BC558 PNP
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The BC558 is a very common, general-purpose PNP bipolar junction transistor (BJT), widely used for low-current amplification and switching applications. It is often considered the PNP complement to the BC548.
💡 BC558 Product Detail
Core Function and Type
Type:PNP Bipolar Junction Transistor (BJT).
Function: It's used for small-signal amplification (e.g., pre-amplifier stages) and low-current switching. Because it's a PNP transistor, it's typically employed for high side switching, where the load is connected to the ground and the transistor switches the positive supply path.
Operating Principle: A small negative voltage/current applied to the Base (relative to the Emitter) turns it ON, allowing current to flow from the Emitter to the Collector.
Key Specifications
| Parameter | Typical Value | Description |
| Collector Current (I_C) | -100mA | the maximum continuous current it can switch. |
| Collector-Emitter Voltage (V_CE) | -30V | The maximum voltage it can withstand. |
| DC Current Gain (h_FE) | 110 to 800 | The ratio of Collector current to Base current (beta). |
| Power Dissipation (P_D) | 500mW | the maximum power it can safely dissipate. |
Note: The negative values reflect that PNP currents and voltages are typically referenced with respect to the Emitter being more positive.
Package and Pinout
Package: The BC558 is most often found in the plastic TO-92 through-hole package.
Pinout: When viewed from the flat side, the standard European pinout is:
Collector
Base
Emitter
Common Applications
Small-Signal Amplification: Used extensively in audio stages and general-purpose pre-amplifiers.
High-Side Switching: Suitable for controlling small loads connected to the ground, switching the power from the positive rail.
Complementary Circuits: Often paired with its NPN counterpart, the BC548, in various complementary circuits and push-pull configurations.