BC549 LOW NOISE NPN
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The BC549 is a highly popular, general-purpose NPN bipolar junction transistor (BJT), primarily known for its low-noise characteristics compared to similar transistors like the BC548 or BC547.
👂 BC549 Product Detail
Core Function and Type
Type:NPN Bipolar Junction Transistor (BJT).
Function: It is an excellent choice for small-signal pre-amplification where low noise is critical. Like other NPN transistors, it is used for low-current switching and amplification.
Operating Principle: A small positive current applied to the Base controls a larger current flow from the Collector to the Emitter.
Key Specifications
| Parameter | Typical Value | Description |
| Collector Current (I_C) | 100mA | the maximum continuous current the transistor can switch. |
| Collector-Emitter Voltage (V_CE) | 30V | The maximum voltage it can withstand. |
| DC Current Gain (h_FE) | 110 to 800 | The high ratio of Collector current to Base current (beta). |
| Noise Figure (NF) | 1.2dB (typical) | This is the defining feature; its low value indicates superior performance in reducing unwanted electrical noise. |
| Power Dissipation (P_D) | 500mW | the maximum power it can safely dissipate. |
Package and Pinout
Package: The BC549 is typically supplied 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
Due to its high gain and, most importantly, its low noise figure, the BC549 is preferred in sensitive applications:
Audio Preamplifiers: Used in the initial stages of audio circuits (like microphone preamps) to amplify the weak signal without introducing significant hiss or noise.
Instrumentation Amplifiers: Used in circuits designed to amplify small signals from sensors or transducers.
Low-Current Switching: Suitable for general-purpose, low-power switching applications, though the BC548 is often used here interchangeably.