenario: Amplifying weak microphone or sensor signals in portable audio devices operating from 3.3 V or 5 V supplies.

IC Role / Device Role / Timing Role: PNP BJT configured in common-emitter topology to provide voltage gain and impedance transformation.

Use Value: High h_FE (420–800) and low noise figure (2–10 dB) preserve signal integrity in first-stage amplification.

Use Scenario: Converting TTL/CMOS logic HIGH to LOW output in microcontroller peripheral interfacing.

IC Role / Device Role / Timing Role: Saturated PNP switch driving LED indicators or pull-up loads with active-low control.

Use Value: V_CEsat ≤ −300 mV ensures minimal voltage overhead and full rail-to-rail output swing.

Current Mirror Reference

Discrete Voltage Regulator

Use Scenario: Building matched current sources in analog IC test fixtures or precision instrumentation front-ends.

IC Role / Device Role / Timing Role: One half of a discrete PNP current mirror pair, biased with fixed base voltage.

Use Value: Tight h_FE tolerance and low I_CBO support accurate current replication over temperature.

Use Scenario: Regulating output voltage in low-power linear supplies where IC regulators are unavailable or oversized.

IC Role / Device Role / Timing Role: Pass transistor controlled by Zener-biased base reference network.

Use Value: V_CEO = −45 V and P_tot = 500 mW allow safe operation up to 30 V input with moderate load current.

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,126	h_FE = 220–475 (lower gain range); same V_CEO, V_CEsat, and package.	Suitable where lower gain reduces risk of oscillation in high-frequency feedback loops.	Select BC557B,126 when circuit stability outweighs gain requirement, especially in RF-adjacent analog stages.
BC558,126	V_CEO = −30 V (reduced breakdown rating); otherwise identical pinout, h_FE, and thermal specs.	Limited to sub-24 V systems; not recommended for 5 V rail-swing margin-critical designs.	Choose BC558,126 only in cost-sensitive, low-voltage (<20 V) applications where V_CEO margin is verified.

Compared with BC557B,126 and BC558,126, the BC557C,126 delivers highest guaranteed h_FE for precision biasing, maintains widest V_CEO margin among BC557-series variants, and retains full compatibility with existing TO-92 footprints and drive networks.

Availability

BC557C,126 is available at Aetrix Electronics and suitable for audio pre-amplifiers, logic-level inverters, current mirror references, and discrete voltage regulators requiring stable component supply and long-term obsolescence management.

Supply support for BC557C,126 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 BC557C,126 belongs to NXP's legacy general-purpose transistor product line, designed for cost-effective, reliable discrete amplification and switching in mass-produced consumer and industrial electronics.

FAQ

What is the maximum collector-emitter voltage rating for BC557C,126?

The BC557C,126 has a maximum collector-emitter voltage (V_CEO) rating of −45 V under open-base conditions. This rating applies at T_amb ≤ 25 °C and must be derated linearly with increasing ambient temperature per the device's thermal characteristics. Exceeding this voltage risks irreversible breakdown of the BC557C,126 junction.

What is the guaranteed DC current gain (h_FE) range for BC557C,126?

The BC557C,126 is binned to guarantee a DC current gain (h_FE) between 420 and 800 when measured at I_C = −2 mA and V_CE = −5 V. This high-gain bin distinguishes it from BC557A and BC557B variants and supports stable biasing in low-current amplifier stages using the BC557C,126.

Can BC557C,126 be used as a direct replacement for BC557B,126?

Yes, the BC557C,126 is pin-compatible and electrically substitutable for BC557B,126 in most circuits, but its higher h_FE range (420–800 vs. 220–475) may increase gain or instability in marginal feedback designs. Verify loop stability and saturation margins when upgrading to BC557C,126 in an existing BC557B,126 design.

What is the thermal resistance (R_th(j-a)) of BC557C,126 on a standard PCB?

The BC557C,126 has a junction-to-ambient thermal resistance (R_th(j-a)) of 250 K/W when mounted on a standard FR4 printed-circuit board without heatsinking. This value assumes natural convection cooling and defines the temperature rise per watt of dissipated power - critical for calculating safe operating area in continuous-duty BC557C,126 applications.

Does BC557C,126 have a specified transition frequency (f_T)?

Yes, the BC557C,126 has a minimum transition frequency (f_T) of 100 MHz, measured at V_CE = −5 V and I_C = −10 mA. This f_T confirms the BC557C,126's capability for audio-frequency amplification and low-speed digital signal conditioning, though it is not intended for RF or GHz-range operation.

BC557C,126 Specifications

Product attributes: Attribute value

Manufacturer:: NXP Semiconductors

Series:: -

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

Packaging:: Tape & Box (TB)

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:: 420 @ 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

BC557C,126 FAQ

1.How can I place an order for BC557C,126 through Aetrix?

Please submit a Request for Quotation (RFQ) for BC557C,126 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 BC557C,126 reliable?

The price and inventory of BC557C,126 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC557C,126 is usually 5 days.

3.What payment methods are accepted for BC557C,126?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC557C,126 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC557C,126?

BC557C,126 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC557C,126 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 BC557C,126?

For technical support, including BC557C,126 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC557C,126 requirements.

6.How does Aetrix verify that BC557C,126 is sourced from the original manufacturer or authorized distributors?

All BC557C,126 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 BC557C,126 meets industry standards.

7.What is the process for return or replacement of BC557C,126?

All BC557C,126 units undergo pre-shipment inspection (PSI). If there is an issue with BC557C,126, 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 BC557C,126 part is unused and in its original packaging.

Return procedure for BC557C,126:

1.Submit a request within 90 days.

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

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