The BC558 is a PNP bipolar junction transistor (BJT) with the following specifications:

• Type: PNP Bipolar Junction Transistor
• Maximum Collector-Emitter Voltage (Vceo): -40V
• Maximum Collector-Base Voltage (Vcbo): -40V
• Maximum Emitter-Base Voltage (Vebo): -5V
• Maximum Collector Current (Ic): -500mA
• DC Current Gain (hFE): 40 to 800 (depending on the part number)
• Package Types: TO-92, SOT-23

The BC558 is often used in low-noise amplifier and switching applications. Its PNP configuration makes it suitable for use in circuits where negative voltage switching is required.