BC548 NPN General-Purpose Transistor – 30V 100mA TO-92 Through-Hole Switching and Amplifier Transistor

The BC548 NPN transistor is a compact, general-purpose bipolar junction transistor designed for low-power switching, signal amplification and electronic control applications. It is widely used in DIY circuits, educational projects, audio preamplifiers, sensor circuits, LED controllers, relay driver stages and general electronic prototyping.

This transistor can be used as an electronic switch to control small loads from a low-current signal or as an amplifier for low-level analogue and audio signals. Its compact TO-92 through-hole package makes it easy to install on breadboards, prototype boards and printed circuit boards.

The BC548 supports a maximum collector-emitter voltage of approximately 30V, a continuous collector current of up to 100mA, and collector power dissipation of up to approximately 500mW, subject to operating and thermal conditions.

Different gain-group versions may be marked BC548A, BC548B or BC548C. These suffixes indicate different DC current-gain ranges. The exact gain and electrical characteristics may therefore vary according to the manufacturer and transistor marking.

Common Applications

• Small-signal amplification
• Low-current electronic switching
• LED switching circuits
• Buzzer driver circuits
• Sensor output circuits
• Audio preamplifier projects
• Microphone amplifier circuits
• Oscillator and timer circuits
• Arduino and microcontroller interfacing
• Relay driver stages with suitable protection
• Educational electronics experiments
• Breadboard and PCB prototyping
• Hobby and DIY electronic projects
• Signal-processing circuits
• Transistor-based logic circuits

Pin Configuration

For many BC548 transistors, when the flat face is held towards you and the pins point downward, the common pin order is:

Pin 1 – Collector
Pin 2 – Base
Pin 3 – Emitter

However, transistor pin arrangements can differ between manufacturers. Always verify the datasheet or test the component before connecting it to a circuit.