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

onsemi BC557B

Name: BC557B
Brand: onsemi
SKU: BC557B
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC557B

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 Long Body

Datasheet:: BC557B.pdf

Description:: TRANS PNP 45V 0.1A TO92

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BC557B from onsemi is a general-purpose PNP silicon bipolar junction transistor (BJT) designed for linear amplification and switching applications in low-power analog and digital circuits. It features a DC current gain (h_FE) of 120–420 at I_C = −10 mA, V_CE = −5 V; V_CEO = −45 V; P_D = 625 mW at T_A = 25°C; and f_T = 320 MHz - enabling use in audio preamplifiers, level shifters, and discrete logic interfaces.

For engineers reviewing the BC557B datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-92 package compatibility, guaranteed h_FE binning (B-series), −45 V V_CEO rating, thermal resistance (R_JA = 200°C/W), and suitability for low-noise small-signal amplification at I_C ≤ −100 mA.

Technical Context

The BC557B operates as a standard PNP BJT with fixed-emitter biasing topology, requiring external base current control to regulate collector current flow. Its h_FE variation across temperature (−55°C to +150°C) and collector current (−2 mA to −100 mA) is documented in Figures 1, 4, and 7 of the datasheet, supporting stable DC bias design in Class-A amplifiers and saturated switches.

Small-signal performance is defined by f_T = 320 MHz at I_C = −10 mA, V_CE = −5 V, and Cob = 3.0–6.0 pF at V_CB = −10 V, making it suitable for RF front-end stages up to ~100 MHz when operated within safe SOA limits and with proper neutralization.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−45 V - Maximum allowable collector-to-emitter voltage before breakdown; defines safe operating range in common-emitter amplifier or switch configurations.
h_FE (I_C = −10 mA)	120–420 - Guaranteed DC current gain range for B-series devices; enables predictable base drive sizing in switching and linear designs.
P_D @ T_A = 25°C	625 mW - Continuous power dissipation limit at ambient temperature; derates 5.0 mW/°C above 25°C for thermal management planning.
f_T	320 MHz - Transition frequency at specified bias; indicates usable bandwidth for small-signal amplification up to mid-VHF frequencies.
C_ob	3.0–6.0 pF - Output capacitance at V_CB = −10 V; impacts high-frequency gain roll-off and stability in tuned amplifier stages.
NF	2.0 dB @ I_C = −0.2 mA - Low noise figure at low collector current; supports high-SNR preamplifier stages in sensor signal conditioning.

Pinout & Package

BC557B is housed in a TO-92 (Case 29, Style 17) through-hole plastic package with standardized lead configuration and Pb-free plating (per BC557BZL1G marking). The device has three terminals: Collector (Pin 1), Base (Pin 2), Emitter (Pin 3), as confirmed in the datasheet's marking diagram and package outline (page 7).

Pin/Terminal	Circuit Role	Design Meaning
1 - Collector	Main current output terminal in PNP configuration	Connected to most positive supply rail in common-emitter setups; must remain ≤ −45 V relative to emitter to avoid avalanche.
2 - Base	Control input for minority-carrier injection	Receives negative base current to turn on; requires current-limiting resistor to prevent IBM exceedance (−200 mA peak).
3 - Emitter	Current source terminal and reference node	Typically tied to V_CC or bias network; provides return path for collector and base currents; V_EBO = −5.0 V max limits reverse-base bias.

Key Features

Feature	Design Value
Pb-free TO-92 packaging	Complies with RoHS Directive 2011/65/EU; supports lead-free reflow soldering per ON Semiconductor Soldering Manual.
B-series h_FE binning	Guaranteed 120–420 gain range at I_C = −10 mA ensures consistent bias point setting without individual device screening.
Low noise figure	2.0 dB at I_C = −0.2 mA enables high-fidelity audio and precision sensor amplification without added op-amp complexity.
High f_T / low C_ob ratio	320 MHz f_T with only 3–6 pF output capacitance supports wideband gain in compact discrete RF amplifier designs.
Extended junction temperature range	−55°C to +150°C operation allows deployment in automotive under-hood, industrial control, and outdoor embedded systems.

Applications

Audio Pre-amplifier Stage	Discrete Logic Level Shifter
Use Scenario: Amplifying weak microphone or piezoelectric sensor signals in battery-powered portable audio recorders. IC Role / Device Role / Timing Role: Small-signal PNP amplifier in common-emitter configuration with emitter degeneration for linearity. Use Value: 2.0 dB noise figure and 320 MHz f_T preserve signal integrity while enabling gain >100 with minimal external components.	Use Scenario: Translating 3.3 V microcontroller GPIO outputs to interface with 5 V or 12 V legacy logic or relay drivers. IC Role / Device Role / Timing Role: Saturated PNP switch with base resistor biasing, acting as active-low level translator. Use Value: V_CE(sat) ≤ −0.3 V at I_C/I_B = 10 ensures <0.3 V drop across collector-emitter, minimizing power loss and heat rise.
LED Driver Switch	Current Mirror Reference
Use Scenario: Driving indicator LEDs or low-current status lamps from MCU I/O pins with current limiting via base resistor. IC Role / Device Role / Timing Role: Digital switch operating in saturation region, controlled by microcontroller output. Use Value: I_C = −100 mA continuous rating and −200 mA peak support multiple LEDs or higher-brightness indicators reliably.	Use Scenario: Building matched current sources in analog sensor conditioning circuits or precision DAC output buffers. IC Role / Device Role / Timing Role: Active component in two-transistor current mirror topology with emitter resistors for thermal tracking. Use Value: Tight h_FE binning (B-series) and low V_BE(on) variation (−0.55 to −0.7 V) improve mirror accuracy and temperature stability.

Audio Pre-amplifier Stage

Discrete Logic Level Shifter

Use Scenario: Amplifying weak microphone or piezoelectric sensor signals in battery-powered portable audio recorders.

IC Role / Device Role / Timing Role: Small-signal PNP amplifier in common-emitter configuration with emitter degeneration for linearity.

Use Value: 2.0 dB noise figure and 320 MHz f_T preserve signal integrity while enabling gain >100 with minimal external components.

Use Scenario: Translating 3.3 V microcontroller GPIO outputs to interface with 5 V or 12 V legacy logic or relay drivers.

IC Role / Device Role / Timing Role: Saturated PNP switch with base resistor biasing, acting as active-low level translator.

Use Value: V_CE(sat) ≤ −0.3 V at I_C/I_B = 10 ensures <0.3 V drop across collector-emitter, minimizing power loss and heat rise.

LED Driver Switch

Current Mirror Reference

Use Scenario: Driving indicator LEDs or low-current status lamps from MCU I/O pins with current limiting via base resistor.

IC Role / Device Role / Timing Role: Digital switch operating in saturation region, controlled by microcontroller output.

Use Value: I_C = −100 mA continuous rating and −200 mA peak support multiple LEDs or higher-brightness indicators reliably.

Use Scenario: Building matched current sources in analog sensor conditioning circuits or precision DAC output buffers.

IC Role / Device Role / Timing Role: Active component in two-transistor current mirror topology with emitter resistors for thermal tracking.

Use Value: Tight h_FE binning (B-series) and low V_BE(on) variation (−0.55 to −0.7 V) improve mirror accuracy and temperature stability.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC557C	Higher h_FE range (180–500 at I_C = −10 mA); otherwise identical ratings and pinout.	Better suited for high-gain, low-base-drive applications like low-power oscillator feedback networks.	Select BC557C when tighter gain control or lower base current is required; BC557B remains optimal for moderate-gain, cost-sensitive designs.
PN2907A	V_CEO = −60 V, h_FE = 100–300, TO-92 package, same pinout (C-B-E), but higher R_JA (250°C/W).	Preferred where higher breakdown margin is needed, e.g., in 48 V telecom interface circuits with transient protection.	Choose PN2907A for enhanced voltage headroom; verify thermal design due to reduced power dissipation capability.

Compared with BC557C and PN2907A, the BC557B offers balanced h_FE, proven reliability in consumer audio and industrial controls, and optimal thermal performance (R_JA = 200°C/W) for space-constrained TO-92 layouts - making it the default choice for general-purpose PNP amplification and switching where gain consistency and manufacturability are prioritized.

Availability

BC557B is available at Aetrix Electronics and suitable for audio preamplifiers, discrete logic level shifters, and LED driver switches requiring stable component supply, long-term obsolescence management, and RoHS-compliant sourcing.

Supply support for BC557B 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 focused on energy-efficient innovation for automotive, industrial, cloud, medical, and IoT applications.

The BC557B belongs to onsemi's legacy general-purpose bipolar transistor family, engineered for cost-effective, reliable discrete amplification and switching in consumer, industrial, and communication equipment.

FAQ

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

The BC557B has a maximum collector-emitter voltage (V_CEO) rating of −45 VDC. This value is tested with I_C = −2.0 mA and I_B = 0, and represents the absolute maximum reverse bias the transistor can withstand before breakdown. Exceeding this voltage risks permanent damage, especially under transient conditions without clamping.

Does BC557B support lead-free soldering processes?

Yes, the BC557B (including variant BC557BZL1G) is manufactured with Pb-free terminations and complies with JEDEC J-STD-020 moisture sensitivity level (MSL) requirements. It supports standard lead-free reflow profiles up to 260°C peak, as validated in onsemi's Soldering and Mounting Techniques Reference Manual.

What is the typical DC current gain (h_FE) of BC557B at I_C = −2 mA?

At I_C = −2 mA and V_CE = −5 V, the BC557B exhibits a typical h_FE of 240, with a guaranteed minimum of 120 and maximum of 420 for B-series devices. This gain range is confirmed in the "ON CHARACTERISTICS" table on page 2 of the datasheet and is stable across −55°C to +125°C junction temperatures.

Can BC557B be used in RF amplifier applications?

Yes, the BC557B is suitable for RF amplification up to approximately 100 MHz due to its 320 MHz transition frequency (f_T) and low output capacitance (C_ob = 3.0–6.0 pF). Successful implementation requires careful impedance matching, stable biasing, and adherence to SOA limits - particularly avoiding second breakdown in pulsed operation.

How does BC557B differ from BC557A and BC557C in terms of h_FE?

The BC557B has a guaranteed h_FE range of 120–420 at I_C = −10 mA, whereas BC557A is binned 110–220 and BC557C is 180–500. All share identical voltage ratings, power dissipation, package, and pinout - only the DC current gain distribution differs, allowing designers to select based on required gain tolerance and base drive constraints.

BC557B Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-226-3, TO-92-3 Long Body

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):: 100nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 180 @ 2mA, 5V

Power - Max:: 625 mW

Frequency - Transition:: 320MHz

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92 (TO-226)

BC557B FAQ

1.How can I place an order for BC557B through Aetrix?

Please submit a Request for Quotation (RFQ) for BC557B 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 BC557B reliable?

The price and inventory of BC557B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC557B is usually 5 days.

3.What payment methods are accepted for BC557B?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC557B transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC557B?

BC557B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC557B 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 BC557B?

For technical support, including BC557B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC557B requirements.

6.How does Aetrix verify that BC557B is sourced from the original manufacturer or authorized distributors?

All BC557B 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 BC557B meets industry standards.

7.What is the process for return or replacement of BC557B?

All BC557B units undergo pre-shipment inspection (PSI). If there is an issue with BC557B, 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 BC557B part is unused and in its original packaging.

Return procedure for BC557B:

1.Submit a request within 90 days.

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

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