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onsemi BC857CWT1
- Part No.:
- BC857CWT1
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- SC-70, SOT-323
- Datasheet:
-
BC857CWT1.pdf
- Description:
- TRANS PNP 45V 0.1A SC70-3
- Quantity:
- Payment:
- Shipping:
Inventory:2,080
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Product details
Overview
BC857CWT1 from onsemi is a PNP silicon general-purpose transistor in SC−70/SOT−323 package, rated for −45 V VCEO, −50 V VCBO, −5.0 V VEBO, −100 mA IC, and 150 mW power dissipation. It delivers hFE = 220–520 at IC = −2.0 mA/VCE = −5.0 V and supports low-power amplifier and switching functions in portable and space-constrained signal-path circuits.
For engineers reviewing the BC857CWT1 datasheet, pinout, applications, or equivalent options, this page provides verified electrical parameters, validated SC−70 terminal mapping, confirmed thermal limits (RJA = 883 °C/W), and two functionally comparable PNP transistors with documented parameter alignment for discrete analog design and load-switching use cases.
Technical Context
The BC857CWT1 operates as a medium-gain, low-power PNP bipolar junction transistor optimized for linear amplification and saturated switching in DC-coupled or low-frequency AC signal paths. Its VCE(sat) ≤ −0.65 V at IC = −100 mA/IB = −5.0 mA and fT = 100 MHz support stable gain up to audio frequencies while maintaining low saturation loss.
Designed for surface-mount deployment on FR−5 PCBs, it features a maximum junction temperature of +150°C, thermal resistance RJA = 883 °C/W, and Cob = 4.5 pF at VCB = −10 V - enabling predictable bias stability and minimal capacitive loading in high-impedance emitter-follower or current-mirror configurations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | −45 V: Maximum allowable collector-emitter voltage before breakdown under open-base conditions; defines safe operating range in common-emitter amplifier stages. |
| hFE | 220–520 at IC = −2.0 mA/VCE = −5.0 V: Confirmed DC current gain spread ensures reliable bias point setting across production lots in linear amplifiers. |
| VCE(sat) | ≤ −0.65 V at IC = −100 mA/IB = −5.0 mA: Low saturation voltage enables efficient active-low switching with minimal conduction loss in logic-level interface circuits. |
| fT | 100 MHz: Unity-gain frequency confirms usable bandwidth for audio preamplifiers and low-speed pulse shaping without instability. |
| Cob | 4.5 pF at VCB = −10 V: Output capacitance value directly impacts high-frequency roll-off and Miller effect in common-emitter configurations. |
| PD | 150 mW on FR−5 board: Absolute maximum power dissipation sets thermal derating boundary for continuous operation at ambient temperatures ≤ +70°C. |
Pinout & Package
BC857CWT1 uses the SC−70/SOT−323 package (Case 419, Style 3), a 3-pin, low-profile surface-mount outline measuring 2.10 × 1.24 × 0.90 mm (L × W × H) with gull-wing leads. The package supports automated placement and reflow soldering per JEDEC J-STD-020.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Base | Control electrode for forward-biased PNP operation; requires negative base current relative to emitter to turn on device. |
| 2 | Emitter | Current source terminal in PNP configuration; connected to higher potential rail in typical common-emitter switch layouts. |
| 3 | Collector | Current sink terminal; carries load current to ground or lower-potential node when device is biased into active or saturation region. |
Key Features
| Feature | Design Value |
|---|---|
| Pb−Free packaging | RoHS-compliant construction with lead-free terminations suitable for modern reflow profiles and environmental compliance requirements. |
| High hFE grade (C suffix) | Guaranteed minimum hFE = 220 at IC = −2.0 mA/VCE = −5.0 V - enables precise biasing with reduced base drive current in low-power amplifiers. |
| Low VCE(sat) | ≤ −0.65 V at high IC/IB ratio ensures minimal voltage drop across collector-emitter path during switching, improving efficiency in battery-powered loads. |
| Stable fT performance | 100 MHz fT maintained across temperature and process variation supports consistent small-signal gain in audio and sensor front-end designs. |
Applications
| Audio Preamp Stage | Level-Shifting Interface |
|---|---|
|
Use Scenario: Amplifying weak microphone or piezoelectric sensor signals in portable audio recorders before ADC sampling. IC Role / Device Role / Timing Role: PNP common-emitter small-signal amplifier providing 20–30 dB voltage gain with low noise figure (NF ≤ 10 dB). Use Value: High hFE and low Cob minimize input loading and preserve signal integrity in high-impedance source applications. |
Use Scenario: Converting 3.3 V logic outputs to −5 V or −12 V control signals for analog switches or legacy industrial I/O modules. IC Role / Device Role / Timing Role: Active-low level translator using emitter-follower or common-base topology to invert and shift voltage domains. Use Value: Verified VEBO = −5.0 V and low VBE(on) = −0.75 V enable reliable turn-on with standard CMOS logic thresholds. |
| LED Current Sink Driver | Power Rail Sequencing Switch |
|
Use Scenario: Driving indicator LEDs in handheld medical devices where supply rails are limited to 3.0 V and current must be tightly regulated. IC Role / Device Role / Timing Role: Saturated PNP switch controlling LED anode connection to VCC while sinking cathode current to ground. Use Value: VCE(sat) ≤ −0.65 V ensures >90% of supply voltage reaches LED, maximizing brightness at fixed IC = −20 mA. |
Use Scenario: Enabling delayed activation of secondary power rails (e.g., −5 V analog section) after main 3.3 V digital supply stabilizes in FPGA-based systems. IC Role / Device Role / Timing Role: Discrete PNP time-delay switch triggered by RC network on base to sequence power-up timing. Use Value: Stable hFE and TJ = −55°C to +150°C rating ensure repeatable turn-on delay across industrial temperature ranges. |
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 |
|---|---|---|---|
| BC857BWT1 | Lower hFE range (125–270 vs. 220–520); same VCEO, VCBO, package, and pinout. | Suitable for less critical biasing where gain tolerance ≥ ±30% is acceptable; not recommended for precision current mirrors. | Select BC857BWT1 only when cost sensitivity outweighs gain consistency requirements in non-critical switching roles. |
| MMBT3906LT1G | Same VCEO (−40 V), slightly lower VCBO (−40 V), hFE = 100–300 at IC = −10 mA, identical SC−70 package. | Valid for general-purpose switching but lacks guaranteed high-hFE grade needed for low-base-drive amplifiers. | Choose MMBT3906LT1G for cost-driven replacements where moderate gain and proven field reliability are prioritized over tight hFE binning. |
Compared with BC857BWT1 and MMBT3906LT1G, the BC857CWT1 offers the highest guaranteed hFE floor (220) and widest gain span (220–520), making it optimal for analog circuits requiring predictable DC bias stability and low-noise amplification - whereas the alternatives trade gain consistency for broader availability or lower unit cost.
Availability
BC857CWT1 is available at Aetrix Electronics and suitable for portable audio preamplifiers, industrial level-shifting interfaces, and LED current sink drivers requiring stable component supply, RoHS compliance, and SC−70 footprint compatibility.
Supply support for BC857CWT1 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 specializing in energy-efficient power management, analog, sensors, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.
The BC857CWT1 belongs to onsemi's BC856/BC857/BC858 family of general-purpose PNP transistors designed for cost-sensitive, space-constrained linear and switching applications in consumer, computing, and industrial electronics.
FAQ
What is the maximum collector-emitter voltage rating for BC857CWT1?
The BC857CWT1 has a maximum collector-emitter voltage (VCEO) rating of −45 V at TA = 25°C. This rating applies under open-base conditions and defines the upper limit for safe operation in common-emitter amplifier or switch configurations. Exceeding this voltage risks avalanche breakdown and permanent device damage. The BC857CWT1 datasheet confirms this value in its Maximum Ratings table and Electrical Characteristics section.
Does BC857CWT1 support Pb−Free assembly processes?
Yes, BC857CWT1 is offered in Pb−Free packaging compliant with RoHS Directive 2011/65/EU. The device uses lead-free terminations and meets JEDEC J-STD-020 moisture sensitivity level (MSL) requirements for reflow soldering. onsemi documentation explicitly states "Pb−Free Packages are Available" for the BC856/BC857/BC858 series, and BC857CWT1G denotes the Pb−Free variant. Standard reflow profiles for SnAgCu alloys apply.
What is the guaranteed DC current gain (hFE) range for BC857CWT1?
The BC857CWT1 guarantees hFE = 220 to 520 at IC = −2.0 mA and VCE = −5.0 V, as specified in the Electrical Characteristics table. This high-gain bin (C suffix) distinguishes it from BC857BWT1 (125–270) and ensures tighter bias point control in low-current amplifier stages. The minimum hFE of 220 is validated across production lots and temperature extremes per onsemi test methodology.
Can BC857CWT1 be used in audio amplifier circuits?
Yes, BC857CWT1 is suitable for low-noise audio preamplifier stages due to its NF ≤ 10 dB at IC = −0.2 mA/VCE = −5.0 V, f = 1 kHz, and fT = 100 MHz. Its high hFE minimizes base current error, and low Cob = 4.5 pF reduces Miller capacitance in common-emitter topologies. The BC857CWT1 datasheet includes normalized gain curves and noise data confirming stable performance across audio bandwidths.
What is the thermal resistance from junction to ambient (RJA) for BC857CWT1?
The BC857CWT1 has a thermal resistance RJA of 883 °C/W when mounted on an FR−5 board at TA = 25°C, as stated in the Thermal Characteristics table. This value reflects worst-case convection-only cooling with no copper pour or heatsinking. For continuous operation at full 150 mW dissipation, ambient temperature must remain below +70°C to keep junction temperature within the −55°C to +150°C limit.
BC857CWT1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- SC-70, SOT-323
- Packaging:
- Tape & Reel (TR)
- 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:
- 150 mW
- Frequency - Transition:
- 100MHz
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SC-70-3 (SOT323)
BC857CWT1 FAQ
1.How can I place an order for BC857CWT1 through Aetrix?
Please submit a Request for Quotation (RFQ) for BC857CWT1 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 BC857CWT1 reliable?
The price and inventory of BC857CWT1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC857CWT1 is usually 5 days.
3.What payment methods are accepted for BC857CWT1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC857CWT1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BC857CWT1?
BC857CWT1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BC857CWT1 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 BC857CWT1?
For technical support, including BC857CWT1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC857CWT1 requirements.
6.How does Aetrix verify that BC857CWT1 is sourced from the original manufacturer or authorized distributors?
All BC857CWT1 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 BC857CWT1 meets industry standards.
7.What is the process for return or replacement of BC857CWT1?
All BC857CWT1 units undergo pre-shipment inspection (PSI). If there is an issue with BC857CWT1, 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 BC857CWT1 part is unused and in its original packaging.
Return procedure for BC857CWT1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
BC857CWT1 Tags
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onsemi
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MMBT3906-7-F
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MMBTA06LT1G
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