Table of Contents
Introduction
The BC546 is an NPN bipolar junction transistor (BJT) that belongs to the BC546–BC550 family, designed for low current, low noise, and medium voltage applications. It is mainly used in audio amplification, signal processing, and switching circuits. The transistor can handle a maximum collector current (Ic) of 100 mA and a collector-emitter voltage (Vce) of 65 V, which is higher than that of its close relatives (BC547 and BC548). This makes the BC546 suitable for slightly higher voltage applications where stable performance is required.
It is widely preferred in analog and digital circuits, especially where signal clarity and low noise are critical. The BC546 is built using silicon planar epitaxial technology, which ensures consistent performance across temperature ranges and long-term stability. With its compact TO-92 package, it is easy to use in breadboards, prototyping, and PCB designs.
BC546 Pinout
| Pin Number | Pin Name | Description |
|---|---|---|
| 1 | Collector (C) | Current flows in through the collector terminal. |
| 2 | Base (B) | Controls transistor operation by applying small current. |
| 3 | Emitter (E) | Current flows out through the emitter terminal to ground. |
When viewed from the flat side of the TO-92 package, the pins are arranged as 1 – Collector, 2 – Base, 3 – Emitter.
Electrical Characteristics
| Parameter | Symbol | Value | Unit |
|---|---|---|---|
| Collector–Emitter Voltage | VCE | 65 | V |
| Collector–Base Voltage | VCB | 80 | V |
| Emitter–Base Voltage | VEB | 6 | V |
| Collector Current | IC | 100 | mA |
| DC Current Gain | hFE | 110–800 | — |
| Transition Frequency | fT | 150 | MHz |
| Power Dissipation | Ptot | 500 | mW |
| Junction Temperature | Tj | 150 | °C |
Features
- NPN Silicon Transistor
- Designed for low noise, medium voltage applications
- Maximum voltage rating: 65V (higher than BC547/BC548)
- Current gain (hFE): 110 to 800
- Suitable for audio and intermediate frequency (IF) stages
- Low leakage current ensures reliable performance
- Available in a TO-92 plastic package
- Operating temperature range: –65°C to +150°C
Equivalent / Alternative Transistors
| Equivalent Transistor | Type | Remarks |
|---|---|---|
| BC547 | NPN | Same family, lower voltage (45V) version |
| BC548 | NPN | Medium voltage, general-purpose use |
| 2N2222 | NPN | Higher current handling |
| 2N3904 | NPN | Common general-purpose transistor |
| S8050 | NPN | Similar gain range and low voltage operation |
Applications
- Low noise audio amplifier circuits
- Signal processing and small signal amplification
- Switching small loads or relays
- Sensor interface and detection circuits
- Oscillators and waveform generators
- Microcontroller output drivers
- Voltage regulation feedback circuits
Conclusion
The BC546 transistor is a robust and efficient component designed for medium voltage and low current operations. Its high voltage rating (65V) makes it ideal for signal amplification and switching applications where stability and noise reduction are important. As a member of the BC54x series, it is interchangeable with BC547 and BC548 for most low-power applications, offering engineers a reliable choice for analog and digital designs.
