BC858 PNP Transistor Technical Summary

Overview

The BC858 is a general-purpose PNP bipolar junction transistor (BJT) housed in an SC-75 plastic package. Designed for low-power amplification and switching applications, this transistor offers reliable performance with a balance of current and voltage handling capabilities. Its compact form factor makes it suitable for space-constrained designs, while its electrical characteristics ensure versatility across a range of electronic circuits.

Features

• Polarity: PNP configuration
• Maximum Collector Current (Ic): 100 mA
• Maximum Collector-Emitter Voltage (V_CEO): 65 V
• Package Type: SC-75 (SOT-416), a compact surface-mount package
• Low Power Dissipation: Suitable for energy-efficient designs
• High Current Gain (h_FE): Ensures effective signal amplification
• RoHS Compliant: Meets environmental standards

Applications

The BC858 is widely used in low-power electronic circuits where efficient switching or signal amplification is required. Common applications include:

• Signal Amplification: Audio pre-amplifiers, sensor interfaces, and small-signal amplification stages.
• Switching Circuits: On/off control in low-current loads, such as relays, LEDs, and small motors.
• Consumer Electronics: Remote controls, portable devices, and battery-operated gadgets.
• Industrial Control Systems: Logic level shifting and interface circuits.
• Automotive Electronics: Non-critical low-voltage switching applications.

Electrical Characteristics

The following table summarizes the key electrical parameters of the BC858 transistor under standard test conditions (unless otherwise specified):

Absolute Maximum Ratings

• Collector-Emitter Voltage (V_CEO): 65 V
• Collector-Base Voltage (V_CBO): 80 V
• Emitter-Base Voltage (V_EBO): 5 V
• Collector Current (I_C): 100 mA (continuous)
• Total Power Dissipation (P_tot): Typically 250 mW at 25°C (derate above this temperature)
• Operating Junction Temperature (T_j): -55°C to +150°C
• Storage Temperature (T_stg): -55°C to +150°C

Typical Performance Characteristics

• DC Current Gain (h_FE): 125 to 800 (varies with collector current and temperature)
• Collector-Emitter Saturation Voltage (V_CE(sat)): ~0.3 V at I_C = 10 mA, I_B = 1 mA
• Transition Frequency (f_T): Typically 100 MHz (ensures good high-frequency response)
• Noise Figure: Low noise performance, suitable for analog signal processing

Package Information

The BC858 is housed in an SC-75 (SOT-416) surface-mount package, which is designed for automated assembly processes. Below are the key mechanical details:

SC-75 (SOT-416) Package Dimensions

• Package Length: 1.6 mm (max)
• Package Width: 1.2 mm (max)
• Package Height: 0.6 mm (max)
• Lead Pitch: 0.65 mm (standard for SC-75)
• Termination: Tin-plated leads for solderability
• Moisture Sensitivity Level (MSL): MSL 1 (unlimited floor life at ≤30°C/85% RH)

Recommended PCB Footprint

For optimal soldering and thermal performance, the following footprint is recommended:

• Pad Layout: Three pads (Emitter, Base, Collector) with 0.65 mm spacing
• Pad Dimensions: 0.8 mm x 0.6 mm (rectangular pads for stability)
• Thermal Considerations: A small ground pad or copper pour under the package can improve heat dissipation

Reliability and Compliance

The BC858 transistor adheres to industry standards for reliability and environmental safety:

• RoHS Compliance: Free from restricted substances (Pb, Cd, Hg, etc.)
• ESD Protection: Handles minor electrostatic discharge (ESD) during handling
• Flammability Rating: UL 94V-0 compliant for plastic material

Handling and Storage Guidelines

To ensure longevity and performance:

• Store in anti-static bags or conductive foam to prevent ESD damage.
• Use within 12 months of purchase for optimal solderability.
• Avoid exposure to high humidity (>85% RH) during storage.
• Follow JEDEC J-STD-020 guidelines for reflow soldering profiles.

Conclusion

The BC858 PNP transistor is a versatile, low-power component ideal for amplification and switching tasks in compact electronic designs. Its robust electrical characteristics, combined with the SC-75 package’s small footprint, make it a preferred choice for consumer, industrial, and automotive applications. Engineers can rely on its consistent performance and compliance with environmental standards for sustainable product development.