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

Nexperia USA Inc. BC857B-QR

Name: BC857B-QR
Brand: Nexperia USA Inc.
SKU: BC857B-QR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC857B-QR

Manufacturer:: Nexperia USA Inc.

Category:: Single Bipolar Transistors

Package:: TO-236-3, SC-59, SOT-23-3

Datasheet:: BC857B-QR.pdf

Description:: TRANS PNP 45V 0.1A TO-236AB

Quantity:: RFQ Add To RFQ list

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Inventory:20,276

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Product details

Overview

BC857B-Q from Nexperia is a PNP general-purpose bipolar junction transistor in SOT23 (TO-236AB) package, rated for −45 V V_CEO, −100 mA I_C, and DC current gain (h_FE) of 220–475 at V_CE = −5 V and I_C = −2 mA. It serves as a low-voltage switching or linear amplification device in automotive signal conditioning and power management circuits.

For engineers reviewing the BC857B-Q datasheet, BC857B-Q pinout, BC857B-Q application, or BC857B-Q equivalent, this page delivers verified electrical parameters, AEC-Q101 qualification status, thermal resistance (500 K/W), saturation voltage (V_CE(sat) ≤ −650 mV at I_C = −100 mA), and exact pin mapping - all essential for automotive-grade PCB layout and reliability validation.

Technical Context

This PNP transistor operates with open-base collector-emitter breakdown of −45 V and emitter-base breakdown of −5 V, supporting robust biasing in negative-rail signal paths. Its h_FE range (220–475) ensures predictable current amplification across temperature (−55 °C to +150 °C) and collector currents from −1 mA to −100 mA.

V_CE(sat) remains ≤ −650 mV under high-current switching (I_C = −100 mA, I_B = −5 mA), enabling efficient low-side load control. The 4.5 pF collector capacitance and 100 MHz f_T support stable operation up to audio and low-speed digital frequencies without unintended oscillation.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−45 V: Maximum safe collector-emitter voltage with base open; defines rail compatibility in 36 V automotive systems.
I_C	−100 mA continuous: Supports driving small relays, LEDs, or logic-level inputs without external heat sinking.
h_FE	220–475 at V_CE = −5 V, I_C = −2 mA: Enables precise base resistor selection for stable DC bias in amplifier stages.
V_CE(sat)	≤ −650 mV at I_C = −100 mA, I_B = −5 mA: Minimizes conduction loss in high-duty-cycle switching applications.
R_th(j-a)	500 K/W on FR4 PCB: Determines junction temperature rise under 250 mW dissipation; critical for thermal margin in sealed enclosures.
f_T	100 MHz: Confirms suitability for audio preamplifiers and low-speed digital interface buffering without phase shift issues.
AEC-Q101	Qualified: Meets stress-test requirements for automotive discrete semiconductors, including temperature cycling and HTRB.

Pinout & Package

SOT23 (TO-236AB) surface-mount plastic package with 3 leads; 1.9 mm × 1.3 mm footprint, 0.95 mm height, and standard reflow-compatible solder pad layout.

Pin/Terminal	Circuit Role	Design Meaning
1	Base (B)	Current-controlled input node; requires series resistor to limit I_B and ensure saturation or cutoff per drive logic.
2	Emitter (E)	Common terminal tied to higher potential rail (e.g., battery +12 V); polarity defines PNP operation.
3	Collector (C)	Output terminal sourcing current to load; connects to switched ground or lower-potential node.

Key Features

Feature	Design Value
AEC-Q101 qualified	Validated for automotive under-hood environments including 1000-hour high-temperature reverse bias (HTRB) and temperature cycling.
Low V_CE(sat)	−650 mV max at full rated current enables >93% efficiency in 12 V load switches (e.g., HVAC fan control).
Wide h_FE range	220–475 allows consistent gain across production lots without binning, simplifying BOM management for Tier 1 suppliers.
Small SOT23 footprint	Enables high-density placement on compact ECUs and ADAS sensor modules without thermal crowding.
−5 V V_EBO	Permits reliable base-emitter reverse biasing during PWM dead-time, preventing latch-up in half-bridge drivers.

Applications

Automotive Door Module

Industrial Sensor Interface

Use Scenario: Driving window lift motor enable signals and mirror fold/unfold relays in body control modules.

IC Role / Device Role / Timing Role: PNP switch controlling 12 V relay coils with fast turn-off via base pull-down.

Use Value: −650 mV V_CE(sat) minimizes coil heating during frequent actuation cycles; AEC-Q101 ensures 15-year field reliability.

Use Scenario: Level-shifting and buffering analog sensor outputs (e.g., thermistor, pressure transducer) into ADC inputs.

IC Role / Device Role / Timing Role: Emitter-follower amplifier providing low-output-impedance drive while isolating sensitive front-end circuitry.

Use Value: 220–475 h_FE guarantees stable gain over −40 °C to +125 °C ambient, eliminating calibration drift.

LED Tail Light Driver

Power Supply Enable Circuit

Use Scenario: Switching high-brightness brake/turn LEDs in rear lighting assemblies with PWM dimming.

IC Role / Device Role / Timing Role: Low-side current sink configured as PNP high-side switch with base driven by MCU GPIO.

Use Value: 100 MHz f_T supports clean 1–2 kHz PWM edges without overshoot; 4.5 pF C_c prevents RF coupling into CAN bus traces.

Use Scenario: Enabling 5 V or 3.3 V LDOs in infotainment head units based on ignition key position detection.

IC Role / Device Role / Timing Role: Logic-level translator converting 3.3 V microcontroller output to 12 V enable signal for downstream regulators.

Use Value: −45 V V_CEO withstands load-dump transients up to ISO 7637-2 Pulse 5a; −5 V V_EBO blocks reverse leakage during sleep mode.

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
BC857B,115 (Nexperia)	No "-Q" suffix; not AEC-Q101 qualified; identical electrical specs and SOT23 package.	Restricted to consumer or industrial use where automotive qualification is not required.	Select when cost sensitivity outweighs automotive compliance; same footprint and schematic symbol.
MMBT3906LT1G (onsemi)	V_CEO = −40 V (5 V lower); h_FE = 100–300 (narrower range); also AEC-Q101 qualified.	Marginally lower voltage headroom limits use in 42 V mild-hybrid systems; tighter h_FE reduces design flexibility.	Choose only if legacy BOM already uses MMBT3906LT1G; verify V_CEO margin in 36 V nominal systems.

Compared with BC857B-Q, BC857B,115 offers identical performance at lower cost but lacks automotive qualification, while MMBT3906LT1G trades voltage margin and gain spread for broader industry adoption - making BC857B-Q optimal for new AEC-Q101-compliant designs requiring guaranteed −45 V operation and wide h_FE.

Availability

BC857B-Q is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor interfaces, LED lighting control, and power supply enable circuits requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for BC857B-Q 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

Nexperia is a global semiconductor expert focused on high-volume, high-reliability discrete and logic devices, with core R&D in Nijmegen, Netherlands.

The BC856-Q/BC857-Q/BC858-Q family was designed specifically for automotive signal switching and amplification, emphasizing AEC-Q101 compliance, thermal robustness on FR4 PCBs, and tight parametric consistency across production lots.

FAQ

What is the maximum allowable junction temperature for BC857B-Q?

The absolute maximum junction temperature (T_j) is 150 °C, as defined in Table 6 of the datasheet. This limit applies under all operating conditions, including pulsed and continuous modes. Derating is required above Tamb = 25 °C using the specified R_th(j-a) = 500 K/W to ensure T_j stays within specification during sustained 100 mA operation.

Does BC857B-Q support operation at −55 °C ambient?

Yes - the device is fully characterized from −55 °C to +150 °C ambient (T_amb). Figures 6–9 confirm h_FE, V_BE, and V_CE(sat) behavior across this full range, with no parameter degradation at cold extremes. This makes it suitable for engine bay and exterior lighting applications.

How does the "-Q" suffix affect packaging or marking?

The "-Q" suffix denotes AEC-Q101 qualification and corresponds to specific wafer fab and assembly/test flow controls. Marking code is "3F%", where "%" is a site-specific placeholder; physical SOT23 package dimensions and lead finish (tin-plated) match non-Q variants exactly.

Can BC857B-Q replace BC857C-Q in a design?

No - BC857C-Q has h_FE = 420–800, significantly higher than BC857B-Q's 220–475. Substituting without recalculating base drive risks insufficient saturation or excessive base current consumption. Electrical differences are documented in Tables 2 and 4 of the datasheet.

BC857B-QR Specifications

Product attributes: Attribute value

Manufacturer:: Nexperia USA Inc.

Series:: -

Package/Case:: TO-236-3, SC-59, SOT-23-3

Packaging:: Tape & Reel (TR)

Product Status:: Active

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:: 220 @ 2mA, 5V

Power - Max:: 250 mW

Frequency - Transition:: 100MHz

Operating Temperature:: 150°C (TJ)

Grade:: Automotive

Qualification:: AEC-Q101

Mounting Type:: Surface Mount

Supplier Device Package:: TO-236AB

BC857B-QR FAQ

1.How can I place an order for BC857B-QR through Aetrix?

Please submit a Request for Quotation (RFQ) for BC857B-QR 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 BC857B-QR reliable?

The price and inventory of BC857B-QR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC857B-QR is usually 5 days.

3.What payment methods are accepted for BC857B-QR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC857B-QR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC857B-QR?

BC857B-QR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC857B-QR 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 BC857B-QR?

For technical support, including BC857B-QR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC857B-QR requirements.

6.How does Aetrix verify that BC857B-QR is sourced from the original manufacturer or authorized distributors?

All BC857B-QR 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 BC857B-QR meets industry standards.

7.What is the process for return or replacement of BC857B-QR?

All BC857B-QR units undergo pre-shipment inspection (PSI). If there is an issue with BC857B-QR, 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 BC857B-QR part is unused and in its original packaging.

Return procedure for BC857B-QR:

1.Submit a request within 90 days.

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

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