BC857A

Overview

The BC857A is a PNP silicon small-signal bipolar junction transistor manufactured by Taiwan Semiconductor Corporation. It operates with a maximum collector current of 100 mA and features a collector-emitter voltage rating of 45 V. The device utilizes an SOT-23 surface-mount package, ensuring compatibility with automated assembly processes. Key electrical characteristics include a DC current gain (hFE) range of 125 to 250 for the 'A' grade variant. The component supports a maximum power dissipation of 200 mW and functions within a temperature range extending up to +150 °C.

Feature Summary

• PNP polarity configuration suitable for general-purpose switching and amplification applications
• High DC current gain classification providing reliable signal control performance
• Compact SOT-23 surface-mount design facilitating efficient PCB layout

Applications

• General-purpose signal amplification circuits
• Low-power switching applications
• Audio pre-amplifier stages

Procurement Notes

Verify the manufacturer designation explicitly as Taiwan Semiconductor Corporation during sourcing. Confirm the specific suffix indicates the standard BC857A grade with hFE between 125 and 250. Ensure the package type matches the required SOT-23 footprint for your assembly process. Cross-reference datasheets to confirm thermal resistance values if operating near maximum limits.

Selection Notes

Select this component when a PNP transistor with moderate voltage handling and defined gain bands is required. The 45 V rating suits low-voltage logic interfacing. Consider the SOT-23 package constraints regarding thermal dissipation capabilities. Verify that the 100 mA current limit aligns with the load requirements of the target circuit design.

Part Context

This part belongs to the widely adopted BC857 series of small-signal transistors. The BC857A specifically denotes a binning category for current gain, distinguishing it from other variants like BC857B or BC857C which offer different hFE ranges. It serves as a standard discrete semiconductor solution for consumer electronics and industrial control modules.

Replacement Considerations

Compatible substitutes include BC857A from manufacturers such as Nexperia, onsemi, and Diodes Incorporated. Ensure replacement parts maintain the same SOT-23 package and meet the 45 V / 100 mA specifications.