BF421 – PHILIPS

Overview

The PHILIPS BF421 is a high-voltage, silicon epitaxial planar PNP transistor designed for robust performance in demanding electronic circuits. Its primary function is amplifying or switching, with a critical operational characteristic being its high collector-emitter voltage (Vceo) rating, enabling its use in applications requiring significant voltage headroom. A common design trade-off when utilizing such high-voltage transistors is the potential for increased leakage current at elevated temperatures, necessitating careful thermal management and biasing strategies to maintain signal integrity and prevent parasitic conduction, especially in sensitive video amplifier stages.

Key Features

• High Voltage PNP Epitaxial Planar Transistor
• Collector-Emitter Voltage (Vceo): 200 V
• Continuous Collector Current (Ic): 50 mA
• Power Dissipation (Pd): 500 mW
• TO-92 Through-Hole Package
• Complementary NPN Type: BF420

Applications

The component is engineered for deployment in systems requiring high reliability and performance under specific operating conditions. It provides functional stability across the stated design envelope.

• High-voltage video amplifier stages (e.g., RGB cathode current control)
• Telephone wireline interface circuits (hook switches)
• Low-frequency signal amplification in high-impedance circuits
• Voltage regulation circuits requiring high breakdown voltage