Transistor NPN bc 548

🛠️ NPN Transistor – BC548 (TO‑92 Package)

Overview

The BC548 is a general-purpose silicon NPN transistor in a TO‑92 package, extensively used for switching and signal amplification in low-power electronics. It handles up to 100 mA and 30 V, making it a reliable choice for interfacing microcontrollers with LEDs, small relays, motor drivers, and audio circuits

Pinout (flat face forward, leads pointing down)

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1 = Collector | 2 = Base | 3 = Emitter

Typical Arduino Switching Circuit

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Arduino GPIO → 1 kΩ resistor → Base  
Emitter → Arduino GND  
Collector → Load → +V supply

Applications

• LED and small relay driving

• Audio preamplifiers and signal gain stages

• Digital switching and sensor interfacing

• Small motor control via PWM

• Oscillators and timing circuits 

✅ Resources

1. 📄 Datasheet: BC546/547/548 series (ON Semiconductor) – full specs: voltage ratings, gain curves, and pinouts etechnophiles.com+15mouser.com+15b-kainka.de+15

2. 🎥 YouTube Tutorial: “How to use the 2N3904/BC547 NPN transistor as a switch” – practical switching example with Arduino (applies to BC548) azadtechhub.com+1etechnophiles.com+1