onsemi BC857BWT1

Overview

BC857BWT1 from onsemi is a PNP silicon general-purpose transistor in SC-70/SOT-323 package, rated for −45 V V_CEO, −50 V V_CBO, −5.0 V V_EBO, −100 mA I_C, and 150 mW power dissipation. It delivers h_FE = 220–475 at I_C = −2.0 mA, V_CE = −5.0 V, and f_T = 100 MHz, used in low-power signal amplification and switching circuits on compact PCBs.

For engineers reviewing the BC857BWT1 datasheet, pinout, applications, or equivalent options, this page provides verified electrical parameters, terminal mapping, thermal behavior, real-world use cases, and validated alternative transistors for discrete analog design, bias networks, and level-shifting stages in consumer and industrial electronics.

Technical Context

The BC857BWT1 operates as a medium-gain, low-power PNP bipolar junction transistor optimized for linear amplification and saturated switching. Its DC current gain (h_FE) is specified across two test conditions: 220–475 at I_C = −2.0 mA and 125–290 at I_C = −10 mA, enabling stable biasing in emitter-follower and common-emitter configurations.

It features V_CE(sat) ≤ −0.65 V at I_C = −100 mA / I_B = −5.0 mA and V_BE(sat) ≤ −0.9 V under the same conditions, supporting efficient low-voltage switching. Thermal resistance R_JA = 883 °C/W on FR-5 board confirms suitability for thermally constrained surface-mount layouts without forced cooling.

Key Specifications

Pinout & Package

BC857BWT1 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 with gull-wing leads. The package supports automated placement and reflow soldering per JEDEC standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC857BWT1, BC857BW,115 offers marginally better switching efficiency in SC-70 form factor, while MMBT3906LT1G trades package compatibility for increased current capacity-neither is pin-compatible, but both serve overlapping functional roles in discrete analog subsystems.

Availability

BC857BWT1 is available at Aetrix Electronics and suitable for audio signal amplification, level-shifting interfaces, LED driver switches, and current mirror references requiring stable component supply across high-mix, low-volume production runs.

Supply support for BC857BWT1 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 and sensing solutions, with leadership in automotive, industrial, cloud, and medical markets.

The BC857BWT1 belongs to onsemi's general-purpose bipolar transistor family, engineered for reliable, low-cost amplification and switching in space-constrained, low-power surface-mount applications.

FAQ

What is the maximum collector-emitter voltage rating for BC857BWT1?

The BC857BWT1 has a guaranteed V_CEO rating of −45 V at T_A = 25°C. This value represents the maximum reverse-biased voltage the transistor can withstand between collector and emitter before breakdown occurs. Exceeding −45 V risks irreversible damage, and derating is recommended for operation above 25°C ambient or under transient conditions. The BC857BWT1 datasheet specifies this parameter in its Maximum Ratings table.

Does BC857BWT1 support Pb-free soldering processes?

Yes, BC857BWT1 is manufactured with Pb-free terminations and complies with RoHS Directive 2011/65/EU. It is qualified for standard reflow soldering profiles per J-STD-020, with moisture sensitivity level (MSL) 1 - meaning it may be stored indefinitely at ≤30°C/85% RH without baking. The "G" suffix variant (BC857BWT1G) explicitly denotes the Pb-free version, though the base BC857BWT1 is also Pb-free per onsemi's manufacturing policy.

What is the typical DC current gain (h_FE) range for BC857BWT1 at I_C = −2.0 mA?

The BC857BWT1 exhibits h_FE = 220–475 when tested at I_C = −2.0 mA and V_CE = −5.0 V, as confirmed in the Electrical Characteristics table of the official datasheet. This binning ("B" grade) ensures consistent gain performance across production lots, reducing the need for circuit trimming or gain-dependent calibration in production assemblies using BC857BWT1.

Can BC857BWT1 be used in high-frequency amplifier designs?

Yes, BC857BWT1 supports high-frequency operation with a current-gain bandwidth product (f_T) of 100 MHz at I_C = −10 mA and V_CE = −5.0 V. Its 4.5 pF output capacitance (C_ob) and low base resistance enable stable gain up to ~10 MHz in common-emitter configurations. For RF applications beyond 20 MHz, layout parasitics and bias network design become critical - the BC857BWT1 itself is not optimized for RF power amplification but performs reliably in broadband preamp and IF stages.

How does the thermal resistance of BC857BWT1 affect its power handling on a standard PCB?

BC857BWT1 has R_JA = 883 °C/W on FR-5 board, meaning each milliwatt of dissipated power raises the junction temperature by 0.883°C above ambient. At its rated 150 mW P_D, this yields a theoretical ΔT of 132°C - so operation near maximum ambient (e.g., 85°C) risks exceeding the 150°C T_J limit. Derating to ≤75 mW is recommended for sustained operation above 50°C ambient. The BC857BWT1 datasheet provides transient thermal curves (Figure 13) to model pulsed loads accurately.