BC857S Equivalent & Substitute Parts

Part Overview

The BC857S is a dual PNP bipolar junction transistor (BJT) manufactured by onsemi, housed in a 6-pin SOT-363 (SC-88/SC-70-6) surface mount package. This component is classified as obsolete, though inventory remains available. The BC857S is designed for general-purpose switching and amplification applications requiring dual PNP transistor functionality in a compact form factor. Due to its obsolete status, equivalent and substitute parts from active product lines are necessary for new designs and long-term supply chain continuity.

Key Parameters

Parameter	BC857S Specification
Transistor Type	2 PNP (Dual)
Collector Current (Ic) Max	200mA
Collector-Emitter Breakdown Voltage (Max)	45V
Vce Saturation (Max) @ Ib, Ic	650mV @ 5mA, 100mA
DC Current Gain (hFE) Min @ Ic, Vce	125 @ 2mA, 5V
Power Dissipation (Max)	300mW
Transition Frequency	200MHz
Operating Temperature Range	-55°C to 150°C (TJ)
Package / Case	6-TSSOP, SC-88, SOT-363
Mounting Type	Surface Mount
Moisture Sensitivity Level (MSL)	1 (Unlimited)

Substitute Part Grouping Explanation

Substitution of the BC857S is determined by the following critical parameters:

Electrical Compatibility Requirements:

Transistor configuration: 2 PNP (Dual) topology
Collector-Emitter breakdown voltage: minimum 45V
Maximum collector current: minimum 200mA
Power dissipation: minimum 300mW
Transition frequency: minimum 200MHz
DC current gain (hFE): minimum 125 @ 2mA, 5V
Operating temperature range: -55°C to 150°C

Mechanical Compatibility Requirements:

Package type: 6-TSSOP, SC-88, or SOT-363
Surface mount configuration
Pin count: 6 pins

Substitute parts are grouped into two categories:

Category 1: Direct Electrical Equivalents (200mA, 45V, 200MHz) Parts that maintain the full electrical specification of the BC857S, including 200mA collector current and 200MHz transition frequency.

Category 2: Functional Substitutes (100mA, 45V, 100MHz) Parts that operate at reduced collector current (100mA) and transition frequency (100MHz) but maintain 45V breakdown voltage and compatible package. These are suitable for applications not requiring the full 200mA current capability.

Category 3: Alternative Voltage Class (200mA, 40V, 250MHz) Parts with slightly reduced breakdown voltage (40V) but enhanced transition frequency (250MHz) and maintained 200mA current capability. Suitable for applications with lower voltage requirements.

Parameter Comparison

Part Number	Manufacturer	Ic (Max)	Vce(br) (Max)	hFE Min @ Ic, Vce	Power (Max)	Freq (MHz)	Temp Range	Package	Status
BC857S	onsemi	200mA	45V	125 @ 2mA, 5V	300mW	200	-55 to 150°C	SOT-363	Obsolete
BC857S-TP	Micro Commercial Co	200mA	45V	125 @ 2mA, 5V	300mW	200	-55 to 150°C	SOT-363	Active
BC857BDW1T1G	onsemi	100mA	45V	220 @ 2mA, 5V	380mW	100	-55 to 150°C	SOT-363	Active
BC857CDW1T1G	onsemi	100mA	45V	420 @ 2mA, 5V	380mW	100	-55 to 150°C	SOT-363	Active
SBC857BDW1T1G	onsemi	100mA	45V	220 @ 2mA, 5V	380mW	100	-55 to 150°C	SOT-363	Active
SBC857CDW1T1G	onsemi	100mA	45V	420 @ 2mA, 5V	380mW	100	-55 to 150°C	SOT-363	Active
NST45010MW6T1G	onsemi	100mA	45V	220 @ 2mA, 5V	380mW	100	-55 to 150°C	SOT-363	Active
BC857BS,115	Nexperia USA Inc.	100mA	45V	200 @ 2mA, 5V	200mW	100	-55 to 150°C	6-TSSOP	Active
BC857BS,135	Nexperia USA Inc.	100mA	45V	200 @ 2mA, 5V	200mW	100	-55 to 150°C	6-TSSOP	Active
MBT3906DW1T1G	onsemi	200mA	40V	100 @ 10mA, 1V	150mW	250	-55 to 150°C	SOT-363	Active
SMBT3906DW1T1G	onsemi	200mA	40V	100 @ 10mA, 1V	150mW	250	-55 to 150°C	SOT-363	Active

Engineering Selection Recommendations

Primary Recommendation: BC857S-TP (Micro Commercial Co)

BC857S-TP is the direct functional equivalent of the obsolete BC857S. It maintains identical electrical specifications across all critical parameters: 200mA collector current, 45V breakdown voltage, 200MHz transition frequency, 300mW power dissipation, and 125 hFE minimum. The part is in active production status with RoHS3 compliance and AEC-Q101 automotive qualification available. This part is suitable for direct replacement in existing designs without circuit modification.

Secondary Recommendation: SBC857BDW1T1G or SBC857CDW1T1G (onsemi, Automotive Grade)

For applications requiring automotive-grade components with AEC-Q101 qualification, SBC857BDW1T1G and SBC857CDW1T1G provide active production status with automotive qualification. These parts operate at 100mA collector current and 100MHz transition frequency, representing a functional downgrade from the BC857S. Selection between these two variants depends on DC current gain requirements: SBC857BDW1T1G provides 220 hFE minimum, while SBC857CDW1T1G provides 420 hFE minimum. These parts are suitable only for applications where the reduced current and frequency specifications are acceptable.

Alternative Recommendation: MBT3906DW1T1G or SMBT3906DW1T1G (onsemi)

For applications with voltage headroom below 45V, MBT3906DW1T1G and SMBT3906DW1T1G offer 40V breakdown voltage with enhanced 250MHz transition frequency and maintained 200mA collector current. SMBT3906DW1T1G carries automotive qualification. These parts are suitable for designs operating at reduced voltage levels where the enhanced frequency response provides performance benefits.

Compliance Considerations:

All recommended substitute parts maintain MSL 1 (Unlimited) moisture sensitivity rating, REACH Unaffected status, and EAR99 export classification consistent with the BC857S. RoHS3 compliance is standard across active production parts. Automotive-grade variants (SBC series) include AEC-Q101 qualification for applications requiring automotive reliability standards.

Frequently Asked Questions (FAQ)

Q: Can BC857S-TP be used as a direct replacement for BC857S in all applications?

A: Yes. BC857S-TP maintains identical electrical specifications: 200mA collector current, 45V breakdown voltage, 200MHz transition frequency, 300mW power dissipation, and 125 hFE minimum. The part operates across the same temperature range (-55°C to 150°C) and uses the same SOT-363 package. No circuit modifications are required.

Q: What is the difference between BC857BDW1T1G and BC857CDW1T1G?

A: Both parts operate at 100mA collector current and 100MHz transition frequency with 45V breakdown voltage. The primary difference is DC current gain: BC857BDW1T1G provides 220 hFE minimum, while BC857CDW1T1G provides 420 hFE minimum. Selection depends on the application's gain requirements. Both are suitable substitutes only for applications that can tolerate reduced current and frequency specifications compared to BC857S.

Q: Are SBC857 parts suitable replacements for BC857S?

A: SBC857BDW1T1G and SBC857CDW1T1G are functional substitutes with reduced electrical specifications. They operate at 100mA (versus 200mA) and 100MHz (versus 200MHz). These parts are suitable only for applications where the reduced current and frequency ratings are acceptable. The advantage is automotive-grade qualification (AEC-Q101) for applications requiring automotive reliability standards.

Q: What is the difference between BC857BS,115 and BC857BS,135?

A: Both parts are manufactured by Nexperia and provide identical electrical specifications: 100mA collector current, 45V breakdown voltage, 100MHz transition frequency, and 200 hFE minimum. The difference is packaging: BC857BS,115 is supplied in Cut Tape (CT) & Digi-Reel format, while BC857BS,135 is supplied in Tape & Reel (TR) format. Both use 6-TSSOP package and carry automotive qualification (AEC-Q101).

Q: Can MBT3906DW1T1G replace BC857S?

A: MBT3906DW1T1G is a functional alternative with trade-offs. It maintains 200mA collector current and adds enhanced 250MHz transition frequency, but reduces breakdown voltage to 40V. This part is suitable only for applications operating below 40V where the enhanced frequency response provides benefits. It is not suitable for applications requiring 45V breakdown voltage.

Q: What does MSL 1 (Unlimited) mean for moisture sensitivity?

A: MSL 1 (Unlimited) indicates the component has no moisture sensitivity restrictions. The part can be stored and handled without special moisture control measures, and there are no time-to-reflow limitations. This applies to all BC857S equivalents and substitutes listed.

Q: Are all substitute parts RoHS3 compliant?

A: All active production substitute parts listed are RoHS3 compliant. The obsolete BC857S does not carry RoHS3 compliance designation. RoHS3 compliance is a standard requirement for all active onsemi and Nexperia production parts.

Q: What is the significance of AEC-Q101 qualification?

A: AEC-Q101 is an automotive industry qualification standard for discrete semiconductors. Parts carrying this qualification (SBC857 series, SMBT3906DW1T1G) have undergone rigorous testing for automotive applications including temperature cycling, thermal shock, and reliability validation. This qualification is required for automotive-grade designs but is not necessary for general industrial or consumer applications.

Q: Can NST45010MW6T1G be used instead of BC857S?

A: NST45010MW6T1G is a matched pair variant with identical electrical specifications to BC857BDW1T1G: 100mA collector current, 45V breakdown voltage, 100MHz transition frequency, and 220 hFE minimum. The "matched pair" designation indicates tighter parameter matching between the two transistors within the package. This part is suitable only for applications where reduced current and frequency specifications are acceptable and where matched pair characteristics provide design benefits.

Q: What is the difference between SC-88, SC-70-6, and SOT-363 package designations?

A: SC-88, SC-70-6, and SOT-363 are equivalent package designations for the same 6-pin surface mount package. All BC857S equivalents and substitutes use this identical package form factor. The different naming conventions reflect different standardization bodies (JEDEC, manufacturer-specific) but represent the same physical package with identical pin configuration and footprint.

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