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BC547 BC557 TO-92 NPN PNP Transistor Assorted Kit — 50 Pairs (100pcs)
BC547 BC557 TO-92 NPN PNP Transistor Assorted Kit 50 Pairs (100pcs)
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BC547 / BC557 TO-92 NPN & PNP Transistor Assorted Kit — 50 Pairs (100pcs)
A matched assorted kit of 50 pairs (100 pieces total) of BC547B NPN and BC557B PNP general-purpose TO-92 transistors. The BC547/BC557 complementary pair is one of the most widely used small-signal transistor pairs in electronics, suitable for signal switching, audio amplification, oscillator circuits, and general-purpose analogue and digital circuit design. The B-grade suffix indicates medium gain (hFE 200–450 for BC547B, 200–450 for BC557B), providing consistent performance across the kit.
Technical Specifications
| Parameter | BC547B (NPN) | BC557B (PNP) |
|---|---|---|
| Type | NPN | PNP |
| Package | TO-92 | TO-92 |
| V_CEO (max) | 45V | 45V |
| I_C (max) | 100mA | 100mA |
| P_D (max) | 500mW | 500mW |
| hFE (B grade) | 200–450 | 200–450 |
| f_T (transition freq.) | 300MHz | 150MHz |
| V_BE (sat) | ~0.7V | ~0.7V |
| Noise Figure | Low (audio grade) | Low (audio grade) |
| Certification | RoHS | |
BC547 vs BC548 vs BC549 Selection
| Part | V_CEO | Noise | Best For |
|---|---|---|---|
| BC547 | 45V | Low | General purpose, switching, audio |
| BC548 | 30V | Low | Low-voltage general purpose |
| BC549 | 30V | Very low | Low-noise audio preamplifier |
Typical Applications
- Signal Switching: BC547 as a digital signal switch — drive relay coils, LEDs, buzzers, and small loads from Arduino and microcontroller GPIO pins (up to 100mA)
- Audio Amplifier: BC547/BC557 complementary pair in Class A and Class AB audio preamplifier stages for microphone, phono, and line-level signal amplification
- Oscillator: BC547 in Colpitts, Hartley, and RC phase-shift oscillator circuits for signal generation
- Current Mirror: BC547/BC557 matched pair for precision current mirror circuits in analogue signal processing
- Push-Pull Output Stage: BC547/BC557 complementary emitter follower for low-power push-pull output stages in audio and signal circuits
- Arduino GPIO Expander: BC547 as a transistor switch to drive loads exceeding Arduino GPIO current limits (40mA max per pin)
FAQ
Q: What is the pinout of the BC547 and BC557 in TO-92 package?
A: Holding the flat face of the TO-92 package towards you with the leads pointing down: Left = Collector (C), Centre = Base (B), Right = Emitter (E). Note: some manufacturers use CBE, others use EBC — verify against the datasheet for your specific batch.
Q: Can I use BC547/BC557 to drive a relay directly from Arduino?
A: Yes. Connect the Arduino GPIO pin through a 1kΩ base resistor to the BC547 base. Connect the relay coil between the collector and 5V/12V supply. Add a flyback diode (1N4148) across the relay coil for inductive spike protection.
Package Contents
- 50 × BC547B NPN transistor (TO-92)
- 50 × BC557B PNP transistor (TO-92)
- Total: 100pcs
